Rio Tinto (RIO) 20-F 4 Mar 19 2018 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2018shares
Document Information [Line Items]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	RIO
Entity Registrant Name	Rio Tinto plc
Entity Central Index Key	863,064
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	1,287,659,651
Rio Tinto Limited [member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	371,216,214

Group income statement

Group income statement - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated operations
Consolidated sales revenue	$ 40,522	$ 40,030	$ 33,781
Net operating costs (excluding items shown separately)	(27,115)	(26,983)	(26,799)
Impairment charges	(132)	(796)	(249)
Net gains on consolidation and disposal of interests in businesses	4,622	2,344	515
Exploration and evaluation costs	(488)	(445)	(497)
Profit/(loss) relating to interests in undeveloped projects	278	(15)	44
Operating profit	17,687	14,135	6,795
Share of profit after tax of equity accounted units	513	339	321
Profit before finance items and taxation	18,200	14,474	7,116
Finance items
Net exchange gains/(losses) on US external debt and intragroup balances	704	(601)	611
Net (losses)/gains on derivatives not qualifying for hedge accounting	(57)	33	(24)
Finance income	249	141	89
Finance costs	(552)	(848)	(1,111)
Amortisation of discount	(377)	(383)	(338)
Net finance income (expense)	(33)	(1,658)	(773)
Profit before taxation	18,167	12,816	6,343
Taxation	(4,242)	(3,965)	(1,567)
Profit after tax for the year	13,925	8,851	4,776
– attributable to owners of Rio Tinto (net earnings)	13,638	8,762	4,617
– attributable to non-controlling interests	$ 287	$ 89	$ 159
Basic earnings per share	$ 793.2	$ 490.4	$ 256.9
Diluted earnings per share	$ 787.6	$ 486.9	$ 255.3

Group statement of comprehensiv

Group statement of comprehensive income - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Comprehensive Income [Abstract]
Profit after tax for the year		$ 13,925	$ 8,851	$ 4,776
Items that will not be reclassified to profit or loss:
Actuarial gains/(losses) on post-retirement benefit plans		907	6	(90)
Changes in the fair value of equity investments held at fair value through other comprehensive income (FVOCI)		(13)
Tax relating to these components of other comprehensive income		(271)	(12)	29
Share of other comprehensive losses of equity accounted units, net of tax		(1)
Adjustments to deferred tax on post-retirement benefit plans due to changes in corporate tax rates in the US and France			(140)
Items that will not be reclassified to profit or loss		622	(146)	(61)
Items that have been/may be subsequently reclassified to profit or loss:
Currency translation adjustment	[1]	(3,830)	3,096	(157)
Currency translation on companies disposed of, transferred to the income statement		14	78	99
Fair value movements:
– Cash flow hedge gains/(losses)		156	62	(88)
– Cash flow hedge losses/(gains) transferred to the income statement		40	(62)	116
– Gains on revaluation of available for sale securities			19	13
– Losses on revaluation of available for sale securities transferred to the income statement			8	(167)
Net change in costs of hedging (b)		(39)
Tax relating to these components of other comprehensive income		(54)	(1)	4
Share of other comprehensive (loss)/income of equity accounted units, net of tax		(48)	34	11
Other comprehensive (loss)/income for the year, net of tax		(3,139)	3,088	(63)
Total comprehensive income for the year	[2]	10,786	11,939	4,713
– attributable to owners of Rio Tinto		10,663	11,691	4,504
– attributable to non-controlling interests		$ 123	$ 248	$ 209
[1]	Excludes a currency translation charge of US$382 million (2017: gain of US$310 million; 2016: charge of US$35 million) arising on Rio Tinto Limited’s share capital for the year ended 31 December 2018, which is recognised in the Group statement of changes in equity. Refer to Group statement of changes in equity on page 148.
[2]	Refer to Group statement of comprehensive income for further details. Adjustments to other reserves include currency translation attributable to owners of Rio Tinto, other than that arising on Rio Tinto Limited’s share capital.

Group statement of comprehens_2

Group statement of comprehensive income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	[1]	Dec. 31, 2016
Statement Of Comprehensive Income [Abstract]
Currency translation charge	$ (382)	[1]	$ 310		$ (35)
Reclassification of cost of hedging to income statement and recognised within finance costs	$ 3
[1]	Refer to note 1(d).

Group cash flow statement

Group cash flow statement - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Cash Flows [Abstract]
Cash flows from consolidated operations		$ 15,655	$ 16,670	$ 11,368
Dividends from equity accounted units		800	817	253
Cash flows from operations		16,455	17,487	11,621
Net interest paid	[1]	(612)	(897)	(1,294)
Dividends paid to holders of non-controlling interests in subsidiaries		(420)	(399)	(341)
Tax paid		(3,602)	(2,307)	(1,521)
Net cash generated from operating activities		11,821	13,884	8,465
Cash flows from investing activities
Purchases of property, plant and equipment and intangible assets		(5,430)	(4,482)	(3,012)
Disposals of subsidiaries, joint ventures, unincorporated joint operations, and associates		7,733	2,675	761
Purchases of financial assets	[2]	1,572	723	789
Sales of financial assets	[2]	19	40	582
Sales of property, plant and equipment and intangible assets		586	138	354
Net funding of equity accounted units		(9)	(3)	(12)
Acquisitions of subsidiaries, joint ventures and associates		(5)
Other investing cash flows		(1)	(18)	12
Net cash generated/(used) in investing activities		1,321	(2,373)	(2,104)
Cash flows before financing activities		13,142	11,511	6,361
Cash flows from financing activities
Equity dividends paid to owners of Rio Tinto		(5,356)	(4,250)	(2,725)
Proceeds from additional borrowings		54	18	4,413
Repayment of borrowings	[1]	(2,300)	(2,795)	(9,361)
Proceeds from issue of equity to non-controlling interests		85	170	101
Own shares purchased from owners of Rio Tinto		(5,386)	(2,083)
Purchase of non-controlling interests			(194)	(23)
Other financing cash flows		(48)	(7)	104
Net cash flows used in financing activities		(12,951)	(9,141)	(7,491)
Effects of exchange rates on cash and cash equivalents		151	(12)	(35)
Net increase/(decrease) in cash and cash equivalents		342	2,358	(1,165)
Opening cash and cash equivalents less overdrafts		10,547	8,189	9,354
Closing cash and cash equivalents less overdrafts		$ 10,889	$ 10,547	$ 8,189
[1]	(b)We completed a US$1.9 billion (nominal value) bond buy-back programme in April 2018. The notes purchased and redeemed have been cancelled. Net interest paid includes US$80 million being the payment of the premiums and the accelerated interest associated with the bond redemption. In 2017, we completed a US$2.5 billion (nominal value) bond buy-back programme. Net interest paid includes US$259 million being the payment of the premiums and the accelerated interest associated with the bond redemption. In 2016, Rio Tinto completed three bond purchase programmes totalling US$7.5 billion (nominal values). These transactions resulted in net interest paid of US$493 million, which represents the payment of the premiums and the accelerated interest associated with these bond redemptions.
[2]	During 2018, we invested US$1.6 billion (2017: US$0.7 billion) in a separately managed portfolio of fixed income instruments. As there was significant turnover in both years, we have elected to report the purchases and sales of these securities on a net cash flow basis within “Purchases of financial assets”. In 2016, the Group invested US$0.25 billion in these securities and reported the purchases and sales on a gross basis.

Group cash flow statement (Pare

Group cash flow statement (Parenthetical) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from consolidated operations
Profit after tax for the year		$ 13,925	$ 8,851	$ 4,776
Adjustments for:
– Taxation		4,242	3,965	1,567
– Finance items		33	1,658	773
– Share of profit after tax of equity accounted units		(513)	(339)	(321)
– Net gains on consolidation and disposal of interests in businesses		(4,622)	(2,344)	(515)
– Impairment charges		132	796	249
– Depreciation and amortisation		4,015	4,375	4,794
– Provisions (including exchange differences on provisions)		1,011	535	1,417
Utilisation of provisions		(620)	(714)	(627)
Utilisation of provision for post-retirement benefits		(219)	(339)	(370)
Change in inventories		(587)	(482)	292
Change in trade and other receivables		(421)	(138)	(794)
Change in trade and other payables		476	421	229
Other items	[1]	(1,197)	425	(102)
Cash flows from consolidated operations		15,655	16,670	11,368
Buy-back of bonds			2,500	7,500
Net interest paid associated with bond redemption		80	259	493
Purchases of financial assets	[2]	1,572	723	789
Adjustments for derivative contracts transacted and not designated for hedge relationship		288	(501)	29
Adjustments to add back gain on sale of surplus land at Kitmat		549
Revaluation of a financial asset			(8)	167
Fixed Income Instruments [member]
Adjustments for:
Purchases of financial assets		$ 1,600	$ 700	$ 250
[1]	Includes adjustments to add back mark-to-market gains of US$288 million (2017: losses of US$501 million; 2016: gains of US$29 million) mainly relating to derivative contracts transacted for operational purposes and not designated in a hedge relationship. This also includes adjustments to add back a gain of US$549 million on the sale of surplus land at Kitimat and a gain of US$167 million on the revaluation of a financial asset arising from the disposal of the Mount Pleasant coal project in 2016.
[2]	During 2018, we invested US$1.6 billion (2017: US$0.7 billion) in a separately managed portfolio of fixed income instruments. As there was significant turnover in both years, we have elected to report the purchases and sales of these securities on a net cash flow basis within “Purchases of financial assets”. In 2016, the Group invested US$0.25 billion in these securities and reported the purchases and sales on a gross basis.

Group balance sheet

Group balance sheet - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Non-current assets
Goodwill	$ 912	$ 1,037
Intangible assets	2,779	3,119
Property, plant and equipment	56,361	62,093
Investments in equity accounted units	4,299	4,486
Inventories	152	160
Deferred tax assets	3,137	3,395
Trade and other receivables	1,585	1,724
Tax recoverable	8	30
Other financial assets (including loans to equity accounted units)	814	510
Total non-current assets	70,047	76,554
Current assets
Inventories	3,447	3,472
Trade and other receivables	3,179	3,443
Tax recoverable	77	129
Other financial assets (including loans to equity accounted units)	2,692	1,084
Cash and cash equivalents	10,773	10,550
Total current assets	20,168	18,678
Assets of disposal groups held for sale	734	494
Total assets	90,949	95,726
Current liabilities
Borrowings and other financial liabilities	(1,073)	(904)
Trade and other payables	(6,600)	(7,061)
Tax payable	(1,842)	(1,985)
Provisions including post-retirement benefits	(1,056)	(1,275)
Total current liabilities	(10,571)	(11,225)
Non-current liabilities
Borrowings and other financial liabilities	(12,847)	(15,148)
Trade and other payables	(841)	(856)
Tax payable	(348)	(263)
Deferred tax liabilities	(3,673)	(3,628)
Provisions including post-retirement benefits	(12,552)	(13,367)
Total non-current liabilities	(30,261)	(33,262)
Liabilities of disposal groups held for sale	(294)	(124)
Total liabilities	(41,126)	(44,611)
Net assets	49,823	51,115
Capital and reserves
Share premium account	4,312	4,306
Other reserves	8,661	12,284
Retained earnings	27,025	23,761
Equity attributable to owners of Rio Tinto	43,686	44,711
Attributable to non-controlling interests	6,137	6,404
Total equity	49,823	51,115
Rio Tinto plc [member]
Capital and reserves
Share capital	211	220
Rio Tinto Limited [member]
Capital and reserves
Share capital	$ 3,477	$ 4,140

Group statement of changes in e

Group statement of changes in equity - USD ($) $ in Millions		Total	Share capital [member]	Share premium [Member]	Other reserves [Member]	Retained earnings [Member]	Total [member]	Non-controlling interests [Member]
Opening balance at Dec. 31, 2015		$ 44,128	$ 4,174	$ 4,300	$ 9,139	$ 19,736	$ 37,349	$ 6,779
Total comprehensive income for the year	[1]	4,713			(49)	4,553	4,504	209
Currency translation arising on Rio Tinto Limited's share capital		(35)	(35)				(35)
Dividends		(3,077)				(2,725)	(2,725)	(352)
Companies No Longer Consolidated		8						8
Own shares purchased from Rio Tinto shareholders to satisfy share options		(80)			(43)	(37)	(80)
Change in equity interest held by Rio Tinto	[2]	(165)			108	40	148	(313)
Treasury shares reissued and other movements		4		4			4
Equity issued to holders of non-controlling interests		109						109
Employee share options and other IFRS 2 charges to the income statement		125			61	64	125
Closing balance at Dec. 31, 2016		45,730	4,139	4,304	9,216	21,631	39,290	6,440
Total comprehensive income for the year	[1]	11,939			3,078	8,613	11,691	248
Currency translation arising on Rio Tinto Limited's share capital	[3]	310	310				310
Dividends		(4,653)				(4,250)	(4,250)	(403)
Share buy-back	[4]	(2,397)	(89)		4	(2,312)	(2,397)
Companies No Longer Consolidated		(2)			(124)	130	6	(8)
Own shares purchased from Rio Tinto shareholders to satisfy share options	[5]	(82)			(64)	(18)	(82)
Change in equity interest held by Rio Tinto						43	43	(43)
Treasury shares reissued and other movements		2		2			2
Equity issued to holders of non-controlling interests		170						170
Employee share options and other IFRS 2 charges to the income statement		98			41	57	98
Transfers and other movements					133	(133)
Closing balance at Dec. 31, 2017		51,115	4,360	4,306	12,284	23,761	44,711	6,404
Adjustment for transition to new accounting standards | Increase (decrease) due to changes in accounting policy required by IFRSs [Member]	[6]	(169)			10	(179)	(169)
Restated opening balance at Dec. 31, 2017		50,946	4,360	4,306	12,294	23,582	44,542	6,404
Total comprehensive income for the year	[1]	10,786			(3,600)	14,263	10,663	123
Currency translation arising on Rio Tinto Limited's share capital	[3]	(382)	(382)				(382)
Dividends		(5,771)				(5,356)	(5,356)	(415)
Share buy-back	[4]	(5,704)	(290)		9	(5,423)	(5,704)
Own shares purchased from Rio Tinto shareholders to satisfy share options	[5]	(254)			(114)	(140)	(254)
Change in equity interest held by Rio Tinto						60	60	(60)
Treasury shares reissued and other movements		6		6			6
Equity issued to holders of non-controlling interests		85						85
Employee share options and other IFRS 2 charges to the income statement		111			50	61	111
Transfers and other movements					22	(22)
Closing balance at Dec. 31, 2018		$ 49,823	$ 3,688	$ 4,312	$ 8,661	$ 27,025	$ 43,686	$ 6,137
[1]	Refer to Group statement of comprehensive income for further details. Adjustments to other reserves include currency translation attributable to owners of Rio Tinto, other than that arising on Rio Tinto Limited’s share capital.
[2]	The restructure of Coal & Allied Industries Limited completed on 3 February 2016. The restructure involved the exchange of a 32.4% interest in Hunter Valley Operations mine for an additional 20% shareholding in Coal & Allied Industries Limited, increasing Rio Tinto’s shareholding of Coal & Allied Industries Limited from 80% to 100%. Rio Tinto sold its 100% interest in Coal & Allied Industries Limited on 1 September 2017.
[3]	Refer to note 1(d).
[4]	In 2018, the total amount of US$5,704 million includes own shares purchased from the owners of Rio Tinto as per the cash flow statement of US$5,386 million and a financial liability recognised in respect of an irrevocable contract in place as at 31 December 2018 to cover the share buy-back programme, less amounts paid during the year in respect of a similar irrevocable contract in place at 31 December 2017. In 2017, the total amount of US$2,397 million includes own shares purchased from the owners of Rio Tinto as per the cash flow statement of US$2,083 million and a financial liability recognised in respect of the irrevocable contract in place as at 31 December 2017.
[5]	Net of contributions received from employees for share options.
[6]	The impact of the transition to new accounting standards; IFRS 9 “Financial Instruments” and IFRS 15 “Revenue from Contracts with Customers” on 1 January 2018 is discussed in note 45.

Group statement of changes in_2

Group statement of changes in equity (Parenthetical) $ in Millions	Feb. 03, 2016
Coal & Allied Industries Limited [member]
Additional ownership percentage acquired in subsidiary	20.00%
Ownership percentage in subsidiary	100.00%
Hunter valley operations [member]
Percentage of ownership interest exchanged in joint venture	32.40%

Principal accounting policies

Principal accounting policies	12 Months Ended
	Dec. 31, 2018
Disclosure Of Accounting Policies [Abstract]
Principal accounting policies	Corporate information Rio Tinto’s business is finding, mining and processing mineral resources. Major products are aluminium, copper, diamonds, gold, industrial minerals (borates, titanium dioxide and salt), iron ore and uranium. Activities span the world and are strongly represented in Australia and North America, with significant businesses also in Asia, Europe, Africa and South America. Rio Tinto plc is incorporated in the UK and listed on the London and New York Stock Exchanges and Rio Tinto Limited is incorporated in Australia and listed on the Australian Stock Exchange. Rio Tinto plc’s registered office is at 6 St James’s Square, London SW1Y 4AD, UK. Rio Tinto Limited’s registered office is at Level 7, 360 Collins Street, Melbourne, Victoria 3000, Australia. As described in the “Outline of dual listed companies structure and basis of financial statements” on page 149, for the purposes of preparing the IFRS compliant consolidated financial statements of the Rio Tinto Group, both the DLC companies, Rio Tinto plc and Rio Tinto Limited, are viewed as a single economic entity, and the interests of shareholders of both companies are presented as the equity interests of shareholders in the Rio Tinto Group. These financial statements consolidate the accounts of Rio Tinto plc and Rio Tinto Limited (together “the Companies”) and their respective subsidiaries (together “the Group”) and include the Group’s share of joint arrangements and associates as explained in note 1(b) below. The Group’s financial statements for the year ended 31 December 2018 were authorised for issue in accordance with a directors’ resolution on 27 February 2019. Notes 33 to 36 provide more information on the Group’s subsidiaries, joint arrangements and associates and note 40 provides information on the Group’s transactions with other related parties. The 2018 Annual report satisfies the obligations of Rio Tinto Limited to prepare consolidated accounts under Australian company law, as amended by an order issued by the Australian Securities and Investments Commission on 14 December 2015. The 2018 financial statements disclose on page 149 the effect of the adjustments to the Group’s consolidated profit/(loss), consolidated total comprehensive income/(loss) and consolidated shareholders’ funds as prepared under IFRS as defined below that would be required under the version of IFRS that is applicable in Australia, referred to as Australian Accounting Standards (AAS). The US dollar is the presentation currency used in these financial statements, as it most reliably reflects the Group’s global business performance. Basis of preparation of the financial statements The basis of preparation and the accounting policies used in preparing the Group’s 2018 financial statements are set out below. The financial statements have been prepared on a going concern basis in accordance with the Companies Act 2006 applicable to companies reporting under IFRS and in accordance with applicable UK law, applicable Australian law as amended by the Australian Securities and Investments Commission Order dated 14 December 2015, Article 4 of the European Union IAS regulation and also with: – International Financial Reporting Standards as issued by the International Accounting Standards Board (IASB) and interpretations issued from time to time by the IFRS Interpretations Committee (IFRS IC) both as adopted by the European Union (EU) and which are mandatory for EU reporting as at 31 December 2018; and – International Financial Reporting Standards as issued by the IASB and interpretations issued from time to time by the IFRS IC which are mandatory as at 31 December 2018. The above accounting standards and interpretations are collectively referred to as “IFRS” in this report. The Group has not early adopted any amendments, standards or interpretations that have been issued but are not yet mandatory. Further detail on the going concern basis of accounting is included on page 141. The Group’s financial statements have been prepared on the basis of accounting policies consistent with those applied in the financial statements for the year ended 31 December 2017, except for the change in accounting requirements set out below, all of which were effective as at 1 January 2018 without restatement of prior years. The Group adopted IFRS 9 “Financial Instruments”, IFRS 15 “Revenue from Contracts with Customers” and IFRIC 22 “Foreign Currency Transactions and Advance Consideration” and a number of other minor amendments to IFRS on 1 January 2018. All of these pronouncements have been endorsed by the EU. Information on the transition impact of these new pronouncements is included in note 45. Mandatory in 2019 The impact on the Group of transition to the accounting pronouncements listed below that are mandatory in 2019 is currently expected to be immaterial other than for IFRS 16 “Leases”. IFRS 16 “Leases” (Endorsed by the EU and mandatory in 2019) Under the new standard, a lessee is in essence required to: (a) Recognise all right of use assets and lease liabilities, with the exception of short-term (12 months or fewer) and low value leases, on the balance sheet. The lease liability is initially measured at the present value of future lease payments for the lease term. Where a lease contains an extension option, the lease payments for the extension period will be included in the liability if the Group is reasonably certain that it will exercise the option. The liability includes variable lease payments that depend on an index or rate but excludes other variable lease payments. The right of use asset at initial recognition reflects the lease liability, initial direct costs and any lease payments made before the commencement date of the lease less any lease incentives and, where applicable, provision for dismantling and restoration. (b) Recognise depreciation of right of use assets and interest on lease liabilities in the income statement over the lease term. (c) Separate the total amount of cash paid into a principal portion (presented within financing activities) and interest portion (which the Group presents in operating activities) in the cash flow statement. The Group will implement the standard as at 1 January 2019. For contracts in place at this date, the Group will continue to apply its existing definition of leases under current accounting standards (“grandfathering”), instead of reassessing whether existing contracts are or contain a lease at the date of application of the new standard. For transition, as permitted by IFRS 16, the Group will apply the modified retrospective approach to existing operating leases which will be capitalised under the new standard (ie retrospectively, with the cumulative effect recognised at the date of initial application as an adjustment to the opening balance of retained earnings with no restatement of comparative information in the financial statements). For existing finance leases, the carrying amounts before transition will represent the 31 December 2018 values assigned to the right of use asset and lease liability. The Group has made the following additional choices, as permitted by IFRS 16, for existing operating leases: – Not to bring short-term leases (12 months or fewer to run as at 1 January 2019 including reasonably certain options to extend) or low value leases on balance sheet. Costs for these items will continue to be expensed directly to the income statement. – For all leases, the lease liability will be measured at 1 January 2019 as the present value of any future lease payments discounted using the appropriate incremental borrowing rate. The carrying value of the right of use asset for property, vessels and certain other leases will generally be measured as if the lease had been in place since commencement date. For all other leases the right of use asset will be measured as equal to the lease liability and adjusted for any accruals or prepayments already on the balance sheet. The Group will also exclude any initial direct costs (eg legal fees) from the measurement of the right of use assets at transition. – An impairment review must be performed on right of use assets at initial application of the standard. The Group has elected to rely on its onerous lease assessments under IAS 37 “Provisions, Contingent Liabilities and Contingent Assets”, as at 31 December 2018 as permitted by IFRS 16. Any existing onerous lease provision is set against the right of use asset carrying value upon transition. – To apply the use of hindsight when reviewing the lease arrangements for determination of the measurement or term of the lease under the retrospective option. – To separate non-lease components from lease components for vessels and properties for the first time as part of the transition adjustment. – To continue not to apply lease accounting to intangible assets. – In some cases, to apply a single discount rate to a portfolio of leases with reasonably similar characteristics. The impact of transition to IFRS 16 on the Group’s 1 January 2019 balance sheet is expected to be an increase in lease liabilities (debt) of US$1.2 billion, an increase in right of use assets/net investments in leases of US$1.1 billion, net adjustments to other assets and liabilities of US$0.1 billion, and a charge of less than US$0.1 billion to retained earnings. The weighted average incremental borrowing rate applied to the Group’s lease liabilities to be recognised in the balance sheet at 1 January 2019 is 4.7%. The Group’s undiscounted non-cancellable operating lease commitments of US$1.7 billion at 31 December 2018 under IAS 17 “Leases” are shown on page 200 of this Report. The most significant differences between these lease commitments and a lease liability recorded on transition of US$1.3 billion as shown above are set out below: US$bn Operating lease commitments under IAS 17 per note 31 1.7 Exclude/deduct Leases expiring in 12 months or fewer (a) (0.1) Committed leases not commenced (a) (0.1) Components excluded from the lease liability (a) (0.2) Include/add Cost of reasonably certain extensions (a) 0.3 Other (b) 0.1 Sub total 1.7 Effect of discounting on payments included in the calculation of the lease liability (excluding finance lease balances) (0.4) Lease liability opening balance reported as at 1 January 2019 (IFRS 16) 1.3 (a) Undiscounted. (b) Includes finance lease liabilities already reported under IAS 17. Refer to note 23. The lease liability of US$1.3 billion (inclusive of amounts already reported as finance leases under IAS 17) shown above will be included in net debt as at 1 January 2019. The Group has implemented a lease accounting system which will be used for the majority of the Group’s leases. A separate contract linked system will be used for the Group’s shipping leases. Contracts signed after 1 January 2019 will be assessed against the lease identification criteria under IFRS 16. This may increase or decrease the number of contracts which are deemed to be leases. Practical application of IFRS 16 continues to develop and the Group continues to monitor this. In future periods EBITDA, as disclosed in the Financial Information by Business Unit on page 249 will increase as the operating lease cost is charged against EBITDA under IAS 17 whereas under IFRS 16 the charge will be included in depreciation and interest, which are excluded from EBITDA (although included in net earnings). Short-term leasing costs and non-lease components will continue to be charged against EBITDA. In 2018, an operating lease expense of US$787 million has been recorded in net operating costs; refer to note 4. This includes arrangements entered into and maturing during 2018 and therefore not disclosed as non-cancellable operating lease commitments at 31 December 2017. The Group has disclosed US$0.5 billion of non-cancellable operating lease commitments due within one year at 31 December 2018, approximately US$0.3 billion of which are not expected to be charged against EBITDA in 2019 as a result of implementing IFRS 16. Operating cash flows will increase under IFRS 16 as the element of cash paid attributable to the repayment of principal will be included in financing cash flows. The net increase/decrease in cash and cash equivalents will remain the same. The Group’s activities as a lessor are not material and hence the Group does not expect any significant impact on the financial statements. As the Group has some property sub lease arrangements, these must be reassessed for classification purposes as operating or finance leases at transition. Some additional disclosures will also be required from next year. IFRIC 23 “Uncertainty over Income Tax Treatments” (Endorsed by the EU and mandatory in 2019) IFRIC 23 changes the method of calculating provisions for uncertain tax positions. The Group currently recognises provisions based on the most likely amount of the liability, if any, for each separate uncertain tax position. The interpretation requires a probability weighted average approach to be taken for issues for which there are a wide range of possible outcomes. For tax issues with a binary outcome, the most likely amount method still remains. The interpretation must be implemented retrospectively, either with restatement of comparatives or with the cumulative impact of application recognised as at 1 January 2019 without restatement of comparatives. “Amendments to IFRS 9: Prepayment Features with Negative Compensation”, “Amendments to IAS 28: Long-term Interests in Associates and Joint Ventures” (Endorsed by the EU and mandatory in 2019), “Annual Improvements to IFRS Standards 2015-2017 Cycle” and “Amendments to IAS 19 – Plan Amendment, Curtailment or Settlement” (Mandatory in 2019 and not yet endorsed by the EU) The Group is currently evaluating the impact of these pronouncements. Mandatory in 2020 and beyond Conceptual Framework for Financial Reporting (Mandatory in 2020 and not yet endorsed by the EU) The 2018 Conceptual Framework for Financial Reporting is effective in 2020 for preparers that develop an accounting policy based on the Framework. The IASB revised its Conceptual Framework in April 2018. Where specific accounting policies are not covered by IFRS they must be in accordance with the principles in the Framework by 2020. The 2018 Conceptual Framework describes the objective of, and the concepts for, general purpose financial reporting. The purpose of the Conceptual Framework is to: a) Assist the International Accounting Standards Board (Board) to develop IFRS Standards (Standards) that are based on consistent concepts; b) Assist preparers to develop consistent accounting policies when no Standard applies to a particular transaction or other event, or when a Standard allows a choice of accounting policy; and c) Assist all parties to understand and interpret the Standards. The Conceptual Framework is not a Standard. Nothing in the Conceptual Framework overrides any Standard or any requirement in a Standard. The Group is currently evaluating this pronouncement. IFRS 17 “Insurance Contracts” (Mandatory in 2021 and not yet endorsed by the EU) The Standard provides consistent principles for all aspects of accounting for insurance contracts. The Group will evaluate the impact of this pronouncement in due course. Notes to the 2018 financial statements continued 1 Principal accounting policies continued Judgments in applying accounting policies and key sources of estimation uncertainty The preparation of the financial statements requires management to use judgment in applying accounting policies and in making critical accounting estimates. These judgments and estimates are based on management’s best knowledge of the relevant facts and circumstances, having regard to previous experience, but actual results may differ materially from the amounts included in the financial statements. Areas of judgment in the application of accounting policies that have the most significant effect on the amounts recognised in the financial statements and key sources of estimation uncertainty that have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next financial year are noted below and further information is contained in the accounting policies and/or the notes to the financial statements. These areas of judgment and estimation are discussed further in critical accounting policies and estimates on pages 162 to 164. The quantum of ore reserves and mineral resources impacts many of these areas and the basis of calculation is explained below. Information on less material judgments and sources of estimation uncertainty has been incorporated into the relevant accounting policy notes. Areas of judgment in the application of accounting policies that have the most significant effect on the amounts recognised in the financial statements are: – Impairment of non-current assets – determination of cash-generating units (CGUs) and assessment of indicators of impairment - note 1(e) and (i), note 6, note 12 and note 13. – Estimation of asset lives – whether certain assets are indefinite lived - note 1(e) and (i). – Provision for onerous contracts – determination of assets dedicated to a contract - note 1(i). – Close-down, restoration and environmental obligations – determining when an estimate is sufficiently reliable to update - note 1(k). – Deferral of stripping costs – judgment on components/strip ratios and separate or integrated multiple pit mines - note 1(h). – Uncertain tax positions – technical interpretation of tax law and the use of the most likely scenario for provision - note 1(m), note 9 and note 31. – Recoverability of potential deferred tax assets – recognition of deferred tax assets for loss-making operations - note 17(c), (e) and (f). – Identification of functional currencies – different companies may make different judgments based on similar facts - note 1(d). – Basis of consolidation – judgment as to when the Group has control, joint control or significant influence - notes 33 to 36. – Contingencies – assessing the probability of any loss and whether it is possible to quantify any loss - note 31. – Exclusions from underlying earnings – judgment on items to be excluded on grounds of nature or size - note 2. – Accounting for the Pilbara Arrangements – treatment of payments made over a contractually specified period for network infrastructure capacity - critical policies note (xiii). Key sources of estimation uncertainty that have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next financial year are: – Impairment of non-current assets - review of asset carrying values, impairment charges and reversals and the recoverability of goodwill – determination of discounted cash flows - note1(e) and (i), note 6, note 12 and note 13. – Provision for onerous contracts – cash flow estimates and the discount rate to be used - note 1(i). – Close-down, restoration and environmental cost obligations – estimation of costs and the timing of expenditure - note 1(k) and note 26. – Uncertain tax positions – estimating the potential exposures for each possible scenario - note 1(m), note 9 and note 31. – Recoverability of potential deferred tax assets – determination of cash flows - note 1(m), note 17(c), (e) and (f). – Estimation of obligations for post-employment costs - note 1(n) and note 44. – Contingencies – estimate of possible liability - note 31. Ore reserves and mineral resources Estimates of ore reserves and, in some cases, mineral resources can impact: depreciation and amortisation rates; the carrying values of intangible assets and property, plant and equipment; deferred stripping costs; provisions for close-down and restoration costs; and the recovery of deferred tax assets. The Group estimates its ore reserves and mineral resources based on information compiled by Competent Persons as defined in accordance with the Joint Ore Reserves Committee (JORC) code (see note 1(j)). The estimation of ore reserves and mineral resources requires judgment to interpret available geological data and subsequently to select an appropriate mining method and then to establish an extraction schedule. Estimation requires assumptions about future commodity prices and demand, exchange rates, production costs, transport costs, close-down and restoration costs, recovery rates and discount rates and, in some instances, the renewal of mining licences. There are many uncertainties in the estimation process and assumptions that are valid at the time of estimation may change significantly when new information becomes available. New geological or economic data, or unforeseen operational issues, may change estimates of ore reserves and mineral resources. The Group uses judgment as to when to include mineral resources in accounting estimates, for example, the use of mineral resources in the Group’s depreciation policy is described in note 1(i) below and in the determination of the date of closure as described in note 1(k). The unaudited statement of ore reserves is included on page 271 and of mineral resources on page 275. (a) Accounting convention The financial information included in the financial statements for the year ended 31 December 2018, and for the related comparative periods, has been prepared under the historical cost convention, as modified by the revaluation of certain derivative contracts and financial assets, the impact of fair value hedge accounting on the hedged item and the accounting for post-employment assets and obligations. The Group’s policy in respect of these items is set out in the notes below. All financial statement values are rounded to the nearest million (US$m) unless otherwise stated. Where applicable, comparatives have been adjusted to measure or present them on the same basis as current period figures. (b) Basis of consolidation (notes 33 to 36) All intragroup transactions and balances have been eliminated on consolidation. Where necessary, adjustments are made to the locally reported assets, liabilities, and results of subsidiaries, joint arrangements and associates to bring their accounting policies in line with those used by the Group. Subsidiaries: Subsidiaries are entities controlled by either of the Companies. Control exists where either of the Companies has: power over the entities, that is, existing rights that give it the current ability to direct the relevant activities of the entities (those that significantly affect the Companies’ returns); exposure, or rights, to variable returns from its involvement with the entities; and the ability to use its power to affect those returns. Subsidiaries are fully consolidated from the date on which the Group obtains control. They are deconsolidated from the date that control ceases. Joint arrangements: A joint arrangement is an arrangement in which two or more parties have joint control. Joint control is the contractually agreed sharing of control such that decisions about the relevant activities of the arrangement (those that significantly affect the Companies’ returns) require the unanimous consent of the parties sharing control. The Group has two types of joint arrangements: Joint operations (JO): A JO is a joint arrangement in which the parties that share joint control have rights to the assets, and obligations for the liabilities, relating to the arrangement. This includes situations where the parties benefit from the joint activity through a share of the output, rather than by receiving a share of the results of trading. In relation to its interest in a JO, the Group recognises: its share of assets and liabilities; revenue from the sale of its share of the output and its share of any revenue generated from the sale of the output by the JO; and its share of expenses. All such amounts are measured in accordance with the terms of the arrangement, which is usually in proportion to the Group’s interest in the JO. These amounts are recorded in the Group’s financial statements on the appropriate lines. Joint ventures (JV): A JV is a joint arrangement in which the parties that share joint control have rights to the net assets of the arrangement. JVs are accounted for using the equity accounting method. Other unincorporated arrangements: In some cases, the Group participates in unincorporated arrangements and has rights to its share of the assets and obligations for its share of the liabilities of the arrangement rather than a right to a net return, but does not share joint control. In such cases, the Group recognises: its share of assets and liabilities; revenue from the sale of its share of the output and its share of any revenue generated from the sale of the output by the unincorporated arrangement; and its share of expenses. All such amounts are measured in accordance with the terms of the arrangement, which is usually in proportion to the Group’s interest in the arrangement. These amounts are recorded in the Group’s financial statements on the appropriate lines. Associates: An associate is an entity that is neither a subsidiary nor a joint arrangement, over which the Group has significant influence. Significant influence is presumed to exist where there is neither control nor joint control and the Group has more than 20% of the voting rights, unless it can be clearly demonstrated that this is not the case. Significant influence can arise where the Group holds less than 20% of the voting rights if it has the power to participate in the financial and operating policy decisions affecting the entity. Investments in associates are accounted for using the equity accounting method . The Group uses the term “equity accounted units” (EAUs) to refer to associates and JVs collectively. Under the equity accounting method the investment is recorded initially at cost to the Group, including any goodwill on acquisition. In subsequent periods the carrying amount of the investment is adjusted to reflect the Group’s share of the EAUs’ retained post-acquisition profit or loss and other comprehensive income. Long-term loans to EAUs that in substance form part of the Group’s net investment (quasi equity loans) are financial assets but are included in the line “Investments in equity accounted units” on the face of the balance sheet. When the Group’s share of losses in an EAU equals or exceeds its interest in the EAU, including such long-term loans and any other unsecured receivables, the Group does not recognise further losses, unless it has incurred legal or constructive obligations to continue to make payments on behalf of the EAU. Acquisitions (note 37) Under the “acquisition” method of accounting for business combinations, the purchase consideration is allocated to the identifiable assets acquired and liabilities and contingent liabilities assumed (the identifiable net assets) on the basis of their fair value at the date of acquisition, which is the date on which control is obtained. The consideration transferred for the acquisition of a subsidiary comprises the fair values of the assets transferred, the liabilities incurred to the former owners of the acquiree, the fair value of any asset or liability resulting from a contingent consideration arrangement and any equity interests issued by the Group. Costs related to the acquisition of a subsidiary are expensed as incurred. The excess of the consideration transferred, the amount of any non-controlling interest in the acquiree and the acquisition date fair value of any previous equity interest in the acquiree over the fair value of the identifiable net assets acquired is recorded as goodwill. Any shortfall is immediately recognised in the income statement. Non-controlling interests in the acquiree, that are present ownership interests and entitle their holders to a proportionate share of the entity’s net assets in the event of liquidation, are recognised by the Group in one of two ways with the choice being available on an acquisition-by-acquisition basis. They can be measured at either the non-controlling interest’s proportionate share of the acquiree’s identifiable net assets or at fair value. In some cases, non-controlling interests may be treated as equity options and valued on that basis. Goodwill (see note (e)) and amounts attributable to non-controlling interests will differ depending on the basis used. Where the Group previously held a non-controlling interest in the acquiree, this is remeasured to fair value at the date control is obtained with any gain or loss recognised in the income statement. The cash cost of the share purchase that gives rise to control is included within “Investing activities” in the cash flow statement. Where the Group increases its ownership interest in a subsidiary, the difference between the purchase price and the carrying value of the share of net assets acquired is recorded in equity. The cash cost of such purchases is included within “Financing activities” in the cash flow statement. Provisional fair values allocated at a reporting date are finalised within 12 months of the acquisition date. The results of businesses acquired during the year are included in the consolidated financial statements from the date on which control, joint control or significant influence is obtained. Disposals (note 37) Individual non-current assets or “disposal groups” (that is, groups of assets and liabilities) to be disposed of by sale or otherwise in a single transaction are classified as “held for sale” if the following criteria are met at the period end: – T he carrying amount will be recovered principally through a sale transaction rather than through continuing use; and – The disposal group is available for immediate sale in its present condition subject only to terms that are usual and customary for such sales; and – The sale is highly probable. Disposal groups held for sale are carried at the lower of their carrying amount and fair value less costs to sell. The comparative balance sheet is not restated. Disposal groups acquired with a view to resale are held at the fair value determined at the acquisition date. For these assets acquired for resale no profits or losses are recognised between the acquisition date and the disposal date, unless there is a subsequent impairment. On classification as held for sale, the assets are no longer depreciated and, if applicable, equity accounting ceases. If control is lost, any interest in the entity retained by the Group is remeasured to its fair value and the change in carrying amount is recognised in the income statement. The retained interest may be subsequently accounted for as a joint venture, joint operation, associate or financial asset depending on the facts. Certain amounts previously recognised in other comprehensive income in respect of the entity disposed of, or for which control, joint control or significant influence has ceased, may be recycled to the income statement. The cash proceeds of disposals are included within “Investing activities” in the cash flow statement. Changes in the Group’s interest in a subsidiary that do not result in a loss of control are accounted for in equity. The cash proceeds of such disposals are included within “Financing activities” in the cash flow statement. (c) Sales revenue Recognition and measurement The Group recognises sales revenue related to the transfer of promised goods or services when control of the goods or services passes to the customer. The amount of revenue recognised reflects the consideration to which the Group is or expects to be entitled in exchange for those goods or services. Notes to the 2018 financial statements continued 1 Principal accounting policies continued Sales revenue is recognised on individual sales when control transfers to the customer. In most instances, control passes and sales revenue is recognised when the product is delivered to the vessel or vehicle on which it will be transported once loaded, the destination port or the customer’s premises. There may be circumstances when judgment is required based on the five indicators of control below. – The customer has the significant risks and rewards of ownership and has the ability to direct the use of, and obtain substantially all of the remaining benefits from, the goods or service. – The customer has a present obligation to pay in accordance with the terms of the sales contract. For shipments under the Incoterms Cost, Insurance and Freight (CIF)/Carriage Paid to (CPT)/Cost and Freight (CFR) this is generally when the ship is loaded, at which time the obligation for payment is for both product and freight. – The cust

Operating segments

Operating segments	12 Months Ended
	Dec. 31, 2018
Disclosure Of Operating Segments [Abstract]
Operating segments	Rio Tinto’s management structure is based on the principal product groups in the tables below together with the global functions that support the business, which include Growth & Innovation. The chief executive of each product group reports to the chief executive of Rio Tinto. The chief executive of Rio Tinto monitors the performance of each product group based on a number of measures, including underlying earnings, underlying EBITDA, capital expenditure, operating cash flow and free cash flow. Finance costs and net debt are managed on a Group basis. Generally, business units are allocated to product groups based on their primary product. The Energy & Minerals product group includes businesses with products such as uranium, borates, salt and titanium dioxide feedstock together with coal operations (prior to the divestment of these assets), Iron Ore Company of Canada and the Simandou iron ore project, which is the responsibility of the Energy & Minerals product group chief executive. The Copper & Diamonds product group also produces gold, silver, molybdenum and other by-products. The financial information by business unit provided on pages 249 to 251 of these financial statements provides additional voluntary disclosure which the Group considers useful to the users of the financial statements. 2018 2017 2016 Gross sales revenue US$m US$m US$m Iron Ore 18,485 18,251 14,605 Aluminium 12,191 11,005 9,458 Copper & Diamonds 6,468 4,842 4,524 Energy & Minerals 5,697 7,764 6,734 Other Operations 9 10 8 Reportable segments total 42,850 41,872 35,329 Inter-segment transactions (15 ) (15 ) (11 ) Product group total 42,835 41,857 35,318 Items excluded from underlying earnings - 10 18 Gross sales revenue 42,835 41,867 35,336 Share of equity accounted unit sales and adjustments for intra-subsidiary/equity accounted units sales (2,313 ) (1,837 ) (1,555 ) Consolidated sales revenue per income statement 40,522 40,030 33,781 Gross sales revenue includes the Group’s proportionate share of sales revenue of equity accounted units (after adjusting for sales to subsidiaries) of US$2,354 million (2017: US$1,859 million; 2016: US$1,585 million) which are not included in consolidated sales revenue. Consolidated sales revenue includes subsidiary sales of US$41 million (2017: US$22 million; 2016: US$30 million) to equity accounted units which are not included in gross sales revenue. 2018 2017 2016 Capital expenditure US$m US$m US$m Iron Ore 1,288 1,201 868 Aluminium 1,373 1,436 916 Copper & Diamonds 2,150 1,622 1,441 Energy & Minerals 456 467 141 Other Operations 12 (35 ) (11 ) Reportable segments total 5,279 4,691 3,355 Other items 65 70 (46 ) Less: capital expenditure of equity accounted units (500 ) (417 ) (651 ) Capital expenditure per financial information by business unit 4,844 4,344 2,658 Add back: proceeds from disposal of property, plant and equipment 586 138 354 Capital expenditure per cash flow statement 5,430 4,482 3,012 Capital expenditure for reportable segments comprises the net cash outflow on purchases less disposals of property, plant and equipment, capitalised evaluation costs and purchases less disposals of other intangible assets. The details provided include 100% of subsidiaries’ capital expenditure and Rio Tinto’s share of the capital expenditure of joint operations and equity accounted units. 2018 2017 2016 Depreciation and amortisation US$m US$m US$m Iron Ore 1,682 1,645 1,645 Aluminium 1,122 1,199 1,250 Copper & Diamonds 1,317 1,452 1,601 Energy & Minerals 475 652 739 Other Operations 26 32 34 Reportable segments total 4,622 4,980 5,269 Other items 43 42 51 Less: depreciation and amortisation of equity accounted units (650 ) (647 ) (526 ) Depreciation and amortisation per note 4 4,015 4,375 4,794 Product group depreciation and amortisation for reportable segments totals include 100% of subsidiaries’ depreciation and amortisation and Rio Tinto’s share of the depreciation and amortisation of equity accounted units. Rio Tinto’s share of the depreciation and amortisation charge of equity accounted units is deducted to arrive at depreciation and amortisation, excluding equity accounted units, as shown in note 4. These figures exclude impairment charges and reversals, which are excluded from underlying earnings. 2018 2017 2016 Tax charge/(credit) US$m US$m US$m Iron Ore 2,819 2,871 2,005 Aluminium 532 543 171 Copper & Diamonds 118 48 (320 ) Energy & Minerals 511 652 331 Other Operations (51 ) (84 ) (73 ) Reportable segments total 3,929 4,030 2,114 Other items (276 ) (261 ) (191 ) Exploration and evaluation not attributed to product groups (38 ) (36 ) (27 ) Net finance costs (174 ) (364 ) (484 ) 3,441 3,369 1,412 Tax charge excluded from underlying earnings 801 596 155 Tax charge per income statement 4,242 3,965 1,567 Tax charge/(credit) excludes amounts relating to equity accounted units. Further information on the tax charge/(credit) excluded from underlying earnings is provided in the section “Underlying earnings”, below. 2018 2017 2016 Underlying EBITDA US$m US$m US$m Iron Ore 11,325 11,520 8,526 Aluminium 3,095 3,423 2,472 Copper & Diamonds 2,776 1,904 1,387 Energy & Minerals 2,193 2,803 1,806 Other Operations (70 ) (116 ) (95 ) Reportable segments total 19,319 19,534 14,096 Central pension costs, share-based payments and insurance (128 ) (68 ) (34 ) Restructuring, project and one-off costs (272 ) (177 ) (13 ) Central costs (552 ) (491 ) (364 ) Exploration and evaluation not attributed to product groups (231 ) (218 ) (175 ) Underlying EBITDA 18,136 18,580 13,510 Items excluded from underlying EBITDA 5,127 1,912 (687 ) EBITDA 23,263 20,492 12,823 Depreciation, amortisation and impairment charges in subsidiaries and equity accounted units (4,691 ) (5,746 ) (5,466 ) Taxation and finance items in equity accounted units (372 ) (272 ) (241 ) Profit on ordinary activities before finance items and tax 18,200 14,474 7,116 Notes to the 2018 financial statements continued 2 Operating segments continued 2018 2017 2016 Underlying earnings US$m US$m US$m Iron Ore 6,514 6,692 4,611 Aluminium 1,347 1,583 947 Copper & Diamonds 1,054 263 (18 ) Energy & Minerals 1,012 1,242 612 Other Operations (102 ) (138 ) (88 ) Reportable segments total 9,825 9,642 6,064 Central pension costs, share-based payments and insurance (90 ) (48 ) (24 ) Restructuring, project and one-off costs (190 ) (124 ) (9 ) Central costs (410 ) (311 ) (208 ) Exploration and evaluation not attributed to product groups (193 ) (178 ) (147 ) Net finance costs (134 ) (354 ) (576 ) Underlying earnings 8,808 8,627 5,100 Items excluded from underlying earnings 4,830 135 (483 ) Net earnings attributable to owners of Rio Tinto per income statement 13,638 8,762 4,617 Underlying EBITDA and underlying earnings are reported by Rio Tinto to provide greater understanding of the underlying business performance of its operations and to enhance comparability of reporting periods. The measures of underlying EBITDA and underlying earnings, in conjunction with net cash generated from operating activities and capital expenditure (net of proceeds on disposals), are used by the chief executive of Rio Tinto to assess the performance of the product groups. Underlying earnings and net earnings both represent amounts net of tax attributable to owners of Rio Tinto. The following items are excluded from net earnings in arriving at underlying earnings in each period irrespective of materiality: – Net gains/(losses) on disposal of interests in businesses. – Impairment charges and reversals. – Profit/(loss) after tax from discontinued operations. – Exchange and derivative gains and losses. This exclusion includes exchange gains/(losses) on US dollar net debt and intragroup balances, unrealised gains/(losses) on currency and interest rate derivatives not qualifying for hedge accounting, unrealised gains/(losses) on certain commodity derivatives not qualifying for hedge accounting, and unrealised gains/(losses) on embedded derivatives not qualifying for hedge accounting. In addition, there is a final judgmental category which includes, where applicable, other credits and charges that, individually or in aggregate if of a similar type, are of a nature or size to require exclusion in order to provide additional insight into underlying business performance. Underlying EBITDA excludes the EBITDA impact of the same items that are excluded from underlying earnings. Product group earnings include earnings of subsidiaries and the Group’s share of the underlying earnings of equity accounted units stated before finance items but after the amortisation of discount on provisions. Rio Tinto’s share of the underlying earnings of equity accounted units amounted to US$513 million in 2018 (2017: US$332 million; 2016: US$309 million). This amount is attributable as follows: US$476 million profit to the Copper & Diamonds product group and US$38 million profit to other product groups (2017: US$295 million profit to the Copper & Diamonds product group and US$37 million profit to other product groups; 2016: US$272 million profit to the Copper & Diamonds product group and US$37 million profit to other product groups). These amounts are included in underlying earnings and include the underlying earnings of the Group’s tolling entities which process alumina. Tolling entities recharge the majority of their costs and generally have minimal earnings. Reconciliation of net earnings/(losses) to underlying earnings Non- controlling Net Net Net Pre-tax (m) Taxation interests amount amount amount 2018 2018 2018 2018 2017 2016 Exclusions from underlying earnings US$m US$m US$m US$m US$m US$m Impairment charges (note 6) (132 ) 25 3 (104 ) (481 ) (183 ) Net gains on consolidation and disposal of interests in businesses (a) 4,622 (626 ) - 3,996 2,022 382 Exchange and derivative gains/(losses): – Exchange gains/(losses) on US dollar net debt, intragroup balances and derivatives (b) 694 (136 ) (8 ) 550 (488 ) 516 – (Losses)/gains on currency and interest rate derivatives not qualifying for hedge accounting (c) (59 ) 11 - (48 ) 30 (12 ) – Gains/(losses) on embedded commodity derivatives not qualifying for hedge accounting (d) 288 (83 ) (3 ) 202 (352 ) 32 Losses from increases to closure estimates (non-operating and fully impaired sites) (e) (376 ) 41 - (335 ) - (282 ) Gain relating to surplus land at Kitimat (f) 602 (33 ) - 569 - - Changes in corporate tax rates in the US and France (g) - - - - (439 ) - Onerous port and rail contracts (h) - - - - - (329 ) Restructuring costs and global headcount reductions - - - - - (177 ) Rio Tinto Kennecott insurance settlement (i) - - - - 45 - Tax provision (j) - - - - - (380 ) Tax charge relating to expected divestments (k) - - - - (202 ) - Other exclusions (l) - - - - - (50 ) Total excluded from underlying earnings 5,639 (801 ) (8 ) 4,830 135 (483 ) Net earnings 18,167 (4,242 ) (287 ) 13,638 8,762 4,617 Underlying earnings 12,528 (3,441 ) (279 ) 8,808 8,627 5,100 (a) On 10 May 2018, Rio Tinto and Alcoa announced they had launched a new joint venture, Elysis, to develop and commercialise a carbon-free aluminium smelting process. Rio Tinto’s interest in the joint venture In 2017, the net gain related mainly to the sale of Coal & Allied Industries Limited, which completed on 1 September 2017. In 2016, the net gain related mainly to the sale of Rio Tinto’s 40% interest in the Bengalla Joint Venture on 1 March 2016 and the sale of the Lochaber assets in Scotland on 23 November 2016. This was partially offset by a loss on disposal of the 100% interest in Carbone Savoie on 31 March 2016. (b) Exchange gains/(losses) on external US dollar net debt and intragroup balances comprise of post-tax foreign exchange losses on US dollar denominated net debt in non-US dollar functional currency companies of US$386 million loss and post-tax gains of US$936 million on intragroup balances, primarily as a result of the Australian and Canadian dollars both weakening against the US dollar. Net exchange gains in 2017 comprise post-tax foreign exchange gains of US$420 million on US dollar denominated net debt, and US$908 million losses on intragroup balances. Net exchange gains in 2016 comprise post-tax foreign exchange gains of US$123 million on external US dollar denominated net debt, and US$393 million gains on intragroup balances, mainly as the Canadian dollar strengthened against the US dollar. (c) Valuation changes on currency and interest rate derivatives, which are ineligible for hedge accounting, other than those embedded in commercial contracts, and the currency revaluation of embedded US dollar derivatives contained in contracts held by entities whose functional currency is not the US dollar. (d) Valuation changes on derivatives, embedded in commercial contracts, that are ineligible for hedge accounting, but for which there will be an offsetting change in future Group earnings. From 1 January 2018, all mark-to-market movements on commodity derivatives entered into with the commercial objective of achieving spot pricing for the underlying transaction at the date of settlement are now included within underlying earnings. In 2017 and previous years, valuation changes on this type of commodity derivative were excluded from underlying earnings. The impact of this change on the reported comparatives is insignificant, and therefore the comparatives have not been restated. (e) been recognised in the income statement. The impairment charge in respect of Argyle recognised in 2017 (see note 6) was based on preliminary findings from the prefeasibility study. On this basis, the charge arising from the finalisation of this study in 2018 of US$134 million (US$93 million after tax) has been excluded from underlying earnings. On 6 December 2018, Energy Resources of Australia (ERA) (68% owned by Rio Tinto and listed on the Australian Stock Exchange) announced a likely increase to its closure provision of A$296 million pending finalisation of the Ranger Project Area closure feasibility study. The final assessment has indicated an increase equivalent to US$242 million. As the assets of ERA have been fully impaired, this increase has not been capitalised and has instead been recognised in the income statement. There is no tax impact in respect of this item. In 2016, the closure provision for non-operating and legacy operations increased mainly due to the Gove alumina refinery in Northern Territory, Australia where operations have been curtailed since May 2014. The provision was updated based on the cost estimates from the studies. Future revisions to the closure cost estimate during the study periods (including the next stage of feasibility study) will continue to be excluded from underlying earnings as the site operating assets have been fully impaired. (f) In November 2018, Rio Tinto completed the lease and sale of a wharf and land in Kitimat. This resulted in a pre-tax gain of US$549 million on disposal of Property, plant and equipment and Other income of US$53 million (total impact of US$569 million after tax). This has been excluded from underlying earnings on the grounds of materiality. (g) In 2017, deferred tax assets were remeasured to reflect lower corporate income tax rates in the US and France as a result of tax legislation changes substantively enacted in December 2017. (h) In 2016, a review of the infrastructure capacity requirements in Queensland, Australia, confirmed that it was no longer likely that Rio Tinto would utilise the Abbot Point Coal Terminal and associated rail infrastructure capacity contracted under take or pay arrangements, and agreement was reached with Adani, the owner of the port, to relinquish that capacity. Accordingly, an onerous contract provision was recognised based on the net present value of expected future cash flows for the port and rail capacity discounted at a post-tax real rate of 2%, resulting in a post-tax onerous contract charge of US$329 million. (i) In 2017, Rio Tinto received the final settlement on the insurance claims related to the 2013 slide at Rio Tinto Kennecott’s Bingham Canyon mine. The amounts excluded from underlying earnings were consistent with the previous excluded losses to which they related, in line with the treatment of the 2013 and 2015 settlement payments. (j) Tax provision includes amounts provided for specific tax matters for which the timing of resolution and potential economic outflow are uncertain. During 2016, provision was made in relation to matters under discussion with the Australian Taxation Office (ATO) in relation to the transfer pricing of certain transactions between Rio Tinto entities based in Australia and the Group’s commercial centre in Singapore for the period since 2009. (k) In 2017, deferred tax assets were derecognised as a result of revised profit forecasts in France due to the expected divestments of Dunkerque and ISAL. The Dunkerque divestment completed in 2018. (l) Other credits and charges that, individually, or in aggregate if of similar type, are of a nature or size to require exclusion in order to provide additional insight into underlying business performance. In 2016, other exclusions included costs related to multiple transformation projects and the recuperation of capital losses against capital gains on divestment. (m) Exclusions from underlying earnings relating to equity accounted units are stated after tax and are included in the column “Pre-tax”.

Operating segments - additional

Operating segments - additional information	12 Months Ended
	Dec. 31, 2018
Disclosure Of Operating Segments [Abstract]
Disclosure of entity's operating segments [text block]	Notes to the 2018 financial statements continued 2018 2017 2016 2018 2017 2016 Consolidated sales revenue by destination (a) % % % US$m US$m US$m China 44.6 44.2 43.6 18,061 17,706 14,742 Asia (excluding China and Japan) 11.5 12.8 13.9 4,665 5,108 4,692 United States of America 15.5 14.3 13.9 6,278 5,716 4,709 Japan 9.6 11.7 11.3 3,873 4,701 3,809 Europe (excluding UK) 9.1 7.5 7.6 3,706 3,015 2,579 Canada 3.2 2.8 3.0 1,340 1,111 1,024 Australia 1.8 1.8 2.0 720 710 675 UK 1.0 1.1 1.2 386 449 391 Other countries 3.7 3.8 3.5 1,493 1,514 1,160 Consolidated sales revenue 100.0 100.0 100.0 40,522 40,030 33,781 (a) Consolidated sales revenue by geographical destination is based on the ultimate country of destination of the product, if known. If the eventual destination of the product sold through traders is not known then revenue is allocated to the location of the product at the time when control is transferred. Rio Tinto is domiciled in both the UK and Australia. Consolidated sales revenue by product Consolidated sales revenues of the Group are derived from the following products sold to external customers: Revenue from contracts with customers Other revenue (a) Consolidated sales revenue Consolidated sales revenue Consolidated sales revenue 2018 2018 2018 2017 2016 US$m US$m US$m US$m US$m Iron ore 19,888 (21 ) 19,867 20,010 15,855 Aluminium 12,041 (22 ) 12,019 10,864 9,342 Copper 2,420 (32 ) 2,388 1,760 1,609 Coal 986 3 989 2,822 2,567 Industrial minerals 2,093 - 2,093 2,060 1,954 Gold 869 - 869 378 608 Diamonds 695 - 695 706 613 Other 1,602 - 1,602 1,430 1,233 Consolidated sales revenue 40,594 (72 ) 40,522 40,030 33,781 Share of equity accounted unit sales and intra-subsidiary/equity accounted unit sales 2,313 1,837 1,555 Gross sales revenue 42,835 41,867 35,336 (a) Certain of the Group’s products may be provisionally priced at the date revenue is recognised. The change in value of the provisionally priced receivables is based on relevant forward market prices and is included in “Other revenue” above. In prior periods there was no equivalent requirement under IAS 18 to separate out such provisional price movements and therefore this was not separately disclosed. Non-current assets other than excluded items (a) The total of non-current assets other than items excluded is shown by location below. This is allocated based on the location of the business units holding the assets. Adjusted (b) 2018 2017 US$m US$m Australia 28,592 32,890 Canada 13,775 14,822 Mongolia 9,912 8,582 United States of America 4,815 4,812 Africa 3,476 3,781 South America 3,047 3,304 Indonesia - 1,458 Europe (excluding France and the UK) 50 362 UK 59 66 France 79 94 Other countries 850 892 64,655 71,063 Non-current assets excluded from analysis above: Deferred tax assets 3,137 3,395 Other financial assets (including loans to equity accounted units) 814 510 Quasi equity loans to equity accounted units (c) 129 159 Tax recoverable 8 30 Trade and other receivables 1,304 1,397 Total non-current assets per balance sheet 70,047 76,554 (a) Allocation of non-current assets by country is based on the location of the business units holding the assets. It includes investments in equity accounted units totalling US$4,170 million (2017: US$4,327 million) which represents the Group’s share of net assets excluding quasi equity loans shown separately within “Loans to equity accounted units” above. (b) The 2017 comparatives above have been amended to correct the allocation of non-current assets other than excluded items by location. The impact is an increase in the amounts allocated to Canada and a decrease to the amounts allocated to France of US$182 million. There is no impact on the total non-current assets. (c) Loans to equity accounted units comprise quasi equity loans of US$129 million (2017: US$159 million) included in “Investments in equity accounted units” on the face of the balance sheet and non-current non-quasi equity loans of US$38 million (2017: US$39 million) shown within “Other financial assets”.

Net operating costs (excluding

Net operating costs (excluding items shown separately)	12 Months Ended
	Dec. 31, 2018
Net Operating Costs Excluding Items Shown Separately [Abstract]
Net operating costs (excluding items shown separately)	2018 2017 2016 Note US$m US$m US$m Raw materials, consumables, repairs and maintenance 10,613 9,286 8,760 Amortisation of intangible assets 13 133 177 227 Depreciation of property, plant and equipment 14 3,882 4,198 4,567 Employment costs 5 4,728 4,765 4,881 Shipping and other freight costs (a) 2,580 2,338 1,454 (Increase)/decrease in finished goods and work in progress (186 ) (82 ) 87 Royalties 2,117 2,228 1,889 Amounts charged by equity accounted units (b) 1,200 980 1,184 Net foreign exchange (gains)/losses (56 ) 61 38 Other external costs (a) (c) 3,184 3,967 3,512 Gain on sale of property, plant and equipment (d) (506 ) (32 ) (40 ) Provisions (including exchange differences on provisions) 26 1,011 527 1,404 Research and development 45 58 60 Costs included above qualifying for capitalisation (589 ) (486 ) (521 ) Other operating income (1,041 ) (1,002 ) (703 ) Net operating costs (excluding items shown separately) 27,115 26,983 26,799 (a) Net operating costs includes operating lease expense of US$787 million (2017: US$555 million, 2016: US$541 million). Costs for leases of dry bulk vessels (which include costs for crewing services) are included within “Shipping and other freight costs” and other lease costs are included within “Other external costs”. The Group will implement IFRS 16 “Leases” as at 1 January 2019; refer to note 1. (b) Amounts charged by equity accounted units relate to toll processing and also include purchases from equity accounted units of bauxite and aluminium which are then processed by the product group or sold to third parties. Generally, purchases are in proportion to the Group’s share of the equity accounted unit but in 2018, US$332 million (2017: US$229 million; 2016: US$383 million) related to purchases of the other investors’ share of production. (c) In 2017, other external costs include a financial penalty of £27.4 million (US$36.4 million) paid to the United Kingdom’s Financial Conduct Authority (FCA) in relation to the timing of the impairment of the Group’s former coal operations in Mozambique. Refer to note 31 for further detail. (d) Includes a pre-tax gain of US$549 million from the sale of property, plant and equipment at Kitimat. Refer to note 2.

Employment costs

Employment costs	12 Months Ended
	Dec. 31, 2018
Disclosure Of Employee Cost Explanatory [Abstract]
Employment costs	2018 2017 2016 Note US$m US$m US$m Total employment costs – Wages and salaries 4,154 4,129 4,235 – Social security costs 336 337 429 – Net post-retirement charge 44 532 500 522 – Share-based payment charge 43 122 91 116 5,144 5,057 5,302 Less: charged within provisions (a) 26 (416 ) (292 ) (421 ) Total employment costs 4 4,728 4,765 4,881 (a) Amounts included above in respect of provisions for pensions, post-retirement healthcare, long service leave and other employee entitlements which are included in “Provisions (including exchange differences on provisions)” in note 4.

Impairment charges

Impairment charges	12 Months Ended
	Dec. 31, 2018
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Abstract]
Impairment charges	Non- controlling Net Pre-tax Pre-tax Pre-tax Taxation interests amount amount amount 2018 2018 2018 2018 2017 2016 Note US$m US$m US$m US$m US$m US$m Aluminium – (123 ) 25 - (98 ) - - Energy & Minerals – Rössing (9 ) - 3 (6 ) (267 ) - Energy & Minerals – Roughrider - - - - (357 ) - Copper & Diamonds – Argyle - - - - (172 ) (241 ) Other - - - - - (8 ) Total impairment charge (132 ) 25 3 (104 ) (796 ) (249 ) Allocated as: Goodwill 12 - - - Intangible assets 13 (2 ) (357 ) (1 ) Property, plant and equipment 14 (130 ) (435 ) (248 ) Other assets and liabilities - (4 ) - Total impairment charge (132 ) (796 ) (249 ) Comprising: Total impairment charge net of reversals in the financial information by business unit ( page 249 (132 ) (796 ) (249 ) Taxation (including related to EAUs) 25 141 66 Non-controlling interests 3 174 - Total impairment in the income statement (104 ) (481 ) (183 ) Aluminium – ISAL Smelter In 2018, we reached agreement to sell the ISAL Dmelter in Iceland, our 53.3% interest in the Aluchemie anode plant in the Netherlands and our 50% share in the Aluminium fluoride plant in Sweden. The anticipated headline sales price of US$345 million was lower than the carrying value of these assets leading us to recognise an impairment charge of US$123 million. This was based on a fair value less cost of disposal (FVLCD) model, against property, plant and equipment and acquired software. Subsequently, Hydro withdrew its offer. We continue to actively market this CGU and have not identified any indications of further impairment or impairment reversals. Energy & Minerals – Rössing, Namibia In 2017, our annual impairment trigger assessment at the Rössing Uranium CGU identified a drop in forecast prices for uranium due to oversupply in the market. When we assessed the recoverable amount of the assets, we determined that the property, plant and equipment and certain other non-current assets should be fully impaired In 2018, we agreed to sell our share of Rössing Uranium to China National Uranium Corporation Limited. Subject to the completion of certain conditions precedent, the transaction is expected to complete in the first half of 2019. After taking account of the cash held by Rössing that will go to the buyer as part of the transaction, it is our expectation that the transaction will result in a cash outflow (refer to note 19). We have recognised a pre-tax impairment charge of US$9 million on transfer to assets held for sale to write off the property, plant and equipment purchased during the year. Copper & Diamonds – Argyle Diamond Mine, Australia In 2016, our annual impairment trigger assessment at the Argyle CGU identified the impact of lower production volumes compared with forecast and lower prices achieved for bulk diamonds as impairment indicators. We calculated a recoverable amount for Argyle of US$191 million, resulting in a pre-tax impairment charge of US$241 million to property, plant and equipment and intangible assets. In 2017, our annual impairment trigger assessment at the Argyle CGU identified impairment indicators because of lower production volumes compared with forecast, a smaller than expected contribution from productivity improvements and lower realised prices. In assessing the recoverable amount of the assets, we determined that the property, plant and equipment, including an updated closure asset, was fully impaired resulting in a pre-tax impairment charge of US$172 million. The impairment charge resulted in the recognition of deferred tax assets of US$34 million, which will be recovered by other business units in the same tax group. Energy & Minerals – Roughrider, Canada In 2017, after reassessing our planned exploration spend, we decided not to plan or budget for evaluating the Roughrider deposit. We identified this as an impairment indicator under IFRS 6 and, due to uncertainty around whether there are viable quantities of uranium there, set a recoverable amount of US$nil for the evaluation and exploration assets. In light of this, we recorded an impairment charge of US$357 million to write off the mineral interests recognised when we acquired Roughrider. Copper & Diamonds – Oyu Tolgoi, Mongolia As noted in the Strategic Report for Copper & Diamonds, the Group has observed a deterioration in some internal and external indicators of value for the Oyu Tolgoi CGU and has therefore prepared an assessment of recoverable amount. The net present value of post-tax cash flows, based on the IAS 36 fair value less costs of disposal (FVLCD) methodology, for the Oyu Tolgoi CGU, discounted at 8% in real-terms, exceeds the carrying value by US$3.1 billion. As such, no impairment charge has been recognised. The recoverable amount incorporates a reduction in value of approximately US$1.1 billion, compared with the 2017 forecast, as a result of those changes to the project schedule, cost and scope, including the location of the power station, where the extent of those changes, and their value impacts, can be reasonably assessed at this time. This reduction was offset by value accretion of US$1.3 billion due to the annual unwind of the discount for the timing of expected cash inflows and inflation. The individual assumptions subject to the most estimation uncertainty for the FVLCD calculation are the copper price and the discount rate. To illustrate these sensitivities, the valuation headroom would be eliminated by an increase to the discount rate of 1.9%, or a reduction of US$0.39 per pound to the forecast copper price throughout the life of the mine, if all other inputs remained constant. In the long term, this price sensitivity is the equivalent to a 13% reduction in copper prices. These cash flows have been calculated in line with the accounting policy set out in note 1(i) of the 2017 Annual Report. As set out in the Strategic report, in October 2018 we announced our annual reforecast of the development schedule which at that time suggested a nine-month delay in the schedule to sustainable production, primarily caused by delays in completing and equipping the primary production shaft and by some zones of variable rock strength that had been encountered. In December 2018, we announced the signing of the Power Source Framework Agreement, which sets out an amended timetable for Oyu Tolgoi to meet its obligation to source power domestically. These updates, together with an estimate of the financial impact of a potential further delay in the commissioning of the primary production shaft, have been reflected in the recoverable amount of the CGU as set out above. Since then, our mine design teams have continued to work with the more comprehensive geotechnical data that has become available as the underground development continues, and it is clear that potentially significant changes to the design of some future elements of the development, and to the development schedule, will be needed, to allow for zones of particularly variable rock strength which have been encountered in the footprint of the mine. The detailed design work is under way, as is the work Recognising the uncertainties noted above, as well as the time remaining through to ramp-up of commercial production, the Group highlights that it does not consider the current headroom to be indicative of an impairment reversal at this time.

Share of profit after tax of eq

Share of profit after tax of equity accounted units	12 Months Ended
	Dec. 31, 2018
Share Of Profit After Tax Of Equity Accounted Units [Abstract]
Share of profit after tax of equity accounted units	2018 2017 2016 US$m US$m US$m Sales revenue: Rio Tinto share (a) 2,497 1,960 1,727 Operating costs (1,656 ) (1,400 ) (1,237 ) Profit before finance items and taxation 841 560 490 Finance items (69 ) (47 ) (33 ) Share of profit after tax of equity accounted units 14 17 20 Profit before taxation 786 530 477 Taxation (273 ) (191 ) (156 ) Profit for the year (Rio Tinto share) 513 339 321 (a) Sales revenue of equity accounted units includes sales by equity accounted units to Group subsidiaries. Further information relating to the Group’s interests in joint ventures and associates is given in notes 35 and 36.

Finance income and finance cost

Finance income and finance costs	12 Months Ended
	Dec. 31, 2018
Disclosure Of Finance Income And Finance Costs [Abstract]
Finance income and finance costs	2018 2017 2016 Note US$m US$m US$m Finance income from equity accounted units (Rio Tinto share) 7 4 6 Other finance income (including bank deposits and other financial assets) 242 137 83 Total finance income 249 141 89 Interest on: – Financial liabilities at amortised cost and associated derivatives (775 ) (819 ) (895 ) – Finance leases (2 ) (3 ) (3 ) Fair value movements: – Bonds designated as hedged items in fair value hedges 96 28 89 – Derivatives designated as hedging instruments in fair value hedges (73 ) (22 ) (89 ) Loss on early redemption of bonds (a) (94 ) (256 ) (324 ) Amounts capitalised 14 296 224 111 Total finance costs (552 ) (848 ) (1,111 ) (a) In 2018, loss on early redemption of bonds includes a premium charge of US$72 million; unamortised debt issuance costs and fees of US$9 million, the write-off of the fair value hedge adjustment of US$16 million and the reclassification of a gain out of the cost of hedging reserve of US$3 million (see note 30). In 2017, loss on early redemption of bonds included a premium charge of US$238 million; unamortised debt issuance costs and fees of US$14 million and the write-off of the fair value hedge adjustment of US$4 million (see note 30). In 2016, loss of early redemption of bonds included a premium charge of US$441 million; unamortised debt issuance costs and fees of US$42 million partially offset by the write-off of fair value hedge adjustments of US$159 million (see note 30).

Taxation

Taxation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Income Tax [Abstract]
Taxation	2018 2017 2016 Note US$m US$m US$m Taxation charge – Current 3,726 3,270 2,115 – Deferred 17 516 695 (548 ) Total taxation charge 4,242 3,965 1,567 2018 2017 2016 Prima facie tax reconciliation US$m US$m US$m Profit before taxation 18,167 12,816 6,343 Deduct: share of profit after tax of equity accounted units (513 ) (339 ) (321 ) Parent companies' and subsidiaries' profit before tax 17,654 12,477 6,022 Prima facie tax payable at UK rate of 19% (2017: 19%; 2016: 20%) 3,354 2,371 1,204 Higher rate of taxation on Australian underlying earnings 1,106 1,069 604 Impact of items excluded in arriving at underlying earnings (a) – Impairment charges - 10 (16 ) – Net gains and losses on consolidation and disposal of interests in businesses (251 ) (123 ) 30 – Exchange and gains/(losses) on derivatives 32 (48 ) (33 ) – Losses from increases to closure estimates (non-operating and fully impaired sites) 30 - (40 ) – Gain relating to surplus land at Kitimat (81 ) - - – Changes in corporate tax rates in the US and France (b) - 439 - – Onerous port and rail contracts - - (46 ) – Tax provision (c) - - 380 – Tax charge relating to expected divestments (d) - 202 - – Other exclusions - 14 (48 ) Impact of changes in tax rates and laws 47 21 (9 ) Other tax rates applicable outside the UK and Australia on underlying earnings (47 ) (92 ) (283 ) Resource depletion and other depreciation allowances (46 ) (33 ) (15 ) Recognition of previously unrecognised deferred tax assets - (40 ) (154 ) Write-down of previously recognised deferred tax assets (e) 13 160 - Other items (f) 85 15 (7 ) Total taxation charge (g) 4,242 3,965 1,567 (a) The impact for each item includes the effect of tax rates applicable outside the UK. (b) In 2017, deferred tax assets were remeasured to reflect lower corporate income tax rates in the US and France as a result of tax legislation changes substantively enacted in December 2017. (c) Tax provision includes amounts provided for specific tax matters for which the timing of resolution and potential economic outflow are uncertain. During 2016, provision was made in relation to matters under discussion with the Australian Taxation Office (ATO) in relation to the transfer pricing of certain transactions between Rio Tinto entities based in Australia and the Group’s commercial centre in Singapore for the period since 2009. (d) In 2017, deferred tax assets were derecognised as a result of revised profit forecasts in France due to expected divestments of Dunkerque and ISAL. The Dunkerque divestment completed in 2018. (e) The write-down of previously recognised deferred tax assets in 2017 primarily relates to a reduction in recognised deferred tax assets on brought forward losses in Grasberg. (f) Other items include various adjustments to provisions for taxation of prior periods. (g) This tax reconciliation relates to the Group’s parent companies, subsidiaries and joint operations. The Group’s share of profit of equity accounted units is net of tax charges of US$273 million (2017: US$191 million; 2016: US$156 million). 2018 2017 2016 Total Total Total US$m US$m US$m Tax on fair value movements: – Cash flow hedge fair value (gains)/losses (54 ) (1 ) 4 Tax (charge)/credit on actuarial gains and losses on post-retirement benefit plans (271 ) (12 ) 29 Adjustments to deferred tax on post-retirement benefit plans due to changes in corporate tax rates in the US and France - (140 ) - Tax relating to components of other comprehensive income/(loss) for the year (a) (325 ) (153 ) 33 (a) This comprises a deferred tax charge of US$325 million (2017: charge of US$153 million; 2016: credit of US$33 million) and a current tax charge of US$nil (2017: US$nil; 2016: US$nil), plus a share of tax on other comprehensive income of equity accounted units shown separately (see note 17).

Earnings per ordinary share

Earnings per ordinary share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings per ordinary share	2018 2017 Weighted Weighted average 2018 average 2017 2018 number of Per share 2017 number of Per share Earnings shares amount Earnings shares amount US$m (millions) (cents) US$m (millions) (cents) Basic earnings per share attributable to ordinary shareholders of Rio Tinto (a) 13,638 1,719.3 793.2 8,762 1,786.7 490.4 Diluted earnings per share attributable to ordinary shareholders of Rio Tinto (b) 13,638 1,731.7 787.6 8,762 1,799.5 486.9 2016 Weighted average 2016 2016 number of Per share Earnings shares amount US$m (millions) (cents) Basic earnings per share attributable to ordinary shareholders of Rio Tinto (a) 4,617 1,797.3 256.9 Diluted earnings per share attributable to ordinary shareholders of Rio Tinto (b) 4,617 1,808.6 255.3 (a) The weighted average number of shares is calculated as the average number of Rio Tinto plc shares outstanding not held as treasury shares of 1,312.7 million (2017: 1,364.5 million; 2016: 1,373.7 million) plus the average number of Rio Tinto Limited shares outstanding of 406.6 million (2017: 422.3 million; 2016: 423.6 million) over the relevant period. No Rio Tinto Limited ordinary shares were held by Rio Tinto plc in any of the periods presented. (b) For the purposes of calculating diluted earnings per share, the effect of dilutive securities of 12.4 million shares in 2018 (2017: 12.8 million; 2016: 11.3 million) is added to the weighted average number of shares described in (a) above. This effect is calculated under the treasury stock method. In accordance with IAS 33 “Earnings per share”. The Group’s only potential dilutive ordinary shares are share options for which terms and conditions are described in note 43.

Dividends

Dividends	12 Months Ended
	Dec. 31, 2018
Disclosure Of Dividends [Abstract]
Dividends	2018 2017 2016 US$m US$m US$m Rio Tinto plc previous year final dividend paid 2,446 1,725 1,443 Rio Tinto plc interim dividend paid 1,666 1,530 604 Rio Tinto Limited previous year final dividend paid 731 523 473 Rio Tinto Limited interim dividend paid 513 472 205 Dividends paid during the year 5,356 4,250 2,725 Dividends per share: paid during the year 307.0 c 235.0 c 152.5 c Final dividends per share: proposed in the announcement of the results for the year 180.0c 180.0 c 125.0 c Special dividends per share: proposed in the announcement of the results for the year 243.0c - - Dividends Dividends Dividends per share per share per share 2018 2017 2016 Rio Tinto plc previous year final (pence) 129.43 p 100.56 p 74.21 p Rio Tinto plc interim (pence) 96.82 p 83.13 p 33.80 p Rio Tinto Limited previous year final – fully franked at 30% (Australian cents) 228.53 c 163.62 c 151.89 c Rio Tinto Limited interim – fully franked at 30% (Australian cents) 170.84 c 137.72 c 59.13 c Number Number Number of shares of shares of shares 2018 2017 2016 (millions) (millions) (millions) Rio Tinto plc previous year final 1,334.8 1,374.6 1,373.9 Rio Tinto plc interim 1,308.4 1,366.1 1,374.4 Rio Tinto Limited previous year final 412.4 424.0 423.5 Rio Tinto Limited interim 412.4 424.0 424.0 The dividends paid in 2018 are based on the following US cents per share amounts: 2017 final – 180.0 cents, 2018 interim – 127.0 cents (2017 dividends paid: 2016 final – 125.0 cents, 2017 interim – 110.0 cents; 2016 dividends paid: 2015 final – 107.5 cents, 2016 interim – 45.0 cents). The number of shares on which Rio Tinto plc dividends are based excludes those held as treasury shares and those held by employee share trusts which waived the right to dividends. Employee share trusts waived dividends on 132,294 Rio Tinto plc ordinary shares and 22,824 American Depository Receipts (ADRs) for the 2017 final dividend and on 314,529 Rio Tinto plc ordinary shares and 36,321 ADRs for the 2018 interim dividend (2017: 277,946 Rio Tinto plc ordinary shares and 22,021 ADRs for the 2016 final dividend and on 173,297 Rio Tinto plc ordinary shares and 24,377 ADRs for the 2017 interim dividend; 2016: 428,529 Rio Tinto plc ordinary shares and 13,881 ADRs for the 2015 final dividend and on 217,661 Rio Tinto plc ordinary shares and 31,604 ADRs for the 2016 interim dividend). In 2018, 2017 and 2016, no Rio Tinto Limited shares were held by Rio Tinto plc. Notes to the 2018 financial statements continued 11 Dividends continued The number of shares on which Rio Tinto Limited dividends are based excludes those held by shareholders who have waived the rights to dividends. Employee share trusts waived dividends on 130,129 Rio Tinto Limited ordinary shares for the 2017 final dividend and on 251,394 shares for the 2018 interim dividend (2017: 214,278 shares for the 2016 final dividend and on 274,899 shares for the 2017 interim dividend; 2016: 681,818 shares for the 2015 final dividend and on 152,834 shares for the 2016 interim dividend). In addition, the directors of Rio Tinto announced a final dividend of 180.0 cents per share and a special dividend of 243.0 cents per share on 27 February 2019. These are expected to result in payments of approximately US$7 billion. The dividends will be paid on 18 April 2019 to Rio Tinto plc and Rio Tinto Limited shareholders on the register at the close of business on 8 March 2019. The proposed Rio Tinto Limited dividends will be franked out of existing franking credits or out of franking credits arising from the payment of income tax during 2019. The approximate amount of the Rio Tinto Limited consolidated tax group’s retained profits and reserves that could be distributed as dividends and franked out of available credits that arose from net payments of income tax in respect of periods up to 31 December 2018 (after deducting franking credits expected to be utilised on the 2018 final dividend declared) is US$6,178 million (2017: US$8,542 million; 2016: US$11,577 million).

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2018
Goodwill [Abstract]
Goodwill	2018 2017 US$m US$m Net book value At 1 January 1,037 951 Adjustment on currency translation (125 ) 86 At 31 December 912 1,037 – cost 15,861 17,942 – accumulated impairment (14,949 ) (16,905 ) At 1 January – cost 17,942 17,144 – accumulated impairment (16,905 ) (16,193 ) At 31 December, goodwill has been allocated as follows: 2018 2017 US$m US$m Net book value Richards Bay Minerals 474 552 Pilbara 351 389 Dampier Salt 87 96 912 1,037 Impairment tests for goodwill Richards Bay Minerals Richards Bay Minerals’ annual impairment review resulted in no impairment charge for 2018 (2017: no impairment charge). The recoverable amount has been assessed by reference to FVLCD, in line with the policy set out in note 1(i) and classified as level 3 under the fair value hierarchy. FVLCD was determined by estimating cash flows until the end of the life-of-mine plan including anticipated expansions. In arriving at FVLCD, a post-tax discount rate of 8.8% (2017: 8.7%) has been applied to the post-tax cash flows expressed in real terms. The key assumptions to which the calculation of FVLCD for Richards Bay Minerals is most sensitive and the corresponding decrease in FVLCD are set out below: US$m 5% decrease in the titanium slag price 174 1% increase in the discount rate applied to post-tax cash flows 195 10% strengthening of the South African rand 328 Other assumptions include the long-term pig iron and zircon prices and operating costs. Future selling prices and operating costs have been estimated in line with the policy set out in note 1(i). The recoverable amount of the CGU exceeds the carrying value when each of these sensitivities are applied whilst keeping all other assumptions constant. Pilbara The annual impairment review of the Pilbara CGU has been assessed by reference to FVLCD using discounted cash flows, which is in line with the policy set out in note 1(i) and is classified as level 3 under the fair value hierarchy. In arriving at FVLCD, a post-tax discount rate of 6.8% (2017: 6.7%) has been applied to the post-tax cash flows expressed in real terms. The recoverable amount was determined to be significantly in excess of carrying value, and there are no reasonably possible changes in key assumptions that would cause the remaining goodwill to be impaired.

Intangible assets

Intangible assets	12 Months Ended
	Dec. 31, 2018
Intangible Assets [Abstract]
Intangible assets	Trademarks, Contract- Exploration patented and based Other and non-patented intangible intangible evaluation (a) technology assets (b) assets Total Year ended 31 December 2018 US$m US$m US$m US$m US$m Net book value At 1 January 2018 393 75 2,188 463 3,119 Adjustment on currency translation (25 ) (3 ) (171 ) (46 ) (245 ) Expenditure during the year 90 1 - 83 174 Amortisation for the year (c) - (14 ) (23 ) (96 ) (133 ) Impairment charges (d) - - - (2 ) (2 ) Disposals, transfers and other movements (e) (225 ) - (12 ) 103 (134 ) At 31 December 2018 233 59 1,982 505 2,779 – cost 2,346 217 3,114 1,538 7,215 – accumulated amortisation and impairment (2,113 ) (158 ) (1,132 ) (1,033 ) (4,436 ) Trademarks, Contract- Exploration patented and based Other and non-patented intangible intangible evaluation (a) technology assets (b) assets Total Year ended 31 December 2017 US$m US$m US$m US$m US$m Net book value At 1 January 2017 711 78 2,103 387 3,279 Adjustment on currency translation 27 10 150 29 216 Expenditure during the year 57 - - 65 122 Amortisation for the year (c) - (13 ) (67 ) (97 ) (177 ) Impairment charges (d) (357 ) - - - (357 ) Disposals, transfers and other movements (e) (45 ) - 2 79 36 At 31 December 2017 393 75 2,188 463 3,119 – cost 2,658 224 3,438 1,537 7,857 – accumulated amortisation and impairment (2,265 ) (149 ) (1,250 ) (1,074 ) (4,738 ) (a) Exploration and evaluation assets’ useful lives are not determined until transferred to property, plant and equipment. (b) The Group benefits from certain intangible assets acquired with Alcan, including power supply contracts, customer contracts and water rights. The water rights are expected to contribute to the efficiency and cost-effectiveness of operations for the foreseeable future: accordingly, these rights are considered to have indefinite lives and are not subject to amortisation but are tested annually for impairment. These water rights constitute the majority of the amounts in “Contract-based intangible assets”. The remaining carrying value of the water rights (US$1,684 million) as at 31 December 2018 relates wholly to the Quebec smelters CGU. The Quebec smelters CGU was tested for impairment by reference to FVLCD using discounted cash flows, which is in line with the policy set out in note 1(i). The recoverable amount of the Quebec smelters is classified as level 3 under the fair value hierarchy. In arriving at FVLCD, post-tax cash flows expressed in real terms have been estimated over the expected useful economic lives of the underlying smelting assets and discounted using a real post-tax discount rate of 6.8% (2017: 6.7%). The recoverable amounts were determined to be significantly in excess of carrying value, and there are no reasonably possible changes in key assumptions that would cause the remaining water rights to be impaired. (c) Finite life intangible assets are amortised over their useful economic lives on a straight line or units of production basis, as appropriate. Where amortisation is calculated on a straight line basis, the following useful lives have been determined: Trademarks, patented and non-patented technology Trademarks: 14 to 20 years Patented and non-patented technology: ten to 20 years Contract-based intangible assets Power contracts/water rights: two to 45 years Other purchase and customer contracts: five to 15 years Other intangible assets Internally generated intangible assets and computer software: two to five years Other intangible assets: two to 20 years (d) Impairment charges in 2018 relate to the ISAL Smelter (see note 6). Impairment charges in 2017 relate to the full write-off of the Roughrider deposit in Canada (see note 6). (e) Disposals, transfers and other movements includes transfers to assets held for sale relating to Rössing Uranium and ISAL assets, transfers to Mining properties and leases in relation to the Koodaideri mine from Exploration and evaluation, offset by transfers into other intangibles as part of the Autohaul project. Disposals, transfers and other movements for Exploration and evaluation in 2017 included US$34 million transferred to Mining Property in relation to the Kemano tunnel following approval of the project. Notes to the 2018 financial statements continued 13 Intangible assets continued Exploration and evaluation expenditure The charge for the year and the net amount of intangible assets capitalised during the year are as follows: 2018 2017 2016 US$m US$m US$m Net expenditure in the year (net of cash proceeds of US$233 million (2017: US$3 million; 2016: US$208 million) on disposal of undeveloped projects) (345 ) (493 ) (284 ) Non-cash movements and non-cash proceeds on disposal of undeveloped projects 45 (24 ) (177 ) Amount capitalised during the year 90 57 8 Net charge for the year (210 ) (460 ) (453 ) Reconciliation to income statement Exploration and evaluation costs (488 ) (445 ) (497 ) Profit/(loss) relating to interests in undeveloped projects (a) 278 (15 ) 44 Net charge for the year (210 ) (460 ) (453 ) (a) During 2018, profit relating to interests in undeveloped properties relates to the gains on the sales of Valeria (US$83 million) and Winchester South (US$195 million) undeveloped properties which are included within underlying earnings. At 31 December 2018, a total of US$233 million had been capitalised related to projects which had not yet been approved to proceed (31 December 2017: a total of US$420 million had been capitalised comprising: evaluation costs of US$393 million included above and US$27 million of early works expenditure within property, plant and equipment).

Property, plant and equipment

Property, plant and equipment	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Property, plant and equipment	Mining Land Plant Capital properties and and works in and leases (a) buildings (b) equipment progress Total Year ended 31 December 2018 Note US$m US$m US$m US$m US$m Net book value At 1 January 2018 11,488 7,376 36,285 6,944 62,093 Adjustment on currency translation (c) (689 ) (548 ) (2,671 ) (249 ) (4,157 ) Adjustments to capitalised closure costs 26 486 - - - 486 Interest capitalised (d) 8 - - - 296 296 Additions 403 80 459 4,359 5,301 Depreciation for the year (a) (e) (664 ) (382 ) (2,836 ) - (3,882 ) Impairment charges (f) (3 ) (20 ) (101 ) (6 ) (130 ) Disposals (1 ) (54 ) (71 ) (4 ) (130 ) Subsidiaries no longer consolidated (g) (1,103 ) (377 ) (1,392 ) (514 ) (3,386 ) Transfers and other movements (h) 1,146 188 2,346 (3,810 ) (130 ) At 31 December 2018 11,063 6,263 32,019 7,016 56,361 – cost 23,318 10,601 63,051 7,324 104,294 – accumulated depreciation and impairment (12,255 ) (4,338 ) (31,032 ) (308 ) (47,933 ) Non-current assets held under finance leases (i) - - 31 - 31 Non-current assets pledged as security (j) 3,054 385 5,194 4,588 13,221 Mining Land Plant Capital properties and and works in and leases (a) buildings (b) equipment progress Total Year ended 31 December 2017 Note US$m US$m US$m US$m US$m Net book value At 1 January 2017 10,848 7,316 35,706 4,985 58,855 Adjustment on currency translation (c) 495 461 2,242 183 3,381 Adjustments to capitalised closure costs 26 710 - - - 710 Interest capitalised (d) 8 - - - 224 224 Additions 230 41 646 3,834 4,751 Depreciation for the year (a) (e) (673 ) (403 ) (3,122 ) - (4,198 ) Impairment charges (f) (304 ) (2 ) (128 ) (1 ) (435 ) Disposals - (57 ) (40 ) (26 ) (123 ) Subsidiaries no longer consolidated (g) (211 ) (95 ) (417 ) (26 ) (749 ) Transfers and other movements (h) 393 115 1,398 (2,229 ) (323 ) At 31 December 2017 11,488 7,376 36,285 6,944 62,093 – cost 24,691 12,029 71,903 7,266 115,889 – accumulated depreciation and impairment (13,203 ) (4,653 ) (35,618 ) (322 ) (53,796 ) Non-current assets held under finance leases (i) - - 37 - 37 Non-current assets pledged as security (j) 3,307 410 5,308 3,278 12,303 (a) At 31 December 2018, the net book value of capitalised production phase stripping costs totalled US$2,050 million, with US$1,572 million within Property, plant and equipment and a further US$478 million within Investments in equity accounted units (2017: total of US$1,815 million with US$1,374 million in Property, plant and equipment and a further US$441 million within Investments in equity accounted units). During the year capitalisation of US$526 million was partly offset by depreciation of US$274 million (including amounts recorded within equity accounted units). Depreciation of deferred stripping costs in respect of subsidiaries of US$134 million (2017: US$194 million; 2016: US$203 million) is included within “Depreciation for the year”. (b) At 31 December 2018, the net book value amount for land and buildings includes freehold US$6,240 million (2017: US$7,294 million) and long leasehold US$23 million (2017: US$82 million). (c) Adjustment on currency translation represents the impact of exchange differences arising on the translation of the assets of entities with functional currencies other than the US dollar, recognised directly in the currency translation reserve. The adjustment in 2018 arose from the strengthening of the US dollar against other currencies. (d) Interest is capitalised at a rate based on the Group or relevant subsidiary’s cost of borrowing or at the rate on project specific debt, where applicable. The Group’s average borrowing rate used for capitalisation of interest is 4.90% (2017: 4.45%). (e) Assets within operations for which production is not expected to fluctuate significantly from one year to another or which have a physical life shorter than the related mine are depreciated on a straight line basis as follows: Land and buildings Land: not depreciated Buildings: five to 50 years Plant and equipment Other plant and equipment: three to 50 years Power assets: 25 to 50 years Capital work in progress: not depreciated (f) During 2018, impairment charges primarily related to the ISAL Smelter (see note 6). During 2017, impairment charges primarily related to Argyle Diamonds and Rössing Uranium (see note 6). (g) During 2018, “Subsidiaries no longer consolidated” relates primarily to the disposal of Kestrel and Hail Creek, which completed on 1 August 2018 and the disposal of Grasberg on 21 December 2018. Refer to note 37. During 2017, “Subsidiaries no longer consolidated” relates primarily to the disposal of Coal & Allied Industries Limited, which completed on 1 September 2017. (h) “Transfers and other movements” includes reclassifications between categories and transfers to assets held for sale relating to Rössing Uranium and ISAL assets in 2018, and Dunkerque in 2017. (i) The finance leases under which these assets are held are disclosed in note 23. (j) Excludes assets held under finance leases. Non-current assets pledged as security represent amounts pledged as collateral against US$4,562 million (2017: US$4,677 million) of loans, which are included in note 22.

Investments in equity accounted

Investments in equity accounted units	12 Months Ended
	Dec. 31, 2018
Disclosure Of Investments Accounted For Using Equity Method Explanatory [Abstract]
Investments in equity accounted units	2018 2017 Summary balance sheet (Rio Tinto share) US$m US$m Rio Tinto's share of assets – Non-current assets 6,000 5,913 – Current assets 887 990 6,887 6,903 Rio Tinto's share of liabilities – Current liabilities (607 ) (654 ) – Non-current liabilities (1,981 ) (1,763 ) (2,588 ) (2,417 ) Rio Tinto's share of net assets 4,299 4,486 Further details of investments in equity accounted units are set out in notes 35 and 36. At 31 December 2018 and 2017, the Group had no investments in equity accounted units with shares listed on recognised stock exchanges. At 31 December 2018, net debt of equity accounted units, excluding amounts due to Rio Tinto, was US$1,158 million (2017: US$1,244 million).

Inventories

Inventories	12 Months Ended
	Dec. 31, 2018
Disclosure Of Inventories [Abstract]
Inventories	Notes to the 2018 financial statements continued 2018 2017 US$m US$m Raw materials and purchased components 734 648 Consumable stores 862 875 Work in progress 1,026 1,082 Finished goods and goods for resale 977 1,027 Total inventories 3,599 3,632 Comprising: Expected to be used within one year 3,447 3,472 Expected to be used after more than one year 152 160 Total inventories 3,599 3,632 During 2018, the Group recognised inventory write-downs, net of reversals, amounting to US$48 million. During 2017, the Group recognised a net inventory write-back of US$7 million. This comprised a US$81 million write-back of amounts previously written down due to an increase in realisable values, partly offset by inventory write-offs of US$74 million. At 31 December 2018, US$566 million (2017: US$611 million) of inventories were pledged as security for liabilities.

Deferred taxation

Deferred taxation	12 Months Ended
	Dec. 31, 2018
Deferred Tax Assets And Liabilities [Abstract]
Deferred taxation	2018 2017 US$m US$m At 1 January – 233 (607 ) Adjustment to opening balance on transition to IFRS 15 (71 ) - At 1 January – restated opening balance 162 (607 ) Adjustment on currency translation (172 ) 53 Charged to the income statement 516 695 Charged to statement of comprehensive income (a) 325 153 Disposals (263 ) - Other movements (b) (32 ) (61 ) At 31 December – 536 233 Comprising: – deferred tax liabilities (c) (d) 3,673 3,628 – deferred tax assets (c) (e) (f) (3,137 ) (3,395 ) Deferred tax balances for which there is a right of offset within the same tax jurisdiction are presented net on the face of the balance sheet as permitted by IAS 12. The closing deferred tax liabilities and assets, prior to this offsetting of balances, are shown below. Total Total 2018 2017 US$m US$m Deferred tax liabilities arising from: Capital allowances 4,408 5,208 Unremitted earnings (d) 454 588 Capitalised interest 259 391 Unrealised exchange gains 5 31 Other temporary differences 309 222 Total 5,435 6,440 Deferred tax assets arising from: Tax losses (e) (1,894 ) (2,282 ) Provisions (1,585 ) (1,731 ) Capital allowances (154 ) (579 ) Post-retirement benefits (293 ) (616 ) Unrealised exchange losses (187 ) (317 ) Other temporary differences (786 ) (682 ) Total (4,899 ) (6,207 ) Charged/(credited) to the income statement Unrealised exchange losses 57 36 Tax losses (30 ) 12 Provisions (19 ) 451 Capital allowances 461 278 Tax on unremitted earnings (33 ) 4 Post-retirement benefits 30 149 Other temporary differences 50 (235 ) Total 516 695 (a) The amounts charged directly to the Statement of comprehensive income include provisions for tax on exchange differences on intragroup loans qualifying for reporting as part of the net investment in subsidiaries, on cash flow hedges and on actuarial gains and losses on pension schemes and on post-retirement healthcare plans. (b) “Other movements” include deferred tax relating to tax payable recognised by subsidiary holding companies on the profits of the equity accounted units to which it relates. (c) The deferred tax liability of US$3,673 million (2017: US$3,628 million) includes US$3,658 million (2017: US$3,615 million) due in more than one year. The deferred tax asset of US$3,137 million (2017: US$3,395 million) includes US$3,133 million (2017: US$3,386 million) receivable in more than one year. All amounts are shown as non-current on the face of the balance sheet as required by IAS 12. (d) Deferred tax is not recognised on the unremitted earnings of subsidiaries and joint ventures totalling US$3,726 million (2017: US$3,242 million) where the Group is able to control the timing of the remittance and it is probable that there will be no remittance in the foreseeable future. If these earnings were remitted, tax of US$157 million (2017: US$131 million) would be payable. (e) There is a limited time period, the shortest of which is six years, for the recovery of US$1,519 million (2017: US$1,679 million) of tax losses and other tax assets which have been recognised as deferred tax assets in the financial statements. (f) Recognised and unrecognised deferred tax assets are shown in the table below and totalled US$5,647 million at 31 December 2018 (2017: US$7,071 million). Of this total, US$3,137 million has been recognised as deferred tax assets (2017: US$3,395 million), leaving US$2,510 million (2017: US$3,676 million) unrecognised, as recovery is not considered probable. The recognised amounts do not include deferred tax assets that have been netted off against deferred tax liabilities. Recognised Unrecognised 2018 2017 2018 2017 At 31 December US$m US$m US$m US$m France - - 1,122 1,163 Canada 545 546 559 674 US 932 877 12 7 Australia 796 1,055 289 257 Mongolia (a) 703 631 87 61 Other (b) 161 286 441 1,514 Total 3,137 3,395 2,510 3,676 (a) Deferred tax assets in Mongolia include US$469 million (2017: US$432 million) from tax losses that expire if not recovered against taxable profits within eight years. Tax losses have been calculated in accordance with the provisions of the Oyu Tolgoi Investment Agreement and Mongolian laws. Recovery of the recognised deferred tax assets is expected to commence from 2024 based on projected cash flows in the latest life-of-mine plan, which has been calculated on a consistent basis with the impairment test described in note 6. Tax law in Mongolia and its interpretation by the tax authority has been, and is expected to continue to be, subject to change. Such future changes could have a material impact on the amount and period of recovery of these deferred tax assets. (b) US$684 million (2017: US$777 million) of the unrecognised assets relate to realised or unrealised capital losses, the recovery of which depends on the existence of capital gains in future years. There is a time limit, the shortest of which is one year, for the recovery of US$96 million of the unrecognised assets (2017: US$250 million).

Trade and other receivables

Trade and other receivables	12 Months Ended
	Dec. 31, 2018
Trade And Other Receivables [Abstract]
Trade and other receivables	Notes to the 2018 financial statements continued Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 US$m US$m US$m US$m US$m US$m Trade receivables (a) - 2,167 2,167 1 2,314 2,315 Other financial receivables (a) 240 550 790 178 462 640 Amounts due from equity accounted units - 50 50 - 30 30 Other receivables 129 226 355 348 358 706 Prepayment of tolling charges to jointly controlled entities (b) 228 - 228 269 - 269 Pension surpluses (note 44) 935 - 935 871 - 871 Other prepayments 53 186 239 57 279 336 Total 1,585 3,179 4,764 1,724 3,443 5,167 (a) At 31 December 2018, trade and other financial receivables are stated net of allowances for expected credit losses of US$8 million. The 2017 closing provision for doubtful debt under IAS 39 of US$55 million was adjusted by US$7 million (pre-tax) upon adoption of IFRS 9 (refer to note 45). During the year there has been an increase to the provision for expected credit losses of US$2 million and US$42 million has been utilised. (b) These prepayments will be charged to Group operating costs as processing takes place. There is no material element of trade and other receivables that is interest-bearing or financing in nature. The fair value of current trade and other receivables and the majority of amounts classified as non-current trade and other receivables approximates to their carrying value. There are no material trade receivables that are past due but not impaired.

Assets and liabilities held for

Assets and liabilities held for sale	12 Months Ended
	Dec. 31, 2018
Noncurrent Assets Or Disposal Groups Classified As Held For Sale Or As Held For Distribution To Owners [Abstract]
Assets and liabilities held for sale	At 31 December 2018, assets and liabilities held for sale include Rio Tinto’s interest in the Rössing Uranium mine (US$106 million) and the ISAL Smelter, the Aluchemie anode plant and the Alufluor aluminium fluoride plant (US$334 million). At 31 December 2017, assets and liabilities held for sale included Rio Tinto's interest in the Dunkerque aluminium smelter (US$355 million) and certain other separate assets. The major classes of assets and liabilities of those entities classified as held for sale at 31 December 2018 are: 2018 2017 US$m US$m Assets Intangible assets 4 6 Property, plant and equipment 238 190 Investments in equity accounted units 5 - Inventories 186 88 Deferred tax assets 66 49 Trade and other receivables 58 139 Other financial assets (including loans to equity accounted units) 60 22 Cash and cash equivalents 117 - Assets of disposal groups held for sale 734 494 Liabilities Trade and other payables (134) (60) Provisions including post-retirement benefits (160) (64) Liabilities of disposal groups held for sale (294) (124) Net assets associated with disposal groups 440 370 On completion of the sale of Rössing Uranium, it is expected that a loss of approximately US$300 million will be recognised, including the loss that will be recycled from the currency translation reserve on sale of the business. The loss is subject to currency movements up until completion of the sale, which is expected to be in the first half of 2019.

Other financial assets (includi

Other financial assets (including non-quasi equity loans to equity accounted units)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Other Financial Assets [Abstract]
Other financial assets (including non-quasi equity loans to equity accounted units)	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 US$m US$m US$m US$m US$m US$m Derivative financial instruments 468 88 556 238 29 267 Equity shares and quoted funds 53 77 130 45 91 136 Other investments, including loans (a) 255 2,527 2,782 188 964 1,152 Loans to equity accounted units 38 - 38 39 - 39 Total 814 2,692 3,506 510 1,084 1,594 (a) Current “Other investments, including loans” comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets held in managed investment funds classified as held for trading. Detailed information relating to other financial assets is given in note 30.

Cash and cash equivalents

Cash and cash equivalents	12 Months Ended
	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	2018 2017 Note US$m US$m Cash at bank and in hand 740 1,035 Money market funds and other cash equivalents 10,033 9,515 Balance per Group balance sheet 10,773 10,550 Bank overdrafts repayable on demand (unsecured) 22 (1 ) (3 ) Cash and cash equivalents included in Assets held for sale 19 117 - Balance per Group cash flow statement 10,889 10,547 Cash and cash equivalents of US$186 million (2017: US$290 million) are held in countries where there are restrictions on remittances. Of this balance, US$142 million (2017: US$158 million) could be used to repay subsidiaries’ third-party borrowings. There are also restrictions on a further US$1,090 million (2017: US$1,089 million) of cash and cash equivalents, the majority of which is held by partially owned subsidiaries and is not available for use in the wider Group due to legal and contractual restrictions currently in place. Of this balance US$864 million (2017: US$703 million) could be used to repay subsidiaries’ third-party borrowings.

Borrowings and other financial

Borrowings and other financial liabilities	12 Months Ended
	Dec. 31, 2018
Borrowings And Other Financial Liabilities [Abstract]
Borrowings and other financial liabilities	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 Borrowings at 31 December Note US$m US$m US$m US$m US$m US$m Rio Tinto Finance plc Euro Bonds 2.0% due 2020 (a) (b) 468 - 468 921 - 921 Rio Tinto Finance (USA) Limited Bonds 4.125% 2021 (a) - - - 428 - 428 Rio Tinto Finance (USA) Limited Bonds 3.750% 2021 (a) - - - 347 - 347 Rio Tinto Finance (USA) plc Bonds 3.5% 2022 (a) - - - 227 - 227 Rio Tinto Finance (USA) plc Bonds 2.875% 2022 (a) - - - 377 - 377 Rio Tinto Finance plc Euro Bonds 2.875% due 2024 (a) (b) 514 - 514 644 - 644 Rio Tinto Finance (USA) Limited Bonds 3.75% 2025 (a) 1,170 - 1,170 1,192 - 1,192 Rio Tinto Finance (USA) Limited Bonds 7.125% 2028 (a) 927 - 927 965 - 965 Alcan Inc. Debentures 7.25% due 2028 104 - 104 105 - 105 Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 (a) (b) 633 - 633 669 - 669 Alcan Inc. Debentures 7.25% due 2031 421 - 421 422 - 422 Alcan Inc. Global Notes 6.125% due 2033 741 - 741 740 - 740 Alcan Inc. Global Notes 5.75% due 2035 288 - 288 287 - 287 Rio Tinto Finance (USA) Limited Bonds 5.2% 2040 (a) 1,095 - 1,095 1,102 - 1,102 Rio Tinto Finance (USA) plc Bonds 4.75% 2042 (a) 462 - 462 467 - 467 Rio Tinto Finance (USA) plc Bonds 4.125% 2042 (a) 685 - 685 691 - 691 Oyu Tolgoi LLC MIGA Insured Loan LIBOR plus 2.65% due 2027 (c) 676 - 676 674 - 674 Oyu Tolgoi LLC Commercial Banks "B Loan" LIBOR plus 3.4% due 2027 (c) 1,588 - 1,588 1,588 - 1,588 Oyu Tolgoi LLC Export Credit Agencies Loan 2.3% due 2028 (c) 272 - 272 255 - 255 Oyu Tolgoi LLC Export Credit Agencies Loan LIBOR plus 3.65% due 2029 (c) 871 - 871 869 - 869 Oyu Tolgoi LLC International Financial Institutions "A Loan" LIBOR plus 3.78% due 2030 (c) 768 - 768 761 - 761 Loans from equity accounted units - - - - 31 31 Other secured loans 345 42 387 451 79 530 Other unsecured loans 373 264 637 393 435 828 Finance leases 23 39 5 44 49 4 53 Bank overdrafts 21 - 1 1 - 3 3 Total borrowings including overdrafts (d) 12,440 312 12,752 14,624 552 15,176 (a) These borrowings are subject to the hedging arrangements summarised below. Fair value hedge accounting has been applied except for the Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 which has cash flow hedge accounting applied. (b) Rio Tinto has a US$10 billion (2017: US$10 billion) European Debt Issuance Programme against which the cumulative amount utilised was US$1.6 billion equivalent at 31 December 2018 (2017: US$2.2 billion). The carrying value of these bonds after hedge accounting adjustments amounted to US$1.6 billion (2017: US$ 2.2 billion) in aggregate. (c) These borrowings relate to the Oyu Tolgoi LLC project finance facility. The project finance facility provides for interest-only payments for the first five years followed by minimum repayments according to a stepped amortisation schedule for the remaining life of the facility. The due dates stated represent the final repayment date. The interest rates stated are pre-completion and will increase by 1% post-completion. (d) The Group’s borrowings of US$12.8 billion (2017: US$15.2 billion) include US$2.4 billion (2017: US$2.7 billion) which relates to subsidiary entity borrowings that are without recourse to the Group, and US$4.6 billion (2017: US$4.7 billion) which is subject to various financial and general covenants with which the respective borrowers were in compliance as at 31 December 2018. Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 Other financial liabilities US$m US$m US$m US$m US$m US$m Derivative financial instruments 407 95 502 481 50 531 Other financial liabilities - 666 666 43 302 345 Total other financial liabilities 407 761 1,168 524 352 876 Total borrowings including overdrafts (as above) 12,440 312 12,752 14,624 552 15,176 Total borrowings and other financial liabilities 12,847 1,073 13,920 15,148 904 16,052 Swap arrangements At 31 December 2018, US$4.3 billion (2017: US$5.7 billion) US dollar notional of the fixed rate US dollar borrowings were swapped to floating US dollar rates and US$0.9 billion (2017: US$1.5 billion) US dollar notional equivalent of euro borrowings were fully swapped to floating US dollar rates. Hedge accounting has been applied to the full notional of items marked (a) in the above table except for: US$75 million (2017: US$75 million) of the Rio Tinto Finance (USA) Limited Bonds 7.125% due 2028. This portion is held at amortised cost. The Rio Tinto Finance plc Sterling Bond 4.0% due 2029 at US$0.6 billion (2017: US$0.7 billion) US dollar notional equivalent of sterling was fully swapped to US dollar notional and fixed US dollar rates. Cash flow hedging was applied to the annual interest coupons and principal of this bond. The hedge was fully effective in 2018 and 2017 financial years as the notional amount, maturity, payment and reset dates match. The fair value of interest rate and cross-currency interest rate swaps at 31 December 2018 was US$70 million (2017: US$99 million) asset and US$358 million (2017: US$276 million) liability, respectively. These are included within “Other financial assets” and “Other financial liabilities” in the balance sheet. The change in fair value used for measuring ineffectiveness for the period is shown in note 8. The main sources of ineffectiveness include changes in the timing of the cash flows of the hedging instrument compared to the underlying hedged item and changes in the credit risk of parties to the hedging relationship. Details of the major interest rate and cross-currency interest rate swaps are shown in note 30.

Capitalised finance leases

Capitalised finance leases	12 Months Ended
	Dec. 31, 2018
Disclosure Of Capitalised Finance Leases [Abstract]
Capitalised finance leases	2018 2017 Note US$m US$m Present value of minimum lease payments Total minimum lease payments 45 57 Effect of discounting (1 ) (4 ) Total 22 44 53 Payments under capitalised finance leases Due within 1 year 5 4 Between 1 and 3 years 10 14 Between 3 and 5 years 18 28 More than 5 years 12 11 Total 45 57

Consolidated net cash_(debt)

Consolidated net cash/(debt)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Consolidated Net Debt [Abstract]
Consolidated net cash/(debt)	Financing liabilities (b) Other assets Borrowings (including finance leases) excluding Debt-related derivatives (included in Other financial assets/ Cash/ Other Net overdrafts (a) liabilities) overdrafts (b) investments (c) (debt)/cash Year ended 31 December 2018 US$m US$m US$m US$m US$m Analysis of changes in consolidated net cash/(debt) Opening balance (15,173 ) (177 ) 10,547 958 (3,845 ) Foreign exchange adjustment 126 (64 ) 151 - 213 Cash movements excluding exchange movements 2,246 51 191 1,557 4,045 Other non-cash movements 50 (98 ) (117 ) 7 (158 ) Closing balance (12,751 ) (288 ) 10,772 2,522 255 Financing liabilities (b) Other assets Borrowings (including finance leases) excluding Debt-related derivatives (included in Other financial assets/ Cash/ Other Net overdrafts (a) liabilities) overdrafts (b) investments (c) debt Year ended 31 December 2017 US$m US$m US$m US$m US$m Analysis of changes in consolidated net debt Opening balance (17,618 ) (408 ) 8,189 250 (9,587 ) Foreign exchange adjustment (303 ) 245 (12 ) - (70 ) Cash movements excluding exchange movements 2,777 7 2,370 705 5,859 Other non-cash movements (29 ) (21 ) - 3 (47 ) Closing balance (15,173 ) (177 ) 10,547 958 (3,845 ) (a) Borrowings (including finance leases) at 31 December 2018 differ from total borrowings on the balance sheet as they exclude overdrafts of US$1 million (31 December 2017: US$3 million), other current financial liabilities of US$761 million (31 December 2017: US$352 million) and other non-current financial liabilities US$407 million (31 December 2017: US$524 million). (b) Closing cash/overdrafts at 31 December 2018 differ from cash and cash equivalents on the balance sheet as they include overdrafts of US$1 million which have been classified as a financial liability (31 December 2017: US$3 million). Other non-cash movements represents the reclassification of cash and cash equivalents in disposal groups to assets held for sale. (c) Other investments comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets held in managed investment funds classified as held for trading. Further information relating to the currency and interest rate exposures arising from net debt and related derivatives is given in note 30.

Trade and other payables

Trade and other payables	12 Months Ended
	Dec. 31, 2018
Trade And Other Payables [Abstract]
Trade and other payables	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 US$m US$m US$m US$m US$m US$m Trade payables - 3,180 3,180 - 3,255 3,255 Other financial payables 256 653 909 265 867 1,132 Other payables 165 114 279 87 97 184 Deferred income (a) 176 234 410 246 246 492 Accruals 11 1,229 1,240 13 1,347 1,360 Employee entitlements - 630 630 - 734 734 Royalties and mining taxes 1 487 488 4 492 496 Amounts owed to equity accounted units 156 67 223 156 19 175 Government grants deferred 76 6 82 85 4 89 Total 841 6,600 7,441 856 7,061 7,917 (a) Deferred income includes contract liabilities of US$198 million. The fair value of trade payables and financial instruments within other payables approximates their carrying value.

Provisions (including post-reti

Provisions (including post-retirement benefits)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Other Provisions [Abstract]
Provisions (including post-retirement benefits)	Pensions Close-down and Other and post-retirement employee restoration/ Total Total healthcare (a) entitlements (b) environmental (c) Other 2018 2017 Note US$m US$m US$m US$m US$m US$m At 1 January 3,370 389 9,983 900 14,642 13,794 Adjustment on currency translation (145 ) (37 ) (656 ) (60 ) (898 ) 846 Adjustments to mining properties: 14 – changes in estimate - - 486 - 486 710 Charged/(credited) to profit: – increases to existing and new provisions 267 185 456 229 1,137 797 – unused amounts reversed - (36 ) (38 ) (70 ) (144 ) (187 ) – exchange losses/(gains) on provisions - - 13 3 16 (83 ) – amortisation of discount - - 372 9 381 383 Utilised in year (219 ) (122 ) (319 ) (177 ) (837 ) (1,053 ) Actuarial (gains)/losses recognised in equity (781 ) - - - (781 ) 121 Subsidiaries no longer consolidated (d) - (29 ) (257 ) (32 ) (318 ) (622 ) Transfers and other movements (e) (6 ) 10 (65 ) (15 ) (76 ) (64 ) At 31 December 2,486 360 9,975 787 13,608 14,642 Balance sheet analysis: Current 79 274 476 227 1,056 1,275 Non-current 2,407 86 9,499 560 12,552 13,367 Total 2,486 360 9,975 787 13,608 14,642 (a) The main assumptions used to determine the provision for pensions and post-retirement healthcare, and other information, including the expected level of future funding payments in respect of those arrangements, are given in note 44. (b) The provision for other employee entitlements includes a provision for long service leave of US$242 million (2017: US$292 million), based on the relevant entitlements in certain Group operations and includes US$46 million (2017: US$24 million) of provision for redundancy and severance payments. (c) The Group’s policy on close-down and restoration costs is described in note 1(k) on page 159 and in paragraph (iv) under “Critical accounting policies and estimates” on pages 162 to 164. Close-down and restoration costs are a normal consequence of mining, and the majority of close-down and restoration expenditure is incurred in the years following closure of the mine, refinery or smelter. Remaining lives of operations and infrastructure range from one to over 60 years with an average for all sites, weighted by present closure obligation, of around 17 years (2017: 20 years). Although the ultimate cost to be incurred is uncertain, the Group’s businesses estimate their respective costs based on current restoration standards and techniques. Provisions of US$9,975 million (2017: US$9,983 million) for close-down and restoration costs and environmental clean-up obligations are based on risk-adjusted cash flows. These estimates have been discounted to their present value at a real risk-free rate of 2% per annum, based on an estimate of the long-term, risk-free, pre-tax cost of borrowing. If the risk-free rate was decreased by 0.5% then the provision would be US$1,139 million higher. Non-current provisions for close-down and restoration/environmental expenditure include amounts relating to environmental clean-up of US$535 million (2017: US$336 million) expected to take place between one and five years from the balance sheet date, and US$683 million (2017: US$839 million) expected to take place later than five years after the balance sheet date. Close-down and restoration/environmental liabilities at 31 December 2018 have not been adjusted for amounts of US$110 million (2017: US$75 million) arising from closure-related receivables from the co-owners of the Diavik Joint Venture and insurance recoveries and other financial assets held for the purposes of meeting these obligations. (d) “Subsidiaries no longer consolidated” relates primarily to the disposal of Kestrel and Hail Creek, which completed on 1 August 2018 and the disposal of Grasberg on 21 December 2018. In 2017 it related to the disposal of Coal & Allied Industries Limited, which completed on 1 September 2017. Refer to note 37. (e) Transfers and other movements include transfers to liabilities held for sale relating to Rössing Uranium and ISAL provisions. It also includes an adjustment to record Diavik Diamond Mines Inc. obligations for close-down and restoration on a 100% basis (previously 60% share). Refer to note 33 footnote (e).

Share capital - Rio Tinto plc

Share capital - Rio Tinto plc	12 Months Ended
	Dec. 31, 2018
Disclosure Of Classes Of Share Capital [Abstract]
Share capital - Rio Tinto plc	2018 2017 2016 Number Number Number 2018 2017 2016 (million) (million) (million) US$m US$m US$m Issued and fully paid up share capital of 10p each At 1 January 1,351.609 1,384.520 1,384.487 220 224 224 Ordinary shares issued (a) (c) 0.035 0.026 0.033 - - - Shares purchased and cancelled (b) (63.984 ) (32.937 ) - (9 ) (4 ) - At 31 December 1,287.660 1,351.609 1,384.520 211 220 224 Shares held by public At 1 January 1,342.058 1,374.822 1,374.046 Shares reissued from treasury (a) 0.106 0.147 0.743 Shares purchased and cancelled (b) (63.984 ) (32.937 ) - Ordinary shares issued (a) (c) 0.035 0.026 0.033 At 31 December 1,278.215 1,342.058 1,374.822 Shares held in treasury 9.445 9.551 9.698 Shares held by public 1,278.215 1,342.058 1,374.822 Total share capital 1,287.660 1,351.609 1,384.520 Other share classes Special Voting Share of 10p each (d) 1 only 1 only 1 only DLC Dividend Share of 10p each (d) 1 only 1 only 1 only Equalisation Share of 10p each (d) 1 only 1 only 1 only (a) 35,380 ordinary shares were issued in 2018 under the Global Employee Share Plan (GESP). 106,045 ordinary shares were reissued from treasury during the year resulting from the vesting of awards and the exercise of options under Rio Tinto plc employee share-based payment plans, with exercise prices and market values between £16.53 and £43.79 per share (2017: 26,241 ordinary shares were issued under the GESP and 147,126 ordinary shares were reissued from treasury with exercise prices and market values between £28.63 and £37.78 per share; 2016: 33,210 ordinary shares were issued under the GESP and 743,380 ordinary shares reissued from treasury with exercise prices and market values between £16.53 and £32.23 per share). (b) The authority for the company to buy-back its ordinary shares was renewed at the 2018 annual general meeting. 63,984,287 shares were bought back and cancelled in 2018 under the on-market buy-back programme. 32,937,109 shares were bought back and cancelled in 2017 under the on-market buy-back programme. No shares were bought back in 2016. (c) The aggregate consideration for new shares issued under the GESP was US$1.0 million (2017: US$1.0 million; 2016: US$0.9 million). The difference between the nominal value and the issue price of the shares issued was credited to the share premium account. The aggregate consideration received for treasury shares reissued was US (d) The “Special Voting Share” was issued to facilitate the joint voting by shareholders of Rio Tinto plc and Rio Tinto Limited on Joint Decisions, following the DLC Merger. The “DLC Dividend Share” was issued to facilitate the efficient management of funds within the DLC structure. Directors have the ability to issue an Equalisation Share if that is required under the terms of the DLC Merger Sharing Agreement. During 2018, US$140 million of shares and ADRs (2017: US$38.9 million; 2016: US$40.1 million) were purchased by employee share ownership trusts on behalf of Rio Tinto plc to satisfy future share options and awards as they vest. At 31 December 2018, 1,770,651 shares and 72,809 ADRs were held in the employee share ownership trusts on behalf of Rio Tinto plc. Information relating to share options and other share-based incentive schemes is given in note 43. Subsequent to 31 December 2018, 10,956,767 shares were bought back and cancelled under the on-market buy-back programme.

Share Capital - Rio Tinto Limit

Share Capital - Rio Tinto Limited	12 Months Ended
	Dec. 31, 2018
Disclosure Of Classes Of Share Capital [Abstract]
Share capital - Rio Tinto Limited	2018 2017 2016 Number Number Number 2018 2017 2016 (million) (million) (million) US$m US$m US$m Issued and fully paid up share capital At 1 January 412.41 424.19 424.19 4,140 3,915 3,950 Adjustment on currency translation (382 ) 310 (35 ) Ordinary shares purchased and cancelled (a) (b) (41.20 ) (11.78 ) - (281 ) (85 ) - At 31 December 371.21 412.41 424.19 3,477 4,140 3,915 – Special Voting Share (c) 1 only 1 only 1 only – DLC Dividend Share (c) 1 only 1 only 1 only Total share capital 371.21 412.41 424.19 (a) In November 2018, 41,198,134 Rio Tinto Limited ordinary shares were purchased at A$69.69 per share and cancelled under an off-market share buy-back programme carried out pursuant to the shareholder approval granted at Rio Tinto Limited’s 2018 annual general meeting for off-market and on-market buy-backs of up to 41.2 million Rio Tinto Limited ordinary shares. (b) In November 2017, 11,778,064 Rio Tinto Limited ordinary shares were purchased at A$63.67 per share and cancelled under an off-market share buy-back programme carried out pursuant to the shareholder approval granted at Rio Tinto Limited’s 2017 annual general meeting for off-market and on-market buy-backs of up to 42.4 million Rio Tinto Limited ordinary shares. (c) The “Special Voting Share” was issued to facilitate the joint voting by shareholders of Rio Tinto Limited and Rio Tinto plc on Joint Decisions following the DLC Merger. The “DLC Dividend Share” was issued to facilitate the efficient management of funds within the DLC structure. Directors have the ability to issue an Equalisation Share if that is required under the terms of the DLC Merger Sharing Agreement. During 2018, US$114 million of shares (2017: US$37.5 million; 2016: US$48.5 million) Information relating to share options and other share-based incentive schemes is given in note 43.

Other reserves and retained ear

Other reserves and retained earnings	12 Months Ended
	Dec. 31, 2018
Disclosure Of Other Reserves And Retained Earnings [Abstract]
Other reserves and retained earnings	2018 2017 2016 US$m US$m US$m Capital redemption reserve (a) At 1 January 38 34 34 Own shares purchased and cancelled 9 4 - At 31 December 47 38 34 Cash flow hedge reserve At 1 January 32 32 - Adjustment for transition to new accounting standards (note 45) (4 ) - - Cash flow hedge gains/(losses) 156 62 (88 ) Cash flow hedge losses/(gains) transferred to the income statement 40 (62 ) 116 Tax on the above (54 ) - 4 Transfers and other movements 25 - - At 31 December 195 32 32 Available for sale revaluation reserves At 1 January 20 (126 ) (139 ) Adjustment for transition to new accounting standards (note 45) (20 ) - - Gains on available for sale securities - 19 13 Losses on available for sale securities transferred to the income statement - 6 - Tax on the above - (1 ) - Transfers and other movements - 122 - At 31 December - 20 (126 ) Fair value through other comprehensive income reserve At 1 January - - - Adjustment for transition to new accounting standards (note 45) 8 - - Losses on equity investments (11 ) - - Transfers to retained earnings (3 ) - - At 31 December (6 ) - - Cost of hedging reserve At 1 January - - - Adjustment for transition to new accounting standards (note 45) 26 Cost of hedging deferred to reserves during the year (36 ) Transfer of cost of hedging to the income statement (3 ) - - At 31 December (13 ) - - Other reserves (b) At 1 January 11,714 11,861 11,735 Change in equity interest held by Rio Tinto - - 108 Own shares purchased from Rio Tinto Limited shareholders to satisfy share options (114 ) (64 ) (43 ) Employee share options: value of services 52 31 58 Deferred tax on share options (2 ) 10 3 Companies no longer consolidated - (124 ) - At 31 December 11,650 11,714 11,861 Foreign currency translation reserve (c) At 1 January 480 (2,585 ) (2,491 ) Parent and subsidiaries currency translation and exchange adjustments (3,658 ) 2,942 (204 ) Equity accounted units currency translation adjustments (48 ) 34 11 Currency translation reclassified on disposal 14 78 99 Transfers and other movements - 11 - At 31 December (3,212 ) 480 (2,585 ) Total other reserves per balance sheet 8,661 12,284 9,216 2018 2017 2016 US$m US$m US$m Retained earnings (d) At 1 January 23,761 21,631 19,736 Adjustment for transition to new accounting standards (note 45) (179 ) - - Parent and subsidiaries' profit for the year 13,125 8,423 4,298 Equity accounted units' profit after tax for the year 513 339 319 Actuarial gains/(losses) (e) 894 1 (94 ) Tax relating to components of other comprehensive income (269 ) (150 ) 30 Total comprehensive income for the year 14,263 8,613 4,553 Share buy-back programme (5,423 ) (2,312 ) - Dividends paid (5,356 ) (4,250 ) (2,725 ) Change in equity interest held by Rio Tinto 60 43 40 Companies no longer consolidated - 130 - Own shares purchased/treasury shares reissued for share options and other movements (140 ) (18 ) (37 ) Employee share options and other IFRS 2 charges taken to the income statement 61 57 64 Transfer from FVOCI reserve 3 - - Transfers and other movements (25 ) (133 ) - At 31 December 27,025 23,761 21,631 (a) The capital redemption reserve was set up to comply with section 733 of the UK Companies Act 2006 (previously section 170 of the UK Companies Act 1985) when shares of a company are redeemed or purchased wholly out of the company’s profits. Balances reflect the amount by which the company’s issued share capital is diminished in accordance with this section. (b) Other reserves includes US$11,936 million which represents the difference between the nominal value and issue price of the shares issued arising from Rio Tinto plc’s rights issue completed in July 2009. No share premium was recorded in the Rio Tinto plc financial statements through the operation of the merger relief provisions of the UK Companies Act 1985. Other reserves also include the cumulative amount recognised under IFRS 2 in respect of options granted but not exercised to acquire shares in Rio Tinto Limited, less, where applicable, the cost of shares purchased to satisfy share options exercised. The cumulative amount recognised under IFRS 2 in respect of options granted but not exercised to acquire shares in Rio Tinto plc is recorded in retained earnings. (c) Exchange differences arising on the translation of the Group’s net investment in foreign controlled companies are taken to the foreign currency translation reserve, as described in note 1(d). The cumulative differences relating to an investment are transferred to the income statement when the investment is disposed of. (d) Retained earnings and movements in reserves of subsidiaries include those arising from the Group’s share of joint operations. (e) There were no actuarial losses relating to equity accounted units in 2018, 2017 or 2016.

Financial instruments and risk

Financial instruments and risk management	12 Months Ended
	Dec. 31, 2018
Disclosure Of Financial Instruments [Abstract]
Financial instruments and risk management	Except where stated, the information given below relates to the financial instruments of the parent companies and their subsidiaries and joint operations, and excludes those of equity accounted units. The information is grouped in the following sections: A – Financial assets and liabilities by categories B – Derivative financial instruments C – Fair values A (a) Financial assets and liabilities by categories IFRS 9 Fair value Fair value through other through Amortised comprehensive profit and Total cost income loss At 31 December 2018 Note US$m US$m US$m US$m Financial assets Cash and cash equivalents 21 10,773 2,779 - 7,994 Trade and other financial receivables (a) (b) 18 3,007 2,015 - 992 Equity shares and quoted funds 20 130 - 53 77 Other investments, including loans (c) 20 2,782 6 - 2,776 Derivatives related to net debt: designated as hedges (d) 20, 24 70 - - 70 Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 20 432 - - 432 Embedded derivatives not related to net debt: designated as hedges (d) 20 54 - - 54 Loans to equity accounted units including quasi equity loans 167 167 - - Total financial assets 17,415 4,967 53 12,395 Financial liabilities Trade and other financial payables (e) 25 (5,552 ) (5,513 ) (39 ) Short-term borrowings and bank overdrafts 22 (312 ) (312 ) - Medium-term and long-term borrowings 22 (12,440 ) (12,440 ) - Derivatives related to net debt: designated as hedges (d) 22, 24 (358 ) - (358 ) Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 22 (98 ) - (98 ) Embedded derivatives not related to net debt: designated as hedges (d) 22 (46 ) - (46 ) Other financial liabilities 22 (666 ) (666 ) - Total financial liabilities (19,472 ) (18,931 ) (541 ) Notes to the 2018 financial statements continued 30 Financial instruments and risk management continued IAS 39 Held to maturity Available assets/other Loans and for sale Held at financial Total receivables securities fair value liabilities At 31 December 2017 Note US$m US$m US$m US$m US$m Financial assets Cash and cash equivalents 21 10,550 10,550 - - - Trade and other financial receivables (a) (b) 18 2,985 2,895 - 90 - Equity shares and quoted funds 20 136 - 136 - - Other investments, including loans (c) 20 1,152 15 - 1,125 12 Derivatives related to net debt: designated as hedges (d) 20, 24 99 - - 99 - Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 20 168 - - 168 - Loans to equity accounted units including quasi equity loans 198 198 - - - Total financial assets 15,288 13,658 136 1,482 12 Financial liabilities Trade and other financial payables (e) 25 (5,922 ) (15 ) (5,907 ) Short-term borrowings and bank overdrafts 22 (552 ) - (552 ) Medium-term and long-term borrowings 22 (14,624 ) - (14,624 ) Derivatives related to net debt: designated as hedges (d) 22, 24 (276 ) (276 ) - Other derivatives and embedded derivatives: not designated as hedges (d) 22 (255 ) (255 ) - Other financial liabilities 22 (345 ) - (345 ) Total financial liabilities (21,974 ) (546 ) (21,428 ) (a) Trade and other financial receivables comprise of trade receivables, other financial receivables, and amounts due from equity accounted units within note 18. (b) Under IFRS 9, provisionally priced receivables are fair valued. In the prior year, under IAS 39, only the embedded pricing derivatives, which were separated from the host receivables, were fair valued. (c) Other investments, including loans, comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets in managed investment funds classified as held for trading. (d) These financial assets and liabilities in aggregate agree to total derivative financial instruments disclosed in notes 20 and 22. (e) Trade and other financial payables comprise trade payables, other financial payables, accruals and amounts due to equity accounted units within note 25. The trade and other payables held at fair value are valued using level 2 inputs. A (b) Financial risk management Objectives and policy Rio Tinto’s policies on financial risk management are defined such that the Group has a capital structure in place to manage the organisation through the commodity cycle and that Group’s exposures may float with the market. Any exceptions to this general principle are formally approved. The Group is exposed to capital, liquidity, commodity price, credit, foreign exchange and interest rate risk. Rio Tinto does not acquire or issue derivative financial instruments for trading or speculative purposes; nor does it believe that it has material exposure to such trading or speculative holdings through its investments in joint arrangements and associates. However, derivatives are used as and when required in order to manage the Group’s exposure in accordance with its underlying financial risk management principles. A specialist team who have the appropriate skills and experience, with oversight from the treasurer, carries this out. Summarised below are the risks and the agreed policies to manage the risks identified above. (i) Capital and liquidity risk management The Group’s overriding objective when managing capital and liquidity is to safeguard the business as a going concern by maintaining a strong balance sheet whilst maximising returns for shareholders. The board and senior management regularly review the capital structure and liquidity of the Group taking into account: the Group’s strategic priorities, the economic and business conditions, and investment opportunities that have been identified, along with the expected returns to shareholders. The board expects total cash returns to shareholders over the longer term to be in a range of 40% to 60% of underlying earnings in aggregate throughout the commodity cycle. Their review considers various financial metrics. These include analysing net debt, gearing, the overall level of borrowings and their maturity profile, liquidity levels, total capital, future cash flows, EBITDA and interest cover ratios. Net debt decreased from US$3.8 billion at 31 December 2017 to net cash of US$0.3 billion at 31 December 2018 as operating cash inflows and divestment proceeds were partly offset by capital expenditure and cash returns to shareholders. At 31 December 2018 net gearing was ( Total capital for the Group is summarised below: 2018 2017 Total capital Note US$m US$m Equity attributable to owners of Rio Tinto (see Group balance sheet) 43,686 44,711 Equity attributable to non-controlling interests (see Group balance sheet) 6,137 6,404 Net debt 24 (255 ) 3,845 Total capital 49,568 54,960 Capital and liquidity risk management continued The Group has access to various forms of financing including its US Shelf Programme, European Debt Issuance Programme, Commercial Paper and credit facilities. The Group did not issue any listed debt in 2018 under these programmes. It also has access to a US$1.9 billion facility which was extended in 2018 and now matures in November 2021 with a one-year extension option and a US$5.6 billion facility (including a US$ denominated same day access swing-line facility) which matures in November 2022. The funds available can be used for general corporate purposes of the Group. At 31 December 2018 the facilities were undrawn. Advances under the revolving facilities bear an interest rate per annum based on LIBOR (or EURIBOR, CDOR or BBSW in relation to any euro, Canadian dollar or Australian dollar loans respectively) plus a margin (which is dependent on the Group’s long-term credit rating as determined by Moody’s and Standard & Poor’s and the level of drawdown). The facility agreements contain no financial covenants. The table below summarises the credit ratings attributed to the Group by Standard & Poor’s and Moody’s investor services as at 31 December. 2018 2017 Long-term rating (a) A/A3 A-/A3 Short-term rating (a) A-1/P-2 A-1/P-2 Outlook Stable/Stable Positive/Stable (a) On 6 February 2019 Moody's upgraded the Group's long-term credit rating to A2 and short-term credit rating to P-1 with a stable outlook. The unified credit status of the Group is maintained through cross-guarantees whereby contractual obligations of Rio Tinto plc and Rio Tinto Limited are automatically guaranteed by the other. During 2018, the Group redeemed bonds in aggregate with a notional principal value of US$1.9 billion (2017: US$2.5 billion) as part of the liability management programme. These bonds were issued by Rio Tinto Finance (USA) plc, Rio Tinto Finance plc and Rio Tinto Finance (USA) Limited. Due to early redemption costs this led to an aggregate cash outflow on those redemptions of US$2.0 billion (2017: US$2.7 billion) before fees. The table below summarises the maturity profile of the Group’s financial liabilities based on contractual undiscounted payments. It will therefore not necessarily agree with the amounts disclosed in the balance sheet. Financial liability analysis At 31 December 2018 Within 1 Between Between Between Between year or on 1 and 2 2 and 3 3 and 4 4 and 5 After demand years years years years 5 years Total (Outflows)/inflows US$m US$m US$m US$m US$m US$m US$m Non-derivative financial liabilities Trade and other financial payables (5,129 ) (423 ) - - - - (5,552 ) Borrowings before swaps (312 ) (562 ) (166 ) (660 ) (741 ) (10,476 ) (12,917 ) Expected future interest payments (a) (651 ) (653 ) (636 ) (630 ) (586 ) (4,082 ) (7,238 ) Other financial liabilities (666 ) - - - - - (666 ) Derivative financial liabilities (b) Derivatives related to net debt - net settled (36 ) (36 ) (36 ) (36 ) 4 (8 ) (148 ) Derivatives related to net debt - gross settled (a) – gross inflows 48 508 39 39 39 1,278 1,951 – gross outflows (79 ) (595 ) (58 ) (58 ) (58 ) (1,581 ) (2,429 ) Derivatives not related to net debt - net settled (27 ) (13 ) (5 ) (5 ) (5 ) (28 ) (83 ) Derivatives not related to net debt - gross settled: – gross inflows 1,664 - - - - - 1,664 – gross outflows (1,733 ) - - - - - (1,733 ) Total (6,921 ) (1,774 ) (862 ) (1,350 ) (1,347 ) (14,897 ) (27,151 ) At 31 December 2017 Within 1 Between Between Between Between year or on 1 and 2 2 and 3 3 and 4 4 and 5 After demand years years years years 5 years Total (Outflows)/inflows US$m US$m US$m US$m US$m US$m US$m Non-derivative financial liabilities Trade and other financial payables (5,488 ) (434 ) - - - - (5,922 ) Borrowings before swaps (552 ) (148 ) (1,011 ) (916 ) (1,283 ) (11,387 ) (15,297 ) Expected future interest payments (a) (679 ) (673 ) (670 ) (638 ) (606 ) (4,553 ) (7,819 ) Other financial liabilities (302 ) (43 ) - - - - (345 ) Derivative financial liabilities (b) Derivatives related to net debt - net settled 10 10 14 11 7 36 88 Derivatives related to net debt - gross settled (a) – gross inflows 62 62 958 44 44 1,493 2,663 – gross outflows (82 ) (82 ) (1,051 ) (55 ) (55 ) (1,741 ) (3,066 ) Derivatives not related to net debt - net settled (43 ) (36 ) (33 ) (24 ) (21 ) (138 ) (295 ) Derivatives not related to net debt - gross settled: – gross inflows 795 - - - - - 795 – gross outflows (802 ) - - - - - (802 ) Total (7,081 ) (1,344 ) (1,793 ) (1,578 ) (1,914 ) (16,290 ) (30,000 ) (a) Interest payments have been projected using interest rates applicable at the end of the applicable financial year. Where debt is subject to variable interest rates, future interest payments are subject to change in line with market rates. (b) The maturity grouping is based on the earliest payment date. Offsetting and enforceable master netting agreements Financial assets and liabilities are offset and the net amount reported in the consolidated balance sheet when there is a legally enforceable right to offset the recognised amounts and there is an intention to settle on a net basis or realise the asset and settle the liability simultaneously. There were no material amounts offset in the balance sheet and no material enforceable master netting agreements were identified. (ii) Commodity price risk The Group’s normal policy is to sell its products at prevailing market prices. Exceptions to this rule are subject to strict limits laid down by the board and to rigid internal controls. The Group’s products are sold to customers under contracts which vary in tenure and pricing mechanisms, including some volumes sold in the spot market. Sales revenue may be subject to adjustment if the product specification does not conform to the terms specified in the sales contract. Pricing for iron ore is on a range of terms, the majority being either monthly or quarterly average pricing mechanisms, with a smaller proportion of iron ore volumes being sold on the spot market. Copper and aluminium are generally sold under contracts which vary in tenure and pricing mechanisms, with some volumes sold in the spot market. The prices are determined by reference to prevailing market prices on terminal markets, such as the London Metal Exchange (LME) and the Commodities Exchange (COMEX) in New York. Prices fluctuate widely in response to changing levels of supply and demand but, in the long run, prices are related to the marginal cost of supply. Gold is also priced in an active market in which prices respond to daily changes in quantities offered and sought. Newly mined gold is only one source of supply; investment and disinvestment can be important elements of supply and demand. Certain of the Group’s products may be provisionally priced at the date revenue is recognised; however, substantially all iron ore and aluminium sales are reflected at final prices in the results for the period. The final selling price for all provisionally priced products is based on the price for the quotational period stipulated in the contract. Final prices for copper concentrate are normally determined between 30 and 180 days after delivery to the customer. The change in value of the provisionally priced receivable is based on relevant forward market prices and is included in sales revenue. As at 31 December 2018, the Group had 240 277 37 The Group is also exposed to changes in commodity prices on purchases of raw materials and consumables. Notes to the 2018 financial statements continued 30 Financial instruments and risk management continued Hedging strategy Rio Tinto’s exposure to commodity prices is diversified by virtue of its broad commodity base and the Group does not generally consider that commodity fixed price hedging would provide a long-term benefit to shareholders. In order to mitigate the Group’s exposure to changes in the relationship between aluminium price and power prices, the Group has a number of electricity purchase contracts which are directly linked to the daily official LME cash ask price for high grade aluminium (“LME price”) and to the US Midwest Transaction Premium (“Midwest premium”). On transition to IFRS 9, the Group elected to apply hedge accounting to two existing embedded derivatives within the Group’s power contracts. The embedded derivatives (notional aluminium forward sales) have been designated as the hedging instrument, with the forecasted aluminium sales, priced using the LME price and the Midwest premium, representing the hedged item. The hedging ratio is 1:1 as the quantity of sales designated as being hedged matches the notional amount of the hedging instrument. The hedging instrument’s notional amount, expressed in equivalent metric tonnes of aluminium, is derived from the expected electricity consumption under the power contracts as well as other relevant contract parameters. When such embedded derivatives are designated as the hedging instrument in a cash flow hedge, the effective portion of the change in the fair value of the hedging instrument is recognised in other comprehensive income and accumulated in the cash flow hedge reserve. The amount that is recognised in other comprehensive income is limited to the lesser of the cumulative change in the fair value of the hedging instrument and the cumulative change in the fair value of the hedged item, in absolute terms. Any ineffectiveness relating to the hedging relationship is recognised immediately in the income statement. Sources of ineffectiveness include: differences in the timing of the cash flows between the hedged item and the hedging instrument, non-zero initial fair value of the hedging instrument, the existence of a cap on the Midwest premium in the hedging instrument and counterparty credit risk. The Group is holding the following notional aluminium forward sales contracts embedded in the power contracts: At 31 December 2018 Within 1 year Between 1 and 5 years Between 5 and 10 years After 10 years Notional amount (in tonnes) 56,481 286,666 358,416 65,548 Notional amount (in US$ millions) 114 634 870 168 Average hedged rate (in US$ per tonne) 2,013 2,210 2,426 2,562 The impact of the hedging instrument on the Group balance sheet is as follows: At 31 December 2018 Notional amount US$m Carrying value US$m Line item in the statement of financial position Change in fair value used for measuring ineffectiveness for the period US$m Aluminium embedded derivatives separated from the power contract (a) 1,786 8 Other financial asset (US$54m) and other financial liability (US$46m) 205 (a) Aluminium embedded derivatives (forward contracts and options) are contained within certain aluminium smelter electricity purchase contracts. The impact of the hedged item on the Group balance sheet is: At 31 December 2018 Change in fair value used for measuring ineffectiveness for the period US$m Cash flow hedge reserve US$m Highly probable forecast aluminium sales (182) 179 The effect of the cash flow hedge in the statement of profit or loss and other comprehensive income (OCI) is: At 31 December 2018 Total hedging gain recognised in OCI US$m Ineffectiveness recognised in profit or loss US$m Line item in the statement of profit or loss Amount reclassified from OCI to profit or loss US$m Line item in the statement of profit or loss Highly probable forecast aluminium sales 181 24 Net operating costs (raw materials, consumables, repairs and maintenance) 2 Consolidated sales revenue There was no cost of hedging recognised during 2018 relating to this hedge relationship. Details of commodity derivatives not designated as hedges held at 31 December 2018 are set out in section B. Sensitivities The Group’s commodity derivatives are impacted by changes in market prices. The table below summarises the impact that changes in aluminium market prices have on those aluminium forward and option contracts embedded in power supply agreements outstanding at 31 December 2018. There will be an offsetting change in future Group earnings with any changes in price. Change in market prices 2018 US$m 2017 US$m Effect on net earnings +10% (102) (203) -10% 35 212 Effect on equity +10% (101) - -10% 103 - The Group’s “own use contracts” are excluded from the sensitivity analysis as they are outside the scope of IFRS 9. Such contracts to buy or sell non-financial items continue to be held for the purpose of the receipt or delivery of the non-financial item in accordance with the business unit’s expected purchase, sale or usage requirements. (iii) Credit risk Credit risk is the risk that a counterparty will not meet its obligations under a financial instrument or customer contract, leading to a financial loss. The Group is exposed to credit risk from its operating activities (primarily from customer receivables) and from its financing activities, including investments in treasury and liquidity funds, deposits with banks and financial institutions, other short-term investments, interest rate and currency derivative contracts and other financial instruments. Credit risks related to receivables Customer credit risk is managed by the Commercial team subject to the Group’s established policy, procedures and controls relating to customer credit risk management. Credit limits are established for all customers based on internal or external rating criteria. Where customers are rated by an independent credit rating agency, these ratings are used to set credit limits. In circumstances where no independent credit rating exists, the credit quality of the customer is assessed based on a credit rating scorecard. Outstanding customer receivables are regularly monitored and any credit concerns highlighted to senior management. At 31 December 2018, the Group had approximately 113 % 17 34 Credit risk related to financial instruments and cash deposits Credit risk from investments in government securities (primarily US Government), corporate and asset-backed securities or money market funds, and balances with banks and financial institutions is managed by Group Treasury in accordance with a board-approved policy. Investments of surplus funds are made only with approved investment grade (BBB- and above) counterparties who have been assigned specific credit limits. The board reviews these annually. The limits are set to minimise the concentration of credit risk and therefore mitigate the potential for financial loss through counterparty failure. The maximum credit risk exposure of the Group’s financial assets at the balance sheet date is as follows: 2018 2017 Note US$m US$m Cash and cash equivalents 21 10,773 10,550 Trade and other financial receivables 18 3,007 2,985 Investments 20 2,782 1,152 Derivative assets 20 556 267 Loans to equity accounted units 38 39 Total 17,156 14,993 (iv) Foreign exchange risk The Group’s earnings, cash flows and shareholders’ equity are influenced by a wide variety of currencies due to the geographic diversity of the Group’s sales and the countries in which it operates. The US dollar is the currency in which the majority of the Group’s sales are denominated. Operating costs are influenced by the currencies of those countries where the Group’s mines and processing plants are located and also by those currencies in which the costs of imported equipment and services are determined. Apart from the US dollar, the Australian and Canadian dollars are the most important currencies (apart from the US dollar) influencing costs. In any particular year, currency fluctuations may have a significant impact on Rio Tinto’s financial results. A strengthening of the US dollar against the currencies in which the Group’s costs are partly denominated has a positive effect on Rio Tinto’s underlying earnings. However, a strengthening of the US dollar does reduce the value of non-US dollar-denominated net assets and therefore total equity. Borrowings and cash are predominantly denominated in US dollars, either directly or through the use of derivatives, as it is the most appropriate currency for financing the Group’s operations. The majority of debt and other financial assets and liabilities including intragroup balances, are held in the functional currency of the relevant subsidiary. In a small number of instances, US dollar debt and other financial assets and liabilities, including intragroup balances, are held in currencies other than the functional currency of the relevant subsidiary. This results in an accounting exposure to exchange gains and losses as the financial assets and liabilities are translated into the functional currency of the subsidiary that holds those assets and liabilities. These exchange gains and losses are recorded in the Group’s income statement except to the extent that they can be taken to equity under the Group’s accounting policy which is explained in note 1(d). The Group’s income statement includes realised and unrealised exchange gains/losses arising on US dollar external borrowings and intragroup balances in entities with a non-US dollar functional currency. On translation to the Group’s US dollar presentation currency, there is a corresponding and offsetting exchange difference on translation of these balances which is recognised directly in the currency translation reserve. There is no impact on total equity. Gains and losses on US dollar net debt and on non-trading intragroup balances are excluded from underlying earnings. Other exchange gains and losses are included in underlying earnings. See section B for the details of cross-currency interest rate swaps relating to borrowings. The table below summarises, by currency, the Group’s net debt, after taking into account relevant cross-currency interest rate swaps and foreign exchange contracts: Total Derivatives Cash and Net cash/ Net cash/ borrowings related to net cash Other (debt) (debt) excluding overdrafts debt equivalents investments 2018 2017 Net cash/(debt) by currency US$m US$m US$m US$m US$m US$m US dollar (12,080 ) (288 ) 10,310 2,522 464 (3,628 ) Australian dollar (472 ) - 217 - (255 ) (208 ) Euro (39 ) - 17 - (22 ) (58 ) South African rand - - 95 - 95 59 Canadian dollar (157 ) - 23 - (134 ) (148 ) Other (3 ) - 110 - 107 138 Total (12,751 ) (288 ) 10,772 2,522 255 (3,845 ) Hedging strategy Under normal market conditions, the Group does not consider that active currency hedging of transactions would provide long-term benefits to shareholders. The Group reviews its exposure on a regular basis and will undertake hedging if deemed appropriate. Currency protection measures may be deemed appropriate in specific commercial circumstances. Capital expenditures and other significant financial items such as acquisitions, disposals, tax and dividend cash flows may be hedged subject to strict limits laid down by the board. Refer to section B for details of the cross-currency interest rate swaps, and the currency forward and option contracts used to manage the currency risk exposures of the Group at 31 December 2018. Sensitivities The table below gives the estimated retranslation effect on financial assets and financial liabilities, including intragroup balances, of a 10% strengthening in the closing exchange rate of the US dollar against significant currencies. 10% is the annual exchange rate movement that management deems to be reasonably probable (on an annual basis over the long run) for one of the Group’s significant currencies and as such provides an appropriate representation. Sensitivities are calculated in the functional currencies of individual Group entities. The impact of these on net earnings and underlying earnings is translated into US dollars at the year-end exchange rates present in note 41. The sensitivity associated with a 10% weakening of a particular currency would be broadly equal and opposite within equity to the figures presented below. The impact is expressed in terms of the effect on net earnings, underlying earnings and equity, assuming that each exchange rate moves in isolation. The sensitivities are based on financial assets and financial liabilities held at 31 December 2018, where balances are not denominated in the functional currency of the subsidiary or joint operation, and exclude financial assets and liabilities held by equity accounted units. These balances will not remain constant throughout 2019, and therefore the following information should be used with care. At 31 December 2018 Gains/(losses) associated with 10% strengthening of the US dollar Of which amount Closing Effect on impacting Impact exchange net underlying directly rate earnings earnings on equity Currency exposure US cents US$m US$m US$m Australian dollar 70 346 1 (993 ) Canadian dollar 73 (82 ) 7 - Euro 114 202 5 - Notes to the 2018 financial statements continued 30 Financial instruments and risk management continued At 31 December 2017 Gains/(losses) associated with 10% strengthening of the US dollar Of which amount Closing Effect on impacting Impact exchange net underlying directly rate earnings earnings on equity Currency exposure US cents US$m US$m US$m Australian dollar 78 608 47 (1,657 ) Canadian dollar 79 (134 ) 3 - Euro 120 165 (2 ) - 10% is the annual exchange rate movement that management deems to be reasonably probable (on an annual basis over the long run) for one of the Group’s significant currencies and as such provides an appropriate representation. Sensitivities are calculated in the functional currencies of individual Group entities and the impact on net and underlying earnings translated into US dollars at the year-end exchange rates presented in note 41. (v) Interest rate risk Interest rate risk refers to the risk that the value of a financial instrument or cash flows associated with the instrument will fluctuate due to changes in market interest rates. The Group’s interest rate management policy is generally to borrow and invest at floating interest rates. This approach is based on the historically lower cost of borrowing at floating rates and historical correlation between interest rates and commodity prices. However, in certain circumstances the Group may elect to maintain a higher proportion of fixed-rate funding. Hedging strategy As noted above, the Group hedges its interest rate risk by entering into interest rate derivatives to achieve its policies. The Group reviews the positions on a regular basis. During 2018, in conjunction with its liability management programme million (2017: US$2 million). The interest rate swaps were in fair value hedge relationships prior to being closed out. At the end of 2018, US$ 10.2 79 21 See note 22 for the details of outstanding debt and hedging arrangements with regard to debt at 31 December 2018. Sensitivities Based on the floating rate financial instruments outstanding at 31 December 2018, the effect on net earnings of a 100 basis point increase in US dollar LIBOR interest rates, with all other variables held constant, would be an income of US$8 million (2017: charge of US$8 million) due to the net cash position in 2018 versus the net debt position in 2017. The Group has an exposure to interest rate volatility within shareholders’ equity arising from fair value movements on derivatives in the cash flow hedge reserve. These derivatives have an underlying exposure to sterling and US dollars. With all factors remaining constant, and based on the composition of derivatives impacting the cash flow reserve at 31 December 2018, the sensitivity of a 100 basis point increase in interest rates in each of the currencies in isolation would impact equity, before tax, by a charge of US$ 69 78 Notes to the 2018 financial statements continued 30 Financial instruments and risk management continued B Derivative financial instruments The Group’s derivatives, including embedded derivatives, as at 31 December, are summarised below. Total fair value 2018 2017 Asset Liability Asset Liability US$m US$m US$m US$m Derivatives designated as hedges Interest rate swaps (a) 70 (137 ) 99 (127 ) Cross-currency interest rate swaps (b) - (221 ) - (149 ) Aluminium embedded derivatives (c) 54 (46 ) - - Total derivatives designated as hedges 124 (404 ) 99 (276 ) Derivatives not designated as hedges Currency forward contracts, options and swaps - (68 ) 7 (2 ) Aluminium forward contracts (d) 26 (19 ) 21 (9 ) Aluminium embedded derivatives (c) 346 - 140 (238 ) Other embedded derivatives 6 - - (5 ) Other commodity contracts 54 (11 ) - (1 ) Total derivatives not designated as hedges 432 (98 ) 168 (255 ) Total derivative instruments 556 (502 ) 267 (531 ) Analysed by maturity: Less than 1 year 88 (95 ) 29 (50 ) Between 1 and 5 years 153 (205 ) 31 (233 ) More than 5 years 315 (202 ) 207 (248 ) Total 556 (502 ) 267 (531 ) Total net derivative instruments 54 (264 ) 2018 2017 Reconciliation to balance sheet Note US$m US$m Non-current assets 20 468 238 Current assets 20 88 29 Current liabilities 22 (95 ) (50 ) Non-current liabilities 22 (407 ) (481 ) Total net derivative instruments 54 (264 ) (a) The interest rate swaps are used to convert certain fixed rate borrowings to a floating rate. For further details, see note 22. (b) The cross-currency interest rate swaps are used to convert non-US dollar denominated borrowings to either fixed or floating US dollar borrowings. For further details see note 22. (d) Aluminium embedded derivatives (forward contracts and options) are contained within certain aluminium smelter electricity purchase contracts. These contracts reduce the Group’s margin exposure to movements in the aluminium price. (c) The aluminium forward contracts are entered into to convert aluminium sales made at a fixed price to the market price (LME cash). In 2017 and 2018 these contracts were not designated as hedges. C Fair values The carrying amounts and fair values of all of the Group’s financial instruments which are not carried at an amount which approximates their fair value at 31 December 2018 and 31 December 2017 are shown in the following table. The fair values of the Group’s cash equivalents and loans to equity accounted units approximate their

Contingencies and commitments

Contingencies and commitments	12 Months Ended
	Dec. 31, 2018
Disclosure Of Commitments And Contingent Liabilities [Abstract]
Contingencies and commitments	2018 2017 US$m US$m Capital commitments excluding the Group's share of joint venture capital commitments Within 1 year 1,742 2,052 Between 1 and 3 years 439 531 Between 3 and 5 years 66 58 After 5 years 36 - Total 2,283 2,641 Group's share of joint venture capital commitments Within 1 year 115 29 Between 1 and 3 years 1 - Total 116 29 Our capital commitments include open purchase orders for managed operations and expenditure on major projects already authorised by our Investment Committee for non-managed operations. On a legally enforceable basis, capital commitments would be approximately US$0.4 billion (2017: US$0.5 billion) as many of the contracts relating to the Group’s projects have various cancellation clauses. Unrecognised commitments to contribute funding or resources to joint ventures We have a commitment to purchase and market a portion (in excess of the Group’s ownership interest) of the output of Sohar Aluminium Company L.L.C., an aluminium smelter in which the Group is a joint venture partner. The Group immediately sells the purchased products to third parties. Along with the other joint venture partners, we have commitments to provide emergency funding (ie funding required to preserve the life or assets of the company or to comply with applicable laws) if required by Sohar Aluminium Company L.L.C., subject to approved thresholds. At 31 December 2018, Minera Escondida Limitada held an undrawn shareholder line of credit for US$225 million (Rio Tinto share: 31 December 2017: US$225 million). The current facility will mature in September 2019. Operating leases The aggregate amounts of minimum lease payments under non-cancellable operating leases are as follows: 2018 2017 US$m US$m Within 1 year 475 397 Between 1 and 3 years 587 542 Between 3 and 5 years 270 313 After 5 years 385 593 Total 1,717 1,845 Operating leases include leases of dry bulk vessels and offices as well as other property, plant and equipment. The terms of lease payments vary, with a significant proportion being fixed rate and including renewal options. Leases for dry bulk vessels include costs for crewing services. The Group will implement IFRS 16 “Leases” as at 1 January 2019; refer to note 1. Purchase obligations The aggregate amount of future payment commitments under purchase obligations outstanding at 31 December was: Adjusted (a) 2018 2017 US$m US$m Within 1 year 2,804 2,874 Between 1 and 2 years 1,565 1,712 Between 2 and 3 years 1,344 1,401 Between 3 and 4 years 1,097 1,282 Between 4 and 5 years 882 1,026 After 5 years 9,358 11,185 Total 17,050 19,480 (a) Purchase obligations are enforceable and legally binding agreements to buy goods or services. They specify all significant terms, including: fixed or minimum quantities to be purchased or consumed; fixed, minimum or variable price provisions; and the approximate timing of the transactions. Purchase obligations for goods mainly relate to purchases of raw materials and consumables and purchase obligations for services mainly relate to charges for the use of infrastructure, commitments to purchase power and freight contracts. These goods and services are expected to be used in the business. To the extent that this changes, a provision for onerous obligations may be made as described in note 1(i). Purchases from joint arrangements or associates are included if the quantity purchased is in excess of our ownership interest in the entity. However, purchase obligations exclude contracted purchases of bauxite, alumina and aluminium from joint arrangements and associates and contracted purchases of alumina from third parties. This is because these purchases are made for commercial reasons and the Group is, overall, a net seller of these commodities. As described above, we also have a commitment to buy and market a portion (in excess of our ownership interest) of the output of Sohar Aluminium Company L.L.C. 2018 2017 US$m US$m Contingent liabilities (subsidiaries and joint operations) Indemnities and other performance guarantees (a) (b) 317 552 (a) Indemnities and other performance guarantees represent the potential outflow of funds from the Group for the satisfaction of obligations including those under contractual arrangements (for example undertakings related to supplier agreements) not provided for in the balance sheet, where the likelihood of the guarantees or indemnities being called is assessed as possible rather than probable or remote. (b) There were no material contingent liabilities arising in relation to the Group’s joint ventures and associates. Contingent liabilities In October 2017, Rio Tinto announced that it had been notified by the US Securities and Exchange Commission (SEC) that the SEC had filed a complaint in relation to Rio Tinto’s disclosures and timing of the impairment of Rio Tinto Coal Mozambique (RTCM). The impairment was reflected in Rio Tinto’s 2012 year-end accounts. The SEC alleges that Rio Tinto, a former chief executive, Tom Albanese, and a former chief financial officer, Guy Elliott, committed violations of the anti-fraud, reporting, books and records and internal control provisions of the federal securities law by not accurately disclosing the value of RTCM and not impairing it when Rio Tinto published its 2011 year-end accounts in February 2012 or its 2012 interim results in August 2012. In October 2017, an associated US class action was commenced on behalf of securities holders. In March 2018, the Australian Securities and Investments Commission (ASIC) filed civil proceedings in the NSW District Registry of the Federal Court of Australia against Rio Tinto Limited, Albanese, and Elliott. On 1 May 2018, ASIC expanded its proceedings. ASIC alleges that Rio Tinto committed violations of the disclosure, accounting, and misleading or deceptive conduct provisions of the Corporations Act by making misleading or deceptive statements related to RTCM in its 2011 Annual report and its 2012 interim financial statements, not complying with accounting standards in respect of its 2012 interim financial statements, and not disclosing an impairment of RTCM in its 2012 interim financial statements. ASIC further alleges Albanese and Elliott breached their duties as directors or officers, and failed to take all reasonable steps to comply with relevant accounting requirements. Rio Tinto believes that the SEC case and the ASIC proceedings are unwarranted and that, when all the facts are considered by the courts, the claims will be rejected. Rio Tinto will defend the allegations vigorously. In October 2017, Rio Tinto reached a settlement with the UK’s Financial Conduct Authority (FCA) related to the timing of the impairment of RTCM, with the FCA determining that Rio Tinto had breached the FCA's Disclosure and Transparency Rules, imposing a financial penalty on Rio Tinto of £27.4 million (US$36.4 million). It is important to stress that the FCA made no findings of fraud, or of any systemic or widespread failure by Rio Tinto. This separate FCA case is now closed. In addition, Rio Tinto continues to co-operate fully with relevant authorities in connection with their investigations in relation to contractual payments totalling US$10.5 million made to a consultant who had provided advisory services in 2011 on the Simandou project in Guinea. In August 2018, the court dismissed a related US class action commenced on behalf of securities holders. The outcomes of these matters remain uncertain, but they could ultimately expose the Group to material financial cost. The board is giving these matters its full and proper attention and a dedicated board committee continues to monitor the progress of these matters. The Group is monitoring developments in relation to EU State Aid investigations including the EU Commission’s State Aid investigation into the UK’s Controlled Foreign Company taxation regime. The Group does not currently consider that any provision is required in relation to EU State Aid. Notes to the 2018 financial statements continued 31 Contingencies and commitments continued Guarantees by parent companies Rio Tinto plc and Rio Tinto Limited have, jointly and severally, fully and unconditionally guaranteed the following securities issued by the following 100% owned finance subsidiaries: US$ Rio Tinto plc has provided a guarantee, known as the completion support undertaking (CSU), in favour of the Oyu Tolgoi LLC project finance lenders. At 31 December 2018, US$4.3 The Rio Tinto guarantee applies to the extent that Turquoise Hill Resources Ltd cannot satisfy Oyu Tolgoi LLC’s project finance debt servicing obligations under its own guarantee to the lenders, called the sponsor debt service undertaking (DSU). Both the CSU and DSU contain a carve-out for certain political risk events. Contingent assets The Group has, from time to time, various insurance claims outstanding with reinsurers.

Average number of employees

Average number of employees	12 Months Ended
	Dec. 31, 2018
Number And Average Number Of Employees [Abstract]
Average number of employees	Subsidiaries and joint operations Equity accounted units (Rio Tinto share) Group total 2018 2017 2016 2018 2017 2016 2018 2017 2016 Principal locations of employment: Australia and New Zealand 19,017 19,041 20,489 578 602 849 19,595 19,643 21,338 Canada 10,620 10,256 10,239 - - - 10,620 10,256 10,239 UK 287 309 487 - - - 287 309 487 Europe 1,418 1,505 1,722 - - - 1,418 1,505 1,722 Africa 3,496 3,461 4,875 1,262 1,269 1,270 4,758 4,730 6,145 US 3,792 3,429 3,196 - - - 3,792 3,429 3,196 Mongolia 2,886 2,861 2,737 - - - 2,886 2,861 2,737 Indonesia 1,615 1,642 2,862 - - - 1,615 1,642 2,862 South America 210 197 166 1,289 1,237 1,388 1,499 1,434 1,554 Other countries (a) 988 998 749 - - - 988 998 749 Total 44,329 43,699 47,522 3,129 3,108 3,507 47,458 46,807 51,029 (a) “Other countries” primarily includes employees in the Middle East (excluding Oman which is included in Africa), India, Singapore and other countries in Asia which are not shown separately in the table above. For the year ended 31 December 2018, the average number of employees in Singapore was 422 (2017: 434; 2016: 262) and the average number of employees in India was 288 (2017: 310; 2016: 280). Employee numbers, which represent the average for the year, include 100% of employees of subsidiary companies. Employee numbers for joint operations and equity accounted units are proportional to the Group’s interest under contractual agreements. Average employee numbers include a part-year effect for companies acquired or disposed of during the year. Part-time employees are included on a full-time equivalent basis. Temporary employees are included in employee numbers. People employed by contractors are not included.

Principal subsidiaries

Principal subsidiaries	12 Months Ended
	Dec. 31, 2018
Disclosure Of Significant Investments In Subsidiaries [Abstract]
Principal subsidiaries	Notes to the 2018 financial statements continued At 31 December 201 Company and country of incorporation/ operation Principal activities Class of shares held Proportion of class held (%) Group interest (%) Non-controlling interest (%) Australia Argyle Diamonds Limited Mining and processing of diamonds Ordinary 100 100 - Dampier Salt Limited Salt and gypsum Ordinary 68.36 68.36 31.64 Energy Resources of Australia Limited Uranium mining Ordinary 68.39 68.39 31.61 Hamersley Iron Pty Limited Iron ore mining Ordinary 100 100 - North Mining Limited (a) Iron ore mining Ordinary 100 100 - Queensland Coal Pty Limited (b) Coal mining Ordinary 100 100 - Rio Tinto Aluminium (Holdings) Limited Bauxite mining; alumina production; primary aluminium smelting Ordinary 100 100 - Robe River Mining Co Pty Ltd (a) Iron ore mining Class A 40 60 40 Class B 76.36 Brazil Alcan Alumina Ltda. (c) Alumina production and bauxite mining Quota 100 100 - Canada Iron Ore Company of Canada (d) Iron ore mining; iron ore pellets Common 58.72 58.72 41.28 Rio Tinto Fer et Titane Inc. Titanium dioxide feedstock; high purity iron and steel Common 100 100 - Class B preference 100 100 - CAD 0.01 preferred 100 100 - Rio Tinto Alcan Inc. Bauxite mining; alumina refining; aluminium smelting Common 100 100 - Diavik Diamond Mines (2012) Inc. (e) Diamond mining and processing Common 100 100 - Guinea Simfer Jersey Limited (f) Iron ore project Ordinary 53 53 47 Madagascar QIT Madagascar Minerals SA (g) Ilmenite mining Common 80 80 Investment certificates 100 100 15 Voting certificates 80 80 20 Mongolia Turquoise Hill Resources Ltd (including Oyu Tolgoi LLC) (h) Copper and gold mining Common 50.79 50.79 49.21 Namibia Rössing Uranium Limited ( i ) Uranium mining B N$1 71.22 68.62 31.38 C N10c 70.59 South Africa Richards Bay Titanium (Proprietary) Limited (j) Titanium dioxide;high purity iron production B Ordinary 100 B preference 100 74 26 Parent Preference 100 Richards Bay Mining (Proprietary) Limited (j) Ilmenite, rutile and zircon mining B Ordinary 100 B preference 100 74 26 Parent Preference 100 US Kennecott Holdings Corporation (including Kennecott Utah Copper and Kennecott Exploration) Copper and gold mining, smelting and refining and exploration activities Common US$0.01 100 100 - U.S. Borax Inc. Mining, refining and marketing of borates Common US$0.10 100 100 - This list includes only those companies that have a more significant impact on the profit or assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s principal subsidiaries are mostly held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) Robe River Mining Co Pty Ltd (which is 60% owned by the Group) holds a 30% interest in Robe River Iron Associates (Robe River). North Mining Ltd (which is wholly owned by the Group) holds a 35% interest in Robe River. Through these companies the Group recognises a 65% share of the assets, liabilities, revenues and expenses of Robe River, with a 12% non-controlling interest. The Group therefore has a 53% beneficial interest in Robe River. (b) Queensland Coal Pty Limited was the main legal entity that held the Group’s interests in Hail Creek (82%) and Kestrel (80%). These were unincorporated arrangements that were not entities; the Group recognised its share of assets, liabilities, revenues and expenses relating to these arrangements. On 1 August 2018, the Group sold its 82% interest in the Hail Creek coal mine and its 80% interest in the Kestrel underground coal mine. (c) Alcan Alumina Ltda holds the Group’s 10% interest in Consórcio De Alumínio Do Maranhão, a joint operation in which the Group participates but is not a joint operator. The Group recognises its share of assets, liabilities, revenues and expenses relating to this arrangement. (d) Iron Ore Company of Canada is incorporated in the US, but operates in Canada. (e) Diavik Diamond Mines (2012) Inc. (DDMI) is the legal entity that owns the Group’s 60% interest in the Diavik Joint Venture, an unincorporated arrangement. The Group recognises its share of assets, revenue and expenses relating to this arrangement. Liabilities are recognised according to DDMI’s contractual obligations, with a corresponding 40% receivable or contingent asset representing the co-owner’s share where applicable. (f) Simfer Jersey Limited, a company incorporated in Jersey in which the Group has a 53% interest, has an 85% interest in Simfer S.A. the company that operates the Simandou mining project in Guinea. The Group therefore has a 45.05% indirect interest in Simfer S.A. These entities are consolidated as subsidiaries and together referred to as the Simandou iron ore project. (g) The Group’s shareholding in QIT Madagascar Minerals SA carries an 80% economic interest and 80% of the total voting rights; a further 5% economic interest is held through non-voting investment certificates to give an economic interest of 85%. The non-controlling interests have a 15% economic interest and 20% of the total voting rights. (h) The Group has a 50.79% interest in Turquoise Hill Resources Ltd, which holds a 66% interest in Oyu Tolgoi LLC (OT) which is a subsidiary of Turquoise Hill Resources Ltd. The Group therefore has a 33.5% indirect interest in OT. Turquoise Hill Resources Ltd is incorporated in Canada but operates principally in Mongolia. ( i ) The Group’s shareholding in Rössing Uranium Limited entitles it to 35.57% of the total voting rights; the non-controlling interests hold 64.43% of the total voting rights. Rössing is consolidated by virtue of the Group’s board control. The Government of Namibia has the ability to veto matters that are considered not to be in the interest of Namibia; this is considered to be a protective right. Rio Tinto therefore has control of Rössing and consolidates it as a subsidiary. At 31 December 2018, assets and liabilities held for sale included our entire interest in Rössing Uranium Limited. (j) Additional classes of shares issued by Richards Bay Titanium (Proprietary) Limited and Richards Bay Mining (Proprietary) Limited representing non-controlling interests are not shown. The Group’s total legal and beneficial interest in Richards Bay Titanium (Proprietary) Limited and Richards Bay Mining (Proprietary) Limited is 74%. Summary financial information for subsidiaries that have non-controlling interests that are material to the Group This summarised financial information is shown on a 100% basis. It represents the amounts shown in the subsidiaries’ financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments, and before intercompany eliminations. Iron Ore Company of Canada Iron Ore Company of Canada Energy Resources of Australia Energy Resources of Australia Turquoise Hill (a)(b) Turquoise Hill (a)(b) 2018 2017 2018 2017 2018 2017 US$m US$m US$m US$m US$m US$m Revenue 1,561 1,867 151 157 1,180 940 Profit/(loss) after tax 298 377 (241 ) (29 ) 139 22 – attributable to non-controlling interests 122 156 1 (9 ) 14 (49 ) – attributable to Rio Tinto 176 221 (242 ) (20 ) 125 71 Other comprehensive (loss)/income (136 ) 144 2 - (4 ) 4 Total comprehensive income/(loss) 162 521 (239 ) (29 ) 135 26 Non-current assets 2,376 2,535 74 57 10,375 9,008 Current assets 459 714 311 406 3,813 4,953 Current liabilities (351 ) (449 ) (123 ) (128 ) (540 ) (504 ) Non-current liabilities (791 ) (838 ) (522 ) (356 ) (4,367 ) (4,311 ) Net assets/(liabilities) 1,693 1,962 (260 ) (21 ) 9,281 9,146 – attributable to non-controlling interests 699 809 (6 ) (7 ) 3,936 3,982 – attributable to Rio Tinto 994 1,153 (254 ) (14 ) 5,345 5,164 Cash flow from operations 553 840 (64 ) (2 ) 357 295 Dividends paid to non-controlling interests (178 ) (162 ) - - - - (a) Turquoise Hill Resources Ltd holds a controlling interests in OT. (b) Under the terms of the project finance facility held by OT, there are certain restrictions on the ability of OT to make shareholder distributions. Notes to the 2018 financial statements continued 33 Principal subsidiaries continued Robe River Mining Co Pty Robe River Mining Co Pty Other companies and eliminations (c) Other companies and eliminations (c) Robe River Robe River 2018 2017 2018 2017 2018 2017 US$m US$m US$m US$m US$m US$m Revenue 1,082 1,164 1,262 1,351 2,344 2,515 Profit after tax 561 617 543 637 1,104 1,254 – attributable to non-controlling interests 218 242 - - 218 242 – attributable to Rio Tinto 343 375 543 637 886 1,012 Other comprehensive (loss)/income (313 ) 238 (203 ) 158 (516 ) 396 Total comprehensive income 248 855 340 795 588 1,650 Non-current assets 2,610 2,927 3,739 4,187 6,349 7,114 Current assets (d) 710 875 2,368 1,149 3,078 2,024 Current liabilities (111 ) (186 ) (235 ) (1,357 ) (346 ) (1,543 ) Non-current liabilities (d) (117 ) (174 ) (3,977 ) (2,244 ) (4,094 ) (2,418 ) Net assets 3,092 3,442 1,895 1,735 4,987 5,177 – attributable to non-controlling interests 1,237 1,375 - - 1,237 1,375 – attributable to Rio Tinto 1,855 2,067 1,895 1,735 3,750 3,802 Cash flow from operations 933 1,048 1,151 1,207 2,084 2,255 Dividends paid to non-controlling interests (224 ) (230 ) - - (224 ) (230 ) (c) “Other companies and eliminations” includes North Mining Limited (a wholly owned subsidiary of the Group which accounts for its interest in Robe River) and goodwill of US$351 million (2017: US$389 million) that arose on the Group’s acquisition of its interest in Robe River. (d) The 2017 comparative has been adjusted to more appropriately classify certain balances.

Principal joint operations

Principal joint operations	12 Months Ended
	Dec. 31, 2018
Disclosure Of Joint Operations [Abstract]
Principal joint operations	At 31 December 201 Company and country of incorporation/operation Principal activities Group interest (%) Australia Tomago Aluminium Joint Venture Aluminium smelting 51.6 Gladstone Power Station Power generation 42.1 Hope Downs Joint Venture Iron ore mining 50 Queensland Alumina Limited (a) (b) Alumina production 80 Pilbara Iron arrangement Infrastructure, corporate and mining services (c) New Zealand New Zealand Aluminium Smelters Limited (a) (b) Aluminium smelting 79.36 Canada Aluminerie Alouette Inc. Aluminium production 40 US Pechiney Reynolds Quebec Inc (b) (d) Aluminium smelting 50.2 This list includes only those joint operations that have a more significant impact on the profit or operating assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s joint operations are held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) Although the Group has a 79.4% interest in New Zealand Aluminium Smelters Limited and an 80% interest in Queensland Alumina Limited, decisions about activities that significantly affect the returns that are generated require agreement of both parties to the arrangements, giving rise to joint control. (b) Queensland Alumina Limited, New Zealand Aluminium Smelters Limited and Pechiney Reynolds Quebec Inc. are joint arrangements that are primarily designed for the provision of output to the parties sharing joint control; this indicates that the parties have rights to substantially all the economic benefits of the assets. The liabilities of the arrangements are in substance satisfied by cash flows received from the parties; this dependence indicates that the parties in effect have obligations for the liabilities. It is these facts and circumstances that give rise to the classification of these entities as joint operations. (c) A number of arrangements are in place between the Australian Iron Ore operations managed by Rio Tinto which allow their respective assets to be operated as a single integrated network across the Pilbara region. The arrangements are managed through two wholly owned subsidiaries: Pilbara Iron (Company) Services Pty Ltd and Pilbara Iron Pty Ltd. In assessing the Pilbara Iron arrangements, it has been concluded that they collectively constitute a joint operation on the basis that decisions about relevant activities require unanimous consent. The resulting efficiencies are shared between Rio Tinto and Robe River Iron Associates (Robe River), and the parties fund all of the cash flow requirements of Pilbara Iron (Company) Services Pty Ltd and Pilbara Iron Pty Ltd. (d) Pechiney Reynolds Quebec Inc. has a 50.1% interest in the Aluminerie de Bécancour, Inc. aluminium smelter, which is located in Canada.

Principal joint ventures

Principal joint ventures	12 Months Ended
	Dec. 31, 2018
Disclosure Of Joint Ventures [Abstract]
Principal joint ventures	At 31 December 201 Company and country of incorporation/operation Principal activities Number of Class of Proportion Group Chile Minera Escondida Limitada (a) Copper mining and refining - - - 30 Oman Sohar Aluminium Co. L.L.C. (b) Aluminium smelting; power generation 37,500 Ordinary 20 20 This list includes only those joint ventures that have a more significant impact on the profit or operating assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s principal joint ventures are held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) Although the Group has a 30% interest in Minera Escondida Limitada, participant and management agreements provide for an Owners’ Council whereby significant commercial and operational decisions about the relevant activities that significantly affect the returns that are generated in effect require the joint approval of both Rio Tinto and BHP Billiton (holders of a 57.5% interest). It is therefore determined that Rio Tinto has joint control. The year end of Minera Escondida Limitada is 30 June. The amounts included in the consolidated financial statements of Rio Tinto are, however, based on accounts of Minera Escondida Limitada that are coterminous with those of the Group. (b) Although the Group holds a 20% interest in Sohar Aluminium Co. L.L.C., decisions about relevant activities that significantly affect the returns that are generated require agreement of all parties to the arrangement. It is therefore determined that Rio Tinto has joint control. Summary information for joint ventures that are material to the Group This summarised financial information is shown on a 100% basis. It represents the amounts shown in the joint ventures’ financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments and amounts due to and from Rio Tinto. Minera Minera Sohar Sohar Escondida Escondida Aluminium Aluminium Limitada (a) Limitada (a) Co. L.L.C. (b) Co. L.L.C. (b) 2018 2017 2018 2017 US$m US$m US$m US$m Revenue 7,580 6,037 810 460 Depreciation and amortisation (1,727 ) (1,690 ) (120 ) (145 ) Other operating costs (3,230 ) (2,617 ) (440 ) (205 ) Operating profit 2,623 1,730 250 110 Finance expense (163 ) (120 ) (35 ) (35 ) Income tax (873 ) (627 ) (40 ) - Profit after tax 1,587 983 175 75 Total comprehensive income 1,587 983 175 75 Non-current assets 13,027 13,814 3,085 3,230 Current assets 2,413 2,760 340 305 Current liabilities (1,637 ) (1,727 ) (230 ) (205 ) Non-current liabilities (4,460 ) (4,617 ) (955 ) (1,270 ) Net assets 9,343 10,230 2,240 2,060 Assets and liabilities above include: – c ash and cash equivalents 697 460 15 95 – current financial liabilities (230 ) (330 ) (100 ) (130 ) – non-current financial liabilities (2,763 ) (2,840 ) (795 ) (1,120 ) Dividends received from joint venture (Rio Tinto share) 786 780 - - Reconciliation of the above amounts to the investment recognised in the Group balance sheet Group interest 30 % 30 % 20 % 20 % Net assets 9,343 10,230 2,240 2,060 Group's ownership interest 2,803 3,069 448 412 Other adjustments - 4 (1 ) (3 ) Carrying value of Group's interest 2,803 3,073 447 409 (a) In addition to its “Investment in equity accounted units”, the Group recognises deferred tax liabilities of US$413 million (2017: US$500 million) relating to tax on unremitted earnings of equity accounted units. (b) Under covenants stipulated in the agreement to Sohar Aluminium Co. L.L.C.’s secured loan facilities, Sohar Aluminium Co. L.L.C. is currently restricted from making any shareholder distributions until 2021 unless a specified amount of the loan facilities is funded.

Principal associates

Principal associates	12 Months Ended
	Dec. 31, 2018
Disclosure Of Significant Investments In Associates [Abstract]
Principal associates	Notes to the 2018 financial statements continued At 31 December 201 Company and country of incorporation/operation Principal activities Number of shares held Class of shares held Proportion of class held (%) Group interest (%) Australia Boyne Smelters Limited (a) Aluminium smelting 153,679,560 Ordinary 59.4 59.4 Brazil Mineração Rio do Norte S.A. (b) Bauxite mining 25,000,000,000 Ordinary 12.5 12 47,000,000,000 Preferred 11.75 US Halco (Mining) Inc. (c) 4,500 Common 45 45 This list includes only those associates that have a more significant impact on the profit or operating assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s principal associates are held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) The parties that collectively control Boyne Smelters Limited do so through decisions that are determined on an aggregate voting interest that can be achieved by several combinations of the parties. Although each combination requires Rio Tinto’s approval, this is not joint control as defined under IFRS 11. Rio Tinto is therefore determined to have significant influence over this company. (b) Although the Group holds only 12% of Mineração Rio do Norte S.A., it has representation on its board of directors and a consequent ability to participate in the financial and operating policy decisions. It is therefore determined that Rio Tinto has significant influence. (c) Halco (Mining) Inc. has a 51% indirect interest in Compagnie des Bauxites de Guinée, a bauxite mine, the core assets of which are located in Guinea. Summary information for associates that are material to the Group This summarised financial information is shown on a 100% basis. It represents the amounts shown in the associate’s financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments and amounts due to and from Rio Tinto. Boyne Boyne Smelters Smelters Limited (a) Limited (a) 2018 2017 US$m US$m Revenue - - (Loss)/profit after tax (12 ) 5 Other comprehensive (loss)/income (b) (68 ) 56 Total comprehensive (loss)/income (80 ) 61 Non-current assets 1,268 1,468 Current assets 93 88 Current liabilities (113 ) (99 ) Non-current liabilities (842 ) (996 ) Net assets 406 461 Reconciliation of the above amounts to the investment recognised in the Group balance sheet Group interest 59.4 % 59.4 % Net assets 406 461 Group's ownership interest 241 274 Loans to equity accounted units 129 159 Carrying value of Group's interest 370 433 (a) Boyne Smelters Limited is a tolling operation; as such it is dependent on its participants for funding which is provided through cash calls. Rio Tinto has made certain prepayments to Boyne for toll processing of alumina. These are charged to Group operating costs as processing takes place. (b) “Other comprehensive (loss)/income” is net of amounts recognised by subsidiaries in relation to quasi equity loans. Summary information for joint ventures and associates that are not individually material to the Group Joint Joint ventures ventures Associates Associates 2018 2017 2018 2017 US$m US$m US$m US$m Carrying value of Group's interest - - 679 571 Profit after tax - - 9 25 Other comprehensive income - - (23 ) 14 Total comprehensive income - - (14 ) 39

Purchases and sales of subsidia

Purchases and sales of subsidiaries, joint ventures, associates and other interests in businesses	12 Months Ended
	Dec. 31, 2018
Disclosure Of Purchases And Sales Of Subsidiaries Joint Ventures Associates And Other Interests In Businesses [Abstract]
Purchases and sales of subsidiaries, joint ventures, associates and other interests in businesses	Acquisitions Over the past three years, we have made no material acquisitions. However, on 10 May 2018 we created a joint venture, Elysis, with Alcoa and other partners to develop and commercialise a carbon-free aluminium smelting process. We are treating this as an acquisition for accounting purposes. We have accounted for our interest in Elysis using the equity method, with the initial purchase price allocation based on an independent valuation. We invested cash of US$5 million and contributed patents and licensed intellectual property (IP) to the venture. The patents and IP had no carrying value; however, on formation of the arrangement, they were recorded at fair value to reflect the contributions of the other parties in the joint venture. This value was US$171 million (US$141 million after tax). Also, in May 2017, our subsidiary, Simfer Jersey Limited (Rio Tinto share: 53%) purchased a 4.25% interest in Simfer S.A. from International Finance Corporation (IFC) for US$194 million in accordance with a put option exercised by IFC. As a result, we increased our effective share of Simfer S.A. from 42.80% to 45.05%. 2018 disposals On 1 June 2018, we disposed of our entire 75% interest in the Winchester South coal development project in Queensland, Australia to Whitehaven Coal Limited for US$200 million. This comprised US$150 million cash which was received in the year and recognised within “net cash generated from operating activities” within the cash flow statement and an unconditional cash payment of US$50 million due in June 2019. A gain on disposal of US$195 million was recognised within “profit relating to interests in undeveloped projects” in the income statement. On 1 August 2018, we completed the sale of our entire interest in the Hail Creek coal mine (82.0%) and the Valeria coal development project (71.2%) in Queensland, Australia to Glencore for a total consideration of US$1.7 billion. We received net proceeds of US$1,545 million after completion adjustments in respect of the Hail Creek component of this transaction, resulting in a pre-tax gain of US$1,141 million. We also received cash proceeds of US$170 million in respect of Valeria. Of this amount, US$87 million relating to the sale of land and investments in associates was included in investing cash flow, resulting in a pre-tax gain of US$18 million. The remaining US$83 million proceeds were recognised in operating cash flow, resulting in a pre-tax gain of US$83 million in “profit relating to interests in undeveloped prohects”. Also on 1 August 2018, we completed the sale of our entire interest in the Kestrel underground coal mine (80.0%) for US$2.25 billion to a consortium comprising EMR On 14 December 2018, we completed the sale of the Dunkerque aluminium smelter in northern France to Liberty House for US$500 million. In 2018 we received net cash proceeds of US$385 million after adjustments and expect to receive a further US$52 million in 2019. We recognised a pre-tax gain on disposal of US$128 million. On 21 December 2018, we sold our interest in the Grasberg mine for US$3.5 billion as part of a series of transactions involving Inalum (PT Indonesia Asahan Aluminium (Persero)) and Freeport McMoRan Inc. Of the US$3.5 billion received, US$107 million relates to our attributable share of copper and gold revenues for 2018, net of our capital contribution for the year. The remaining net proceeds of US$3,392 million were included in investing cash flow and gave rise to a gain on disposal of US$2,146 million. 2017 disposals On 1 September 2017, we disposed of our 100% shareholding in Coal & Allied Industries Limited to Yancoal Australia Limited for a total consideration of US$2.69 billion (before working capital adjustments). This comprises US$2.45 billion in cash paid on the closing date and a further US$240 million of unconditional guaranteed royalty payments. During 2017, we received US$110 million; total net cash proceeds received in 2017, net of working capital adjustments, transaction costs and cash transferred, were US$2.54 billion. We received a further US$90 million of unconditional guaranteed royalty payments in 2018 and expect to receive the remaining US$40 million between 2019 and 2021. 2016 disposals On 1 March 2016, we disposed of our 40% interest in the Bengalla Joint Venture to New Hope Corporation Limited for US$617 million (before finalisation of net debt and working capital adjustments). On 31 March 2016, we disposed of our 100% interest in Carbone Savoie to Alandia Industries. We transferred our 53.83% shareholding in Bougainville Copper Limited (BCL) to Equity Trustees Limited (independent trustee) on 30 June 2016 for US$nil consideration. Equity Trustees Limited subsequently distributed the shares in accordance with the trust deed to nominees of each of the Autonomous Bougainville Government (36.4%) and the Independent State of Papua New Guinea (17.4%) such that each party now controls an equal share of BCL (36.4%). We did not previously consolidate BCL because we determined that, in accordance with IFRS as defined in note 1, the Group does not control the relevant activities, as the mining of copper at the Panguna mine was halted by militant activity in 1989. The carrying value had previously been fully impaired and therefore the transfer resulted in no financial impact for the year ended 31 December 2016. On 20 July 2016, a tranche of 7.5% non-contributory shares in Simfer S.A. was transferred free of charge to the Government of Guinea as per the terms of the Simandou project agreement signed in 2014, further diluting our ownership percentage and also our partners’ in the project. Under the agreement, a second tranche comprising 10% Ordinary Contributory Shares may be acquired at any time for a pro rata share of historical mining cost. The remaining two tranches of 5% ordinary contributing shares may be acquired by the Government of Guinea at market value at any time after 22 April 2026 and 22 April 2031 respectively. On 2 September 2016, we disposed of our interest in Zululand Anthracite Colliery. On 23 November 2016, we disposed of our 100% interest in Lochaber to SIMEC for US$410 million (before finalisation of closing adjustments and transaction costs). We received US$224 million of this in December 2016 and the second and final instalment in April 2017.

Directors' and key management r

Directors' and key management remuneration	12 Months Ended
	Dec. 31, 2018
Disclosure Of Information About Key Management Personnel [Abstract]
Directors' and key management remuneration	Aggregate remuneration, calculated in accordance with the UK Companies Act 2006, of the directors of the parent companies was as follows: 2018 US$’000 2017 US$’000 2016 US$’000 Emoluments 9,069 8,339 9,186 Long term incentive plans 2,923 4,685 3,071 11,992 13,024 12,257 Pension contributions: defined contribution plans 80 135 69 Gains made on exercise of share options 107 - - The Group defines key management personnel as the directors and members of the Executive Committee. The Executive Committee comprises the executive directors, product group chief executive officers and Group executives. The aggregate remuneration incurred by Rio Tinto plc in respect of its directors was US$11,465,000 (2017: US$12,624,000; 2016: US$10,630,000). The aggregate pension contribution to defined contribution plans was US$80,000 (2017: US$135,000; 2016: US$69,000). The aggregate remuneration, including pension contributions and other retirement benefits, incurred by Rio Tinto Limited in respect of its directors was US$607,000 (2017: US$535,000; 2016: US$1,696,000). The aggregate pension contribution to defined contribution plans was US$nil (2017: US$nil; 2016: US$nil). During 2018, no directors (2017: nil; 2016: one) accrued retirement benefits under defined benefit arrangements, and three directors (2017: two; 2016: two) accrued retirement benefits under defined contribution arrangements. Emoluments included in the table above have been translated from local currency at the average exchange rate for the year with the exception of bonus payments, which have been translated at the year-end rate. Detailed information concerning directors’ remuneration, shareholdings and options is shown in the Remuneration report, including tables 1 to 3, on pages 103 to 136. Aggregate compensation, representing the expense recognised under IFRS, as defined in note 1, of the Group’s key management, including directors, was as follows: 2018 US$’000 2017 US$’000 2016 US$’000 Short-term employee benefits and costs 23,978 23,095 22,269 Post-employment benefits 629 415 3,461 Employment termination benefits 69 - 2,682 Share-based payments 14,916 8,033 15,806 Total 39,592 31,543 44,218 The figures shown above include employment costs which comprise social security and accident premiums in Canada, the UK and US and payroll taxes in Australia paid by the employer as a direct additional cost of hire. In total, they amount to US$2,360,000 (2017: US$2,122,000; 2016: US$2,295,000) and although disclosed here, are not included in table 1 of the Remuneration report. More detailed information concerning the remuneration of key management is shown in the Remuneration report, including tables 1 to 3 on pages 103 to 136.

Auditors' remuneration

Auditors' remuneration	12 Months Ended
	Dec. 31, 2018
Auditors Remuneration [Abstract]
Auditors' remuneration	2018 US$m 2017 US$m 2016 US$m Group Auditors’ remuneration (a) Audit of the Group 9.2 6.2 4.5 Audit of subsidiaries 7.5 8.1 9.0 Total audit 16.7 14.3 13.5 Audit-related assurance service 0.9 1.0 0.9 Other assurance services (b) 3.3 2.3 0.6 Total assurance services 4.2 3.3 1.5 Tax compliance (c) - 0.3 0.5 Tax advisory services (c) - 0.2 0.1 Other non-audit services not covered above 0.2 0.7 1.8 Total non-audit services 4.4 4.5 3.9 Total Group Auditors’ remuneration 21.1 18.8 17.4 Audit fees payable to other accounting firms Audit of the financial statements of the Group’s subsidiaries 1.4 2.0 2.1 Fees in respect of pension scheme audits 0.1 0.5 0.3 Total audit fees payable to other accounting firms 1.5 2.5 2.4 (a) The remuneration payable to PwC, the Group Auditors, is approved by the Audit Committee. The Committee sets the policy for the award of non-audit work to the auditors and approves the nature and extent of such work, and the amount of the related fees, to ensure that independence is maintained. The fees disclosed above consolidate all payments made to member firms of PwC by the companies and their subsidiaries, along with fees in respect of joint operations paid for by the Group. Non-audit services arise largely from assurance and/or regulation related work. Also included in amounts above are US$0.1 million for audits relating to associated pension schemes of the company and US$0.1 million of non-audit services relating to associated pension schemes. (b) Other assurance services relates to the review of non-statutory financial information including sustainability reporting. (c) Tax compliance and tax advisory services incurred in the year amounted to US$0.04 million.

Related-party transactions

Related-party transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related-party transactions	Information about material related-party transactions of the Rio Tinto Group is set out below. Subsidiary companies and joint operations Details of investments in principal subsidiary companies are disclosed in note 33. Information relating to joint operations can be found in note 34. Equity accounted units Transactions and balances with equity accounted units are summarised below. Purchases, trade and other receivables, and trade and other payables relate largely to amounts charged by equity accounted units for toll processing of alumina and purchasing of bauxite and aluminium. Sales relate largely to sales of alumina to equity accounted units for smelting into aluminium. 2018 2017 2016 Income statement items Note US$m US$m US$m Purchases from equity accounted units (1,209 ) (993 ) (1,216 ) Sales to equity accounted units 493 210 248 Cash flow statement items US$m US$m US$m Dividends from equity accounted units 800 817 253 Net funding of equity accounted units (9 ) (3 ) (12 ) Balance sheet items US$m US$m US$m Investments in equity accounted units (a) 15 4,299 4,486 5,019 Loans to equity accounted units 20 38 39 39 Loans from equity accounted units 22 - (31 ) (49 ) Trade and other receivables: amounts due from equity accounted units (b) 18 278 299 298 Trade and other payables: amounts due to equity accounted units 25 (223 ) (175 ) (243 ) (a) Investments in equity accounted units include quasi equity loans. Further information about investments in equity accounted units is set out in notes 35 and 36. (b) This includes prepayments of tolling charges. Pension funds Information relating to pension fund arrangements is set out in note 44. Directors and key management Details of directors’ and key management’s remuneration are set out in note 38 and in the Remuneration report on pages 103 to 136.

Exchange rates in US$

Exchange rates in US$	12 Months Ended
	Dec. 31, 2018
Foreign Exchange Rates [Abstract]
Exchange rates in US$	The principal exchange rates used in the preparation of the 2018 financial statements were: Full-year average Year-end 2018 2017 2016 2018 2017 2016 Sterling 1.34 1.29 1.36 1.27 1.34 1.22 Australian dollar 0.75 0.77 0.74 0.70 0.78 0.72 Canadian dollar 0.77 0.77 0.76 0.73 0.79 0.74 Euro 1.18 1.13 1.11 1.14 1.20 1.05 South African rand 0.076 0.075 0.068 0.069 0.081 0.073

Events after the balance sheet

Events after the balance sheet date	12 Months Ended
	Dec. 31, 2018
Disclosure Of Nonadjusting Events After Reporting Period [Abstract]
Events after the balance sheet date	There were no significant events identified after the balance sheet date that are required to be disclosed.

Share-based payments

Share-based payments	12 Months Ended
	Dec. 31, 2018
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Abstract]
Share-based payments	Rio Tinto plc and Rio Tinto Limited have a number of share-based incentive plans, which are described in detail in the Remuneration report. These plans have been accounted for in accordance with the fair value recognition provisions of IFRS 2 “Share-based Payment”. The charge that has been recognised in the income statement for Rio Tinto’s share-based incentive plans, and the related liability (for cash-settled plans), is set out in the table below. Charge recognised for the year Liability at the end of the year 2018 2017 2016 2018 2017 US$m US$m US$m US$m US$m Equity-settled plans 118 88 116 - - Cash-settled plans 4 3 - 16 15 Total 122 91 116 16 15 The main Rio Tinto plc and Rio Tinto Limited plans are as follows: Share Option Plans Awards are no longer granted under the Share Option Plans and all charges have been incurred as the remaining awards all vested before 2018, although there remain outstanding vested options under these plans, all of which are due to expire in 2019. UK Share Plan (formerly the Share Ownership Plan) The fair values of Matching and Free Shares made by Rio Tinto plc are taken to be the market value of the shares on the date of purchase. These awards are settled in equity. Performance Share Plans Participants are generally assigned shares in settlement of their Performance Share Awards (PSA) on vesting and therefore the awards are accounted for in accordance with the requirements applying to equity-settled share-based payment transactions, including the dividends accumulated from date of award to vesting. For the parts of awards with Total Shareholder Return (TSR) performance conditions, the fair value of the awards was calculated using a Monte Carlo simulation model taking into account the TSR performance conditions. One-third of the awards granted from 2013 to 2017 (inclusive) are subject to an earnings margin performance target relative to ten global mining comparators. As this is a non-market related performance condition, under IFRS 2, the fair value recognised is reviewed at each accounting date based on the directors’ expectations for the proportion vesting. Forfeitures prior to vesting are assumed at 5% per annum of outstanding awards (2017: 5% per annum). Management Share Plans The Management Share Plans were introduced in 2007 (and readopted in 2017) to provide Management Share Awards (MSA) to management. The vesting of these awards is dependent on service conditions being met. In general, the awards will be settled in equity, including the dividends accumulated from date of award to vesting. The awards are accounted for in accordance with the requirements applying to equity-settled share-based payment transactions. The fair value of each award on the day of grant is equal to the share price on the day of grant less a small adjustment for the timing of dividends. For awards granted since 2017 this adjustment is negligible and therefore the fair value of each award is equal to the share price on the day of grant. Forfeitures prior to vesting are assumed at 7% per annum of outstanding awards (2017: 7% per annum). Bonus Deferral Plans The Bonus Deferral Plans were introduced to award Bonus Deferral Awards (BDA) in connection with the mandatory deferral of 50% of the bonuses for executive directors and product group executives and 25% of the bonuses for other executives. Notes to the 2018 financial statements continued 43 Share-based payments continued The vesting of these awards is dependent only on service conditions being met. In general, the awards will be settled in equity including the dividends accumulated from date of award to vesting. The awards are accounted for in accordance with the requirements applying to equity-settled share-based payment transactions. The fair value of each award on the day of grant is equal to the share price on the day of grant less a small adjustment for the timing of dividends. For awards granted since 2017 this adjustment is negligible and therefore the fair value of each award is equal to the share price on the day of grant. Equity Incentive Plan In 2018, shareholders approved the introduction of the Rio Tinto 2018 Equity Incentive Plan (the “EIP”). From 2018, all long-term incentive awards will be granted under this umbrella plan which allows for awards in the form of PSA, MSA and BDA to be granted. For grants made from 2018, the earnings margin performance target applying to the PSA was removed and instead all of the awards are subject to the TSR performance conditions described above and in the Directors’ Remuneration report. Global Employee Share Plans The Global Employee Share Plans were introduced in 2012. The companies provide a matching share award for each investment share purchased by a participant. The vesting of these matching awards is dependent on service conditions being met and the continued holding of investment shares by the participant until vesting. These awards are settled in equity Summary of options outstanding and exercisable A summary of the status of the companies’ equity-settled share option plans at 31 December 2018 is presented below. Options outstanding and exercisable at 31 December 2018 Number Weighted average exercise price per option £/A$ Weighted average remaining contractual life Years Aggregate intrinsic value 2018 US$m Rio Tinto plc Share Option Plan (exercise price £16 – £25) 23,659 17 0.22 1 Rio Tinto Limited Share Option Plan (exercise price A$33) 16,455 33 0.21 - 40,114 1 As at 31 December 2017 there were 188,766 options outstanding with an aggregate intrinsic value of US$3 million. The Management Share Plans, Performance Share Plans, Bonus Deferral Plans, Equity Incentive Plans, Global Employee Share Plans and UK Share Plan together represent 100% (2017: 100%) of the total IFRS 2 charge for Rio Tinto plc and Rio Tinto Limited plans in 2018. Performance Share Awards (granted under either the Performance Share Plans or the Equity Incentive Plans) Rio Tinto plc awards Rio Tinto Limited awards 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 Non-vested shares at 1 January 3,555,274 20.47 2,883,053 18.27 1,609,154 40.13 1,590,957 37.52 Awarded 801,047 26.87 1,198,677 24.64 387,298 53.85 529,776 45.84 Forfeited (188,761) 21.45 (199,435) 16.28 (36,530) 43.83 (36,716) 36.59 Failed performance conditions (107,625) 14.54 (161,966) 16.25 (54,322) 27.67 (113,857) 30.89 Vested (214,853) 21.57 (165,055) 21.51 (108,321) 40.85 (84,284) 40.79 Transfers from equity to cash-settled (a) - - - - - - (276,722) 40.11 Non-vested shares at 31 December 3,845,082 21.86 3,555,274 20.47 1,797,279 43.34 1,609,154 40.13 2018 number Weighted average share price 2018 2017 number Weighted average share price 2017 2018 number Weighted average share price 2018 2017 number Weighted average share price 2017 Vested awards settled in shares during the year (including dividend shares applied on vesting) 248,965 42.57 188,383 31.04 105,374 82.97 73,311 63.09 Vested awards settled in cash during the year (including dividend shares applied on vesting) 991 42.40 - - 9,959 82.08 5,010 62.81 (a) In 2017, an agreement was reached between the Group and a former director to settle any of his future vested awards in cash rather than equity. In addition to the equity-settled awards shown above, there were 40,365 Notes to the 2018 financial statements continued 43 Share-based payments continued Management Share Awards, Bonus Deferral Awards (granted under the Management Share Plans, Bonus Deferral Plans or Equity Incentive Plans), Global Employee Share Plans and UK Share Plan (combined) Rio Tinto plc awards (a) Rio Tinto Limited awards 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 Non-vested awards at 1 January 3,473,092 27.23 3,305,966 26.00 2,933,237 54.15 2,986,080 53.32 Awarded 1,135,103 39.49 1,499,374 32.50 943,315 78.36 1,156,078 61.05 Forfeited (250,853) 30.26 (159,669) 29.46 (185,062) 64.60 (127,905) 53.61 Cancelled (33,563) 26.52 (51,773) 25.82 (36,613) 52.84 (95,203) 51.18 Vested (1,281,759) 27.54 (1,120,806) 30.41 (1,040,947) 55.30 (985,813) 60.06 Non-vested shares at 31 December 3,042,020 31.43 3,473,092 27.23 2,613,930 61.71 2,933,237 54.15 Comprising: – Management Share Awards 1,666,082 32.52 1,897,318 27.99 1,520,292 64.06 1,617,838 55.42 – Bonus Deferral Awards 203,900 37.86 281,994 25.53 127,423 71.93 153,966 52.83 – Global Employee Share Plan 1,102,322 28.68 1,196,937 26.42 966,215 56.66 1,161,433 52.54 – UK Share Plan 69,716 29.90 96,843 27.14 - - - - 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 Vested awards settled in shares during the year (including dividend shares applied on vesting): – Management Share Awards 669,678 40.03 653,776 35.33 570,173 80.87 577,083 67.93 – Bonus Deferral Awards 221,198 37.69 170,036 34.44 108,001 75.36 88,644 69.98 – Global Employee Share Plan 451,710 39.06 382,585 33.56 473,420 78.78 466,308 65.10 – UK Share Plan 16,968 38.21 11,120 34.56 - - - - (a) Awards of Rio Tinto American Depository Receipts (ADRs) under the Global Employee Share Plan are included within the totals for Rio Tinto plc awards for the purpose of these tables. In addition to the equity-settled awards shown above, there were 46,543 Rio Tinto plc and 83,092 Rio Tinto Limited cash-settled awards outstanding at 31 December 2018 (2017: 33,443 Rio Tinto plc and 87,019 Rio Tinto Limited cash-settled awards outstanding). The total liability for these awards at 31 December 2018 was US$5 million (2017: US$6 million).

Post-retirement benefits

Post-retirement benefits	12 Months Ended
	Dec. 31, 2018
Disclosure Of Pension And Post Retirement Healthcare Plans [Abstract]
Post-retirement benefits	Description of plans The Group operates a number of pension and post-retirement healthcare plans around the world. Some of these plans are defined contribution and some are defined benefit, with assets held in separate trusts, foundations and similar entities. Defined benefit pension and post-retirement healthcare plans expose the Group to a number of risks: Uncertainty in benefit payments The value of the Group’s liabilities for post-retirement benefits will ultimately depend on the amount of benefits paid out. This in turn will depend on the level of future pay increases, the level of inflation (for those benefits that are subject to some form of inflation protection) and how long individuals live. Volatility in asset values The Group is exposed to future movements in the values of assets held in pension plans to meet future benefit payments. Uncertainty in cash funding Movements in the values of the obligations or assets may result in the Group being required to provide higher levels of cash funding, although changes in the level of cash required can often be spread over a number of years. In some countries control over the rate of cash funding or over the investment policy for pension assets might rest to some extent with a trustee body or other body that is not under the Group’s direct control. In addition the Group is also exposed to adverse changes in pension regulation. For these reasons the Group has a policy of moving away from defined benefit pension provisions and towards defined contribution arrangements instead. The defined benefit pension plans for salaried employees are closed to new entrants in almost all countries. For unionised employees, some plans remain open. The Group does not usually participate in multi-employer plans in which the risks are shared with other companies using those plans. The Group’s participation in such plans is immaterial and consequently no detailed disclosures are provided in this note. Pension plans The majority of the Group’s defined benefit pension obligations are in Canada, the UK, the US and Switzerland. In Canada the benefits for salaried staff are generally linked to final average pay and the plans are generally closed to new entrants. Benefits for bargaining employees are reviewed in negotiation with unions and are typically either linked to final average pay or to a flat monetary amount per year of service. New employees join arrangements which are defined contribution from the Group’s perspective, with any required additional funding being provided by employees. The plans are subject to the regulatory requirements that apply to Canadian pension plans in the relevant provinces and territories (predominantly Quebec). Pension Committees are responsible for ensuring that the plans operate in a manner that is compliant with the relevant regulations. The Pension Committees generally have a number of members appointed by the sponsor and a number appointed by the plan participants. In some cases there is also an independent Committee member. The defined benefit sections of the UK arrangements are linked to final pay. New employees are admitted to defined contribution sections. The plans are subject to the regulatory requirements that apply to UK pension plans. Trustees are responsible for ensuring that the plans operate in a manner that is compliant with UK regulations. The trustee board governing the main UK plans has a number of directors appointed by the sponsor, a number appointed by the plan participants and an independent trustee director. A number of defined benefit pension plans are sponsored by the US entities. Benefits for salaried staff are generally linked to final average pay and the plans are closed to new entrants. Benefits for bargaining employees are reviewed in negotiation with unions and are typically a flat monetary amount per year of service. New employees are admitted to defined contribution plans. A Benefits Governance Committee is responsible for ensuring that the plans are compliant with US regulations. Members of that Committee are appointed by the sponsor. In Europe, there are defined benefit plans in Switzerland, Germany and France. The largest single plan is in Switzerland and provides benefits linked to final average pay. The Swiss plan is overseen by a foundation board which is responsible for ensuring that the plan complies with Swiss regulations. Foundation board members are appointed by the plan sponsor, by employees and by retirees. In Australia, the main arrangements are principally defined contribution in nature but there are sections providing defined benefits linked to final pay, typically paid in lump sum form. The Group also operates a number of unfunded defined benefit plans, which are included in the figures below. Post-retirement healthcare plans Certain subsidiaries of the Group, mainly in the US and Canada, provide health and life insurance benefits to retired employees and in some cases to their beneficiaries and covered dependants. Eligibility for cover is dependent upon certain age and service criteria. These arrangements are generally unfunded, and are included in the figures below. Plan assets The assets of the pension plans are invested predominantly in a diversified range of equities, bonds and property. Consequently, the funding level of the pension plans is affected by movements in the level of equity markets and also by movements in interest rates. The Group monitors its exposure to changes in interest rates and equity markets and also measures its balance sheet pension risk using a value at risk approach. These measures are considered when deciding whether significant changes in investment strategy are required. Asset-liability studies are conducted on a periodic basis for the main pension plans to determine the optimal investment mix bearing in mind the Group’s tolerance for risk, the risk tolerance of the local sponsor companies and the views of the Pension Committees and trustee boards who are legally responsible for the investments of the plans. In Canada, the UK and Switzerland, the Group works with the governing bodies to ensure that the investment policy adopted is consistent with the Group’s tolerance for risk. In the US the Group has direct control over the investment policy, subject to local investment regulations. The proportions of the total fair value of assets in the pension plans for each asset class at the balance sheet date were: 2018 2017 Equities 20.7% 32.4% – Quoted 16.7% 28.6% – Private 4.0% 3.8% Bonds 63.6% 53.2% – Government fixed income 18.0% 14.3% – Government inflation-linked 15.5% 13.1% – Corporate and other publicly quoted 27.1% 23.5% – Private 3.0% 2.3% Property 11.0% 11.2% – Quoted property funds 5.1% 5.8% – Unquoted property funds 5.9% 5.4% Qualifying insurance policies 0.1% 0.2% Cash and other 4.6% 3.0% Total 100.0% 100.0% The assets of the plans are managed on a day-to-day basis by external specialist fund managers. These managers may invest in the Group’s securities subject to limits imposed by the relevant fiduciary committees and local legislation. The approximate total holding of Group securities within the plans is US$3 million (2017: US$13 million). The holdings of quoted equities are invested either in pooled funds or segregated accounts held in the name of the relevant pension funds. These equity portfolios are well diversified in terms of the geographic distribution and market sectors. The holdings of government bonds are generally invested in the debt of the country in which a pension plan is situated. Corporate and other quoted bonds are usually of investment grade. Private debt is mainly in North America. The property funds are invested in a diversified range of properties. The holdings of cash &andother are predominantly cash and short-term money market instruments. Investments in private equity, private debt and property are less liquid than the other investment classes listed above and therefore the Group’s investment in those asset classes is restricted to a level that does not endanger the liquidity of the pension plans. The Group does not currently utilise derivatives to manage risk in its pension plans. However, fund managers may use derivatives to hedge currency movements within their portfolios and, in the case of bond managers, to take positions that could be taken using direct holdings of bonds but more efficiently. Notes to the 2018 financial statements continued 44 Post-retirement benefits continued Maturity of defined benefit obligations An approximate analysis of the maturity of the obligations is given in the table below: Pension benefits Other benefits 2018 Total % 2017 Total % 2016 Total % Proportion relating to current employees 20% 15% 19% 20% 21% Proportion relating to former employees not yet retired 11% 2% 11 % 11% 12% Proportion relating to retirees 69% 83% 70 % 69% 67% Total 100% 100% 100 % 100% 100% Average duration of obligations (years) 13.4 12.7 13.4 13.9 14.3 Geographical distribution of defined benefit obligations An approximate analysis of the geographic distribution of the obligations is given in the table below: Pension benefits Other benefits 2018 Total % 2017 Total % 2016 Total % Canada 49% 39% 48 % 49% 46% UK 30% 2% 28 % 27% 27% US 11% 56% 14 % 14% 16% Switzerland 5% 0% 5 % 5% 5% Other 5% 3% 5 % 5% 6% Total 100% 100% 100 % 100% 100% Total expense recognised in the income statement Pension benefits Other benefits 2018 Total US$m 2017 Total US$m 2016 Total US$m Current employer service cost for defined benefit plans (156) (9) (165) (155) (158) Past service (cost)/income (34) (2) (36) 4 - Curtailment gains 2 - 2 1 5 Settlement gains 5 - 5 1 - Net interest on net defined benefit liability (44) (35) (79) (79) (90) Non-investment expenses paid from the plans (15) - (15) (17) (22) Total defined benefit expense (242) (46) (288) (245) (265) Current employer service cost for defined contribution and industry-wide plans (242) (2) (244) (255) (257) Total expense recognised in the income statement (484) (48) (532) (500) (522) The above expense amounts are included as an employee cost within net operating costs. No amounts have been excluded from underlying earnings in 2018, 2017 or 2016. The past service cost in 2018 relates primarily to benefit amendments in the US and also includes US$9 million to reflect the current estimate of the cost of equalising benefits in the Group’s UK schemes, in line with the requirements of the court judgment on 26 October 2018 in the case involving Lloyds Banking Group and relating to Guaranteed Minimum Pensions. The settlement gain in 2018 is the result of certain US obligations being transferred to an external insurance company. The curtailments relate primarily to headcount reductions at various operations. Total amount recognised in other comprehensive income before tax 2018 US$m 2017 US$m 2016 US$m Actuarial gains/(losses) 1,382 (855) (1,120) Return on assets (net of interest on assets) (527) 894 1,031 Gain/(loss) on application of asset ceiling 52 (33) (1) Total gain/(loss) recognised in other comprehensive income 907 6 (90) Amounts recognised in the balance sheet The following amounts were measured in accordance with IAS 19 at 31 December: Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Total fair value of plan assets 13,203 - 13,203 15,257 Present value of obligations – funded (13,482) - (13,482) (16,199) Present value of obligations – unfunded (401) (871) (1,272) (1,446) Present value of obligations – total (13,883) (871) (14,754) (17,645) Effect of asset ceiling - - - (111) Net deficit to be shown in the balance sheet (680) (871) (1,551) (2,499) Comprising: – Deficits (1,615) (871) (2,486) (3,370) – Surpluses 935 - 935 871 Net deficits on pension plans (680) - (680) (1,501) Unfunded post-retirement healthcare obligation - (871) (871) (998) The surplus amounts shown above are included in the balance sheet as Trade and other receivables. See note 18. Deficits are shown in the balance sheet within Provisions (including post-retirement benefits). See note 26. Funding policy and contributions to plans The Group reviews the funding position of its major pension plans on a regular basis and considers whether to provide funding above the minimum level required in each country. In Canada and the US the minimum level is prescribed by legislation. In the UK and Switzerland the minimum level is negotiated with the local trustee or foundation in accordance with the funding guidance issued by the local regulators. In deciding whether to provide funding above the minimum level the Group takes into account other possible uses of cash within the Group, the tax situation of the local sponsoring entity and any strategic advantage that the Group might obtain by accelerating contributions. The Group does not generally pre-fund post-retirement healthcare arrangements. Pension benefits Other benefits 2018 Total US$m 2017 Total US$m 2016 Total US$m Contributions to defined benefit plans 204 44 248 404 464 Contributions to defined contribution plans 242 2 244 243 240 Contributions to industry-wide plans - - - 12 17 Total 446 46 492 659 721 Contributions to defined benefit pension plans are kept under regular review and actual contributions will be determined in line with the Group’s wider financing strategy, taking into account relevant minimum funding requirements. As contributions to many plans are reviewed on at least an annual basis, the contributions for 2019 and subsequent years cannot be determined precisely in advance. Most of the Group’s largest pension funds are fully funded on their local funding basis and do not require long-term funding commitments at present. Contributions to defined benefit pension plans for 2019 are estimated to be around US$260 million but may be higher or lower than this depending on the evolution of financial markets and voluntary funding decisions taken by the Group. Contributions for subsequent years are expected to be at similar levels to 2018. Healthcare plans are generally unfunded and contributions for future years will be equal to benefit payments net of participant contributions. The Group’s contributions in 2019 are expected to be similar to the amounts paid in 2018. Movements in the net defined benefit liability A summary of the movement in the net defined benefit liability is shown in the first table below. The subsequent tables provide a more detailed analysis of the movements in the present value of the obligations, the fair value of assets and the effect of the asset ceiling. The amounts shown below include, where appropriate, 100% of the costs, contributions, gains and losses in respect of employees who participate in the plans and who are employed in associates and joint arrangements. Consequently, the costs, contributions, gains and losses may not correspond directly to the amounts disclosed above in respect of the Group. Defined contribution plans and industry-wide plans are excluded from the movements below. Notes to the 2018 financial statements continued 44 Post-retirement benefits continued Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in the net defined benefit liability Net defined benefit liability at the start of the year (1,501) (998) (2,499) (2,542) Amounts recognised in Income statement (242) (46) (288) (245) Amounts recognised in Other comprehensive income 812 95 907 6 Employer contributions 204 44 248 404 Arrangements divested (10) - (10) 13 Currency exchange rate loss 57 34 91 (135) Net defined benefit liability at the end of the year (680) (871) (1,551) (2,499) Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in present value of obligation Present value of obligation at the start of the year (16,647) (998) (17,645) (16,228) Current employer service costs (156) (9) (165) (155) Past service (cost)/income (34) (2) (36) 4 Curtailments 2 - 2 1 Settlements 299 - 299 307 Interest on obligation (468) (35) (503) (532) Contributions by plan participants (24) - (24) (23) Benefits paid 871 44 915 949 Experience gains 11 21 32 7 Changes in financial assumptions gain/(loss) 1,276 73 1,349 (718) Changes in demographic assumptions gain/(loss) - 1 1 (144) Arrangements divested 94 - 94 13 Currency exchange rate gain/(loss) 893 34 927 (1,126) Present value of obligation at the end of the year (13,883) (871) (14,754) (17,645) Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in plan assets Fair value of plan assets at the start of the year 15,257 - 15,257 13,749 Settlements (294) - (294) (306) Interest on assets 434 - 434 459 Contributions by plan participants 24 - 24 23 Contributions by employer 204 44 248 404 Benefits paid (871) (44) (915) (949) Non-investment expenses (15) - (15) (17) Return on plan assets (net of interest on assets) (527) - (527) 894 Arrangements divested (161) - (161) - Currency exchange rate (loss)/gain (848) - (848) 1,000 Fair value of plan assets at the end of the year 13,203 - 13,203 15,257 Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in the effect of the asset ceiling Effect of the asset ceiling at the start of the year (111) - (111) (63) Interest on the effect of the asset ceiling (10) - (10) (6) Movement in the effect of the asset ceiling 52 - 52 (33) Arrangements divested and other transfers 57 - 57 - Currency exchange rate gain/(loss) 12 - 12 (9) Effect of the asset ceiling at the end of the year - - - (111) Most of the settlement amounts shown above relate to the US, where assets and obligations for some pensions in payment were transferred to an insurance company. In determining the extent to which the asset ceiling has an effect, the Group considers the funding legislation in each country and the rules specific to each pension plan. The calculation takes into account any minimum funding requirements that may be applicable to the plan, whether any reduction in future Group contributions is available, and whether a refund of surplus may be available. In considering whether any refund of surplus is available the Group considers the powers of trustee boards and similar bodies to augment benefits or wind up a plan. Where such powers are unilateral, the Group does not consider a refund to be available at the end of the life of a plan. Where the plan rules and legislation both permit the employer to take a refund of surplus, the asset ceiling may have no effect, although it may be the case that a refund will only be available many years in the future. Main assumptions (rates per annum) The main assumptions for the valuations of the plans under IAS 19 are set out below. Canada UK US Switzerland At 31 December 2018 Discount rate 3.9% 2.8% 4.2% 0.7% Inflation (a) 1.6% 3.3% 2.0% 1.2% Rate of increase in pensions 0.2% 2.9% 0.0% 0.0% Rate of increase in salaries 2.9% 3.7% 3.5% 2.2% At 31 December 2017 Discount rate 3.4% 2.3% 3.5% 0.5% Inflation (a) 1.8% 3.2% 2.1% 1.2% Rate of increase in pensions 0.5% 2.8% 0.0% 0.4% Rate of increase in salaries 3.1% 3.6% 3.6% 2.2% (a) The inflation assumption shown for the UK is for the Retail Price Index. The assumption for the Consumer Price Index at 31 December 2018 was 2.2% (2017: 2.1%). The main financial assumptions used for the healthcare plans, which are predominantly in the US and Canada, were: discount rate: 4.2% (2017: 3.6%); medical trend rate: 7.6% reducing to 4.6% by the year 2029 broadly on a straight line basis (2017: 9.8%, reducing to 4.7% by the year 2026); claims costs based on individual company experience. For both the pension and healthcare arrangements the post-retirement mortality assumptions allow for future improvements in longevity. The mortality tables used imply that a man aged 60 at the balance sheet date has a weighted average expected future lifetime of 27 years (2017: 27 years) and that a man aged 60 in 2038 would have a weighted average expected future lifetime of 28 years (2017: 28 years). Sensitivity The values reported for the defined benefit obligations are sensitive to the actuarial assumptions used for projecting future benefit payments and discounting those payments. In order to estimate the sensitivity of the obligations to changes in assumptions, we calculate what the obligations would be if we were to make changes to each of the key assumptions in isolation. The difference between this figure and the figure calculated using our stated assumptions is an indication of the sensitivity to changes in each assumption. The results of this sensitivity analysis are summarised in the table below. Note that this approach is valid for small changes in the assumptions but will be less accurate for larger changes in the assumptions. The sensitivity to inflation includes the impact on pension increases, which are generally linked to inflation where they are granted. 2018 2017 Approximate Approximate Assumption Change in assumption Pensions US$m Other US$m Pensions US$m Other US$m Discount rate Increase of 0.5 percentage points 782 51 1,091 59 Decrease of 0.5 percentage points (832) (55) (1,169) (63) Inflation Increase of 0.5 percentage points (389) (17) (579) (20) Decrease of 0.5 percentage points 369 15 550 18 Salary increases Increase of 0.5 percentage points (46) (1) (74) (1) Decrease of 0.5 percentage points 45 1 72 1 Demographic – allowance for future improvements in longevity Participants assumed to have the mortality rates of individuals who are one year older 381 18 509 20 Participants assumed to have the mortality rates of individuals who are one year younger (381) (18) (509) (20)

New standards and interpretatio

New standards and interpretations adopted in the current year	12 Months Ended
	Dec. 31, 2018
Description Of Expected Impact Of Initial Application Of New Standards Or Interpretations [Abstract]
New standards and interpretations adopted in the current year	This note explains the impact of the adoption of IFRS 9 “Financial Instruments” and IFRS 15 “Revenue from Contracts with Customers” on the Group’s financial statements. The new accounting policies applied from 1 January 2018 are set out in note 1. Prior period accounting policies are set out below. The adoption of IFRIC 22 “Foreign Currency Transactions and Advance Consideration” and other minor changes to IFRS applicable for 2018 did not have a significant impact on the Group’s financial statements. The impact on equity attributable to owners of Rio Tinto as at 1 January 2018 of the adoption of IFRS 9 and IFRS 15 is as follows: US$m Equity attributable to owners of Rio Tinto as at 31 December 2017 44,711 IFRS 9 Impairment provision resulting from application of the Expected Credit Loss (ECL) model and revaluations (5) IFRS 15 De-recognition of receivable arising from “uplift” transaction (see page 222) (164) Restated equity attributable to owners of Rio Tinto as at 1 January 2018 44,542 IFRS 9 Financial Instruments The Group adopted IFRS 9 “Financial Instruments” on 1 January 2018, which resulted in changes in accounting policies and adjustments to the amounts recognised in the financial statements as at this date. The standard replaced the provisions of IAS 39 that relate to the recognition, classification and measurement of financial assets and financial liabilities; de-recognition of financial instruments; impairment of financial assets; and hedge accounting. The new accounting policies relating to financial instruments are set out in note 1. The prior period accounting policy is set out below. Prior period accounting policy: Financial instruments (i) Financial assets Classification The Group classifies its financial assets in the following categories: at fair value through profit or loss; loans and receivables; held-to-maturity; and available-for-sale investments. The classification depends on the purpose for which the financial assets were acquired. The Group’s policy with regard to financial risk management is set out in note 30. Generally, the Group does not acquire financial assets for the purpose of selling in the short term. When the Group enters into derivative contracts, these transactions are designed to reduce exposures related to assets and liabilities, firm commitments or anticipated transactions. Management determines the classification of financial assets at initial recognition. (a) Financial assets at fair value through profit or loss Assets in this category are classified as current assets if expected to be settled within 12 months, otherwise they are classified as non-current. Derivative assets, including embedded derivatives separated from the host contracts, are included within financial assets at fair value through profit or loss unless they are designated as hedging instruments. (b) Loans and receivables Loans and receivables comprise non-derivative financial assets with fixed or determinable payments that are not quoted in an active market. Trade receivables are included within this category; however, the embedded derivatives for provisional pricing included within some trade receivables are valued as explained in the prior period accounting policy for sales revenue, below. (c) Held-to-maturity Held-to-maturity investments are non-derivative financial assets with fixed or determinable payments and fixed maturity that the Group has the intention and ability to hold to maturity and which do not qualify as loans and receivables. Assets in this category are classified as Other investments and are classified as current assets or non-current assets based on their maturity. (d) Available-for-sale Available-for-sale financial assets are non-derivative financial assets that are either designated as available-for-sale or not classified in any of the other categories. Assets in this category are included in non-current assets unless the Group intends to dispose of the assets within 12 months of the balance sheet date or the asset matures within 12 months. Recognition and measurement Available-for-sale financial assets and financial assets at fair value through profit or loss are initially recognised at fair value and are subsequently measured at fair value. Initial transaction costs are expensed in the income statement for those assets at fair value through profit or loss. Loans and receivables and held-to-maturity financial assets are initially recognised at fair value plus transaction costs and are subsequently measured at amortised cost using the effective interest method. The fair values of the various derivative instruments used for hedging purposes are disclosed in note 30. Movements on the hedging reserve are disclosed in note 29. (ii) Financial liabilities Borrowings and other financial liabilities (including trade payables but excluding derivative liabilities) are recognised initially at fair value, net of transaction costs incurred, and are subsequently measured at amortised cost. The Group participates in supply chain finance arrangements whereby vendors may elect to receive early payment of their invoice from a bank by factoring their receivable from Rio Tinto. These arrangements do not modify the terms of the original liability and therefore, financial liabilities subject to supply chain finance continue to be classified as trade payables. Impact of transition to IFRS 9 “Financial Instruments” as at 1 January 2018 For transition, the Group has elected to apply the limited exemption in IFRS 9 relating to the classification, measurement and impairment requirements for financial assets and accordingly has not restated comparative periods. Any resulting adjustments to carrying values in the opening balance sheet have been recognised in opening retained earnings at 1 January 2018. The Group has elected for retrospective application for certain aspects of hedge accounting in particular relating to the treatment of the cost of hedging. The Group applies the new forward looking expected credit loss model required by IFRS 9, using the simplified approach for its trade receivables portfolio review and the general approach for all other financial assets as required by the standard. The impact of transition to IFRS 9 on the Group’s opening retained earnings as at 1 January 2018 is as follows: US$m Closing retained earnings 31 December 2017 23,761 Costs of hedging adjustment (22) Reclassification of equity investments from available-for-sale to FVPL 12 Impairment provision resulting from the application of the ECL model (7) Tax impact 1 Revaluation of funds 1 Adjustment to retained earnings from adoption of IFRS 9 on 1 January 2018 (sub-total) (15) Opening retained earnings 1 January 2018 – IFRS 9 (before restatement for IFRS 15) 23,746 A Classification and measurement of financial assets On 1 January 2018, the Group’s management assessed the classification of its financial assets on the basis of the contractual terms of their cash flows and the business model by which they are managed. Financial assets have been classified into the appropriate IFRS 9 categories below. Refer to note 1 for the Group’s revised financial asset classification and measurement policies. IFRS 9 classification at 1 January 2018 Held at FVPL Held at FVOCI (designated) Held at amortised cost IAS 39 classification at 1 January 2018 Total Held for trading Available-for-sale Loans & receivable, Held-to-maturity US$m US$m US$m US$m Opening balance – IAS 39 15,288 1,482 136 13,670 Cash and cash equivalents (a) (b) Reclassification of money market funds from amortised cost to FVPL - 7,813 - (7,813) Trade and other receivables (b) (c) Reclassification of trade and other receivables from amortised cost to FVPL - 1,316 - (1,316) Investments in equity shares and funds (d) Reclassification of investments from available-for-sale to FVPL - 90 (90) - Other investment including loans Reclassification of a financial asset from held-to-maturity to FVPL - 6 - (6) Opening balance – IFRS 9 (excluding expected credit losses and revaluation of funds) 15,288 10,707 46 4,535 Impairment provision resulting from the application of the ECL model (7) Revaluation of funds 1 Opening balance – IFRS 9 (including expected credit losses and revaluation of funds) 15,282 The material reclassification adjustments related to: (a) Money market funds of US$7.8 billion did not meet the strict solely principal and interest on principal (SPPI) criteria resulting in a reclassification from amortised cost to FVPL. These instruments continue to meet the IAS 7 “Statement of Cash Flows” criteria for classification as cash and cash equivalents and will continue to be included within net debt, as disclosed in note 24. (b) Due to the short-term nature of these financial assets the fair value of the reclassified assets does not differ significantly from their amortised cost. (c) Trade receivables of US$1.3 billion with embedded derivatives (relating to provisional pricing terms at the time control of goods passed) did not meet the SPPI criteria; these balances are considered in their entirety for classification purposes under IFRS 9. (d) Investments not meeting the SPPI test have been reclassified to FVPL. B Retained earnings and reserves Effect on Available-for-sale (AfS) reserve Effect on FVOCI reserve Costs of hedging reserve Cash flow hedge reserve Effect on retained earnings US$m US$m US$m US$m US$m Closing balance – 31 December 2017 20 - - 32 23,761 Reclassification of equity investments from AfS (e) (20) 8 - - 12 Impact of costs of hedging adjustment (f) - - 26 (4) (22) Impairment provisions (g) - - - - (7) Tax impact - - - - 1 Re-measurement of funds - - - - 1 Total impact (20) 8 26 (4) (15) Opening balance – 1 January 2018 - 8 26 28 23,746 (e) The Group has elected to classify certain equity investments as fair value through OCI. (f) The costs of hedging adjustment is explained in C below. (g) The impairment provision is explained in D below. C Derivatives and hedging activities The Group’s risk management strategies and associated hedge documentation have been aligned with the requirements of IFRS 9 and existing hedging relationships under IAS 39 have been treated as continuing hedges. Amendments to the hedge accounting rules under the new standard have allowed the Group to apply hedge accounting to the aluminium forward and option contracts embedded in the electricity purchase contracts of certain aluminium smelters thus reducing volatility in the income statement. IFRS 9 allows for the deferral of certain costs of hedging including foreign currency basis spreads. The Group has designated cross currency interest rate swaps as hedging instruments and excluded the foreign currency basis spreads from the hedge relationship. Changes in the foreign currency basis spread are included in a cost of hedging reserve and will be subsequently recycled to profit or loss as the hedged item impacts on profit or loss. The retrospective application for the treatment of foreign currency spreads has resulted in a transfer of US$22 million from retained earnings to the cost of hedging reserve and a transfer of US$4 million from the cash flow hedge reserve to the cost of hedging reserve. D Impairment of financial assets The Group implemented the new forward looking expected credit loss model which is required for certain financial instruments. The simplified approach was used for the trade receivables portfolio and the general approach was applied to all other financial assets requiring review. The transition impact of US$7 million on opening retained earnings is disclosed on page 220. IFRS 15 Revenue from contracts with customers IFRS 15 replaces IAS 18 “Revenue”. The prior period IAS 18 accounting policy is set out below: Prior period accounting policy: Sales revenue Sales revenue comprises sales to third parties. All shipping and handling costs incurred by the Group are recognised as operating costs. If the Group is acting solely as an agent, amounts billed to customers for shipping and handling are offset against the relevant costs. Revenue from services is recognised as those services are rendered to, and accepted by, the customer. Sales revenue excludes any applicable sales taxes. Mining royalties payable are presented as an operating cost or, where they are in substance a profit-based tax, within taxation. Revenues from the sale of significant by-products, such as gold, are included in sales revenue. Other operating income, incidental to the main revenue-generating activities of the operations, is treated as a credit to operating costs. Third-party commodity swap arrangements principally for delivery and receipt of smelter grade alumina are offset within operating costs. Sales of copper concentrate are stated at their invoiced amount which is net of treatment and refining charges. Sales revenue is only recognised on individual sales when all of the following criteria are met: – the significant risks and rewards of ownership of the product have been transferred to the buyer; – neither continuing managerial involvement to the degree usually associated with ownership, nor effective control over the goods sold, has been retained; – the amount of revenue can be measured reliably; – it is probable that the economic benefits associated with the sale will flow to the Group; and – the costs incurred or to be incurred in respect of the sale can be measured reliably. In most instances, sales revenue is recognised when the product is delivered to the destination specified by the customer, which is typically the vessel on which it will be shipped, the destination port or the customer’s premises. The Group’s products are sold to customers under contracts which vary in tenure and pricing mechanisms, including some volumes sold in the spot market. Sales revenue may be subject to adjustment if the product specification does not conform to the terms specified in the sales contract. Pricing for iron ore is on a range of terms, the majority being either monthly or quarterly average pricing mechanisms, with a smaller proportion of iron ore volumes being sold on the spot market. Certain of the Group’s products are provisionally priced at the date revenue is recognised; however, with the exception of copper, prices are generally finalised within the calendar quarter of the month of shipment. The final selling price is based on the price for the quotational period stipulated in the contract. Substantially all iron ore and aluminium sales are reflected at final prices in the results for the period. Final prices for copper concentrate are normally determined between 30 to 180 days after delivery to the customer. The change in value of the embedded pricing derivative included in the receivable is based on relevant forward market prices and is included in sales revenue. Information on provisionally priced sales contracts is included in note 30. Impact of transition to IFRS 15 “Revenue from Contracts with Customers” The impact of transition to IFRS 15 “Revenue from Contracts with Customers” as at 1 January 2018 is as follows: The core principle of IFRS 15 is that an entity recognises revenue related to the transfer of promised goods or services when control of the goods or services passes to the customer. The amount of revenue recognised should reflect the consideration to which the entity expects to be entitled in exchange for those goods or services. The Group has adopted the modified transitional approach to implementation and the new standard has therefore been applied only to contracts that remain in force at 1 January 2018. A US$164 million (US$235 million pre-tax) transition adjustment has been recognised in retained earnings on transition at 1 January 2018 without adjustment of comparatives. The adjustment reduces trade and other receivables by US$235 million and deferred tax liabilities by US$71 million. The transition adjustment related to an “uplift” arrangement with a partner in a joint operation whereby sales revenue was recognised under IAS 18 when the Group sold product from other operations to its partner to allow it to meet its contractual obligations when insufficient product was available in the jointly owned operation. The Group recognised an asset for product which will be receivable from the partner out of the partner’s share of future production of the joint operation. Under IFRS 15, such transactions with partners in joint operations cannot be recognised as sales revenue. The US$235 million receivable has accumulated over prior years. The change in accounting has no impact on the commercial arrangement or current or future cash flows. Under IFRS 15, sales revenue is recognised in the income statement when product is received from the partner and sold to a customer of the Group. The impact for the year is a US$19 million decrease in sales revenue compared with the amount that would have been reflected under IAS 18. The impact of all other measurement differences identified between IAS 18 and IFRS 15 was immaterial at 1 January 2018 and 31 December 2018.

Rio Tinto financial information

Rio Tinto financial information by business unit	12 Months Ended
	Dec. 31, 2018
Disclosure Of Financial Information By Business Unit [Abstract]
Rio Tinto financial information by business unit	Gross revenue (a) EBITDA (b) Net earnings (c) for the year ended 31 December for the year ended 31 December for the year ended 31 December Rio Tinto interest 2018 2017 2016 2018 2017 2016 2018 2017 2016 % US$m US$m US$m US$m US$m US$m US$m US$m US$m Iron Ore Pilbara (d) 18,359 18,143 14,530 11,267 11,383 8,558 6,460 6,576 4,662 Evaluation projects/other 126 108 75 58 137 (32 ) 54 116 (51 ) Total Iron Ore 18,485 18,251 14,605 11,325 11,520 8,526 6,514 6,692 4,611 Aluminium (e) Bauxite 2,324 2,019 1,913 790 804 848 412 463 493 Alumina 3,340 2,661 2,118 1,137 454 27 634 180 (121 ) Intrasegment (861 ) (790 ) (786 ) (7 ) (25 ) - (5 ) (17 ) - Bauxite & Alumina 4,803 3,890 3,245 1,920 1,233 875 1,041 626 372 Primary Metal 6,468 5,808 4,913 1,418 1,762 1,258 595 778 402 Pacific Aluminium 2,541 2,305 1,971 148 453 264 - 176 62 Inter-segment and other (3,226 ) (2,321 ) (1,822 ) (88 ) (19 ) (50 ) (67 ) (12 ) (13 ) Integrated operations 10,586 9,682 8,307 3,398 3,429 2,347 1,569 1,568 823 Other product group items 1,479 1,214 1,075 (440 ) (132 ) (42 ) (344 ) (100 ) (30 ) Product group operations 12,065 10,896 9,382 2,958 3,297 2,305 1,225 1,468 793 Evaluation projects/other 126 109 76 137 126 167 122 115 154 Total Aluminium 12,191 11,005 9,458 3,095 3,423 2,472 1,347 1,583 947 Copper & Diamonds Rio Tinto Kennecott 100.0 1,862 1,352 1,243 785 539 126 293 78 (228 ) Escondida 30.0 2,274 1,811 1,465 1,301 1,030 793 506 325 270 Grasberg joint venture (g) 457 33 - 281 (3 ) (17 ) 217 (169 ) (64 ) Oyu Tolgoi and Turquoise Hill (h) 1,180 940 1,203 375 256 436 69 36 52 Diamonds (i) 695 706 613 301 287 239 118 92 47 Product group operations 6,468 4,842 4,524 3,043 2,109 1,577 1,203 362 77 Evaluation projects/other - - - (267 ) (205 ) (190 ) (149 ) (99 ) (95 ) Total Copper & Diamonds 6,468 4,842 4,524 2,776 1,904 1,387 1,054 263 (18 ) Energy & Minerals Rio Tinto Coal Australia (j) 989 2,829 2,634 893 1,223 893 591 716 382 Iron Ore Company of Canada 58.7 1,583 1,867 1,324 586 770 335 166 235 64 Rio Tinto Iron & Titanium (k) 1,782 1,763 1,419 510 546 370 174 201 86 Rio Tinto Borates 100.0 622 630 620 197 244 213 111 126 117 Dampier Salt 68.4 246 215 259 56 27 74 18 3 25 Uranium (l) 415 417 456 18 15 54 (4 ) (26 ) 10 Product group operations 5,637 7,721 6,712 2,260 2,825 1,939 1,056 1,255 684 Simandou iron ore project (m) - - - (15 ) (13 ) (102 ) (7 ) (6 ) (47 ) Evaluation projects/other 60 43 22 (52 ) (9 ) (31 ) (37 ) (7 ) (25 ) Total Energy & Minerals 5,697 7,764 6,734 2,193 2,803 1,806 1,012 1,242 612 Other operations (n) 9 10 8 (70 ) (116 ) (95 ) (102 ) (138 ) (88 ) Inter-segment transactions (15 ) (15 ) (11 ) - - - - - - Product group total 42,835 41,857 35,318 19,319 19,534 14,096 9,825 9,642 6,064 Central pension costs, share-based payments and insurance (128 ) (68 ) (34 ) (90 ) (48 ) (24 ) Restructuring, project and one-off costs (272 ) (177 ) (13 ) (190 ) (124 ) (9 ) Central costs (552 ) (491 ) (364 ) (410 ) (311 ) (208 ) Exploration and evaluation (231 ) (218 ) (175 ) (193 ) (178 ) (147 ) Net interest (134 ) (354 ) (576 ) Underlying EBITDA/earnings 18,136 18,580 13,510 8,808 8,627 5,100 Items excluded from underlying EBITDA/earnings - 10 18 5,127 1,912 (687 ) 4,830 135 (483 ) EBITDA/net earnings 23,263 20,492 12,823 13,638 8,762 4,617 Reconciliation to Group income statement Share of equity accounted unit sales and intra-subsidiary/equity accounted unit sales (2,313 ) (1,837 ) (1,555 ) Depreciation and amortisation in subsidiaries excluding capitalised depreciation (3,909 ) (4,302 ) (4,691 ) Impairment charges (132 ) (796 ) (249 ) Depreciation and amortisation in equity accounted units (650 ) (648 ) (526 ) Taxation and finance items in equity accounted units (372 ) (272 ) (241 ) Consolidated sales revenue/profit on ordinary activities before finance items and taxation 40,522 40,030 33,781 18,200 14,474 7,116 Depreciation and Capital expenditure (o) amortisation Operating assets (p) Employees for the year ended 31 December for the year ended 31 December as at for the year ended 31 December Rio Tinto interest 2018 2017 2016 2018 2017 2016 2018 2017 2016 2018 2017 2016 % US$m US$m US$m US$m US$m US$m US$m US$m US$m Number Number Number Iron Ore Pilbara (d) 1,288 1,201 868 1,682 1,645 1,645 14,486 16,535 16,357 10,422 10,159 10,424 Evaluation projects/other - - - - - - 2 2 2 - - - Total Iron Ore 1,288 1,201 868 1,682 1,645 1,645 14,488 16,537 16,359 10,422 10,159 10,424 Aluminium (e) Bauxite 953 825 343 165 123 110 2,494 1,897 1,278 2,676 2,534 2,592 Alumina 218 108 87 194 209 206 2,721 2,733 2,588 2,009 2,012 2,139 Intrasegment - - - - (20 ) (18 ) - - - - Bauxite & Alumina 1,171 933 430 359 332 316 5,195 4,612 3,866 4,685 4,546 4,731 Primary Metal 595 389 394 615 665 716 9,306 9,946 10,701 6,497 6,404 6,799 Pacific Aluminium 115 109 91 149 196 193 1,156 1,016 1,044 2,278 2,173 2,276 Inter-segment and other - 5 1 (1 ) 6 25 789 772 171 180 222 231 Integrated operations 1,881 1,436 916 1,122 1,199 1,250 16,446 16,346 15,782 13,640 13,345 14,037 Other product group items (f) (508 ) - - - - - - - - - - - Total Aluminium 1,373 1,436 916 1,122 1,199 1,250 16,446 16,346 15,782 13,640 13,345 14,037 Copper & Diamonds Rio Tinto Kennecott 100.0 318 249 333 427 422 530 1,864 1,936 2,189 1,993 1,734 1,638 Escondida 30.0 302 248 517 518 507 364 3,057 3,369 3,565 1,087 1,079 1,230 Grasberg joint venture (g) 171 138 174 30 42 89 - 1,137 1,151 1,615 1,642 2,859 Oyu Tolgoi and Turquoise Hill (h) 1,284 901 322 219 344 450 6,072 4,725 3,804 2,863 2,835 2,728 Diamonds (i) 64 85 97 118 132 164 267 441 655 967 922 907 Product group operations 2,139 1,621 1,443 1,312 1,447 1,597 11,260 11,608 11,364 8,525 8,212 9,362 Evaluation projects/other 11 1 (2 ) 5 5 4 129 135 166 146 142 127 Total Copper & Diamonds 2,150 1,622 1,441 1,317 1,452 1,601 11,389 11,743 11,530 8,671 8,354 9,489 Energy & Minerals Rio Tinto Coal Australia (j)/(q) 32 84 (107 ) 34 152 297 (837 ) 1,040 1,807 1,005 1,924 3,049 Iron Ore Company of Canada 58.7 189 202 75 154 157 151 975 988 1,018 2,397 2,382 2,308 Rio Tinto Iron & Titanium (k) 169 119 97 201 219 189 3,390 3,881 3,662 4,058 4,048 4,094 Rio Tinto Borates 100.0 44 28 31 62 65 53 518 523 508 980 936 984 Dampier Salt 68.4 14 13 11 20 22 23 165 150 146 239 232 317 Uranium (l) 8 21 30 4 37 25 (406 ) (327 ) (143 ) 1,324 1,307 1,303 Product group operations 456 467 137 475 652 738 3,805 6,255 6,998 10,003 10,829 12,055 Simandou iron ore project (m) - - - - - - 15 17 13 70 10 635 Evaluation projects/other - - 4 - - 1 41 41 38 33 25 763 Total Energy & Minerals 456 467 141 475 652 739 3,861 6,313 7,049 10,106 10,864 13,453 Other operations (n) 12 (35 ) (11 ) 26 32 34 (442 ) (328 ) 203 187 203 249 Product group total 5,279 4,691 3,355 4,622 4,980 5,269 45,742 50,611 50,923 43,026 42,925 47,652 Inter-segment transactions 129 206 142 Net assets/(liabilities) of disposal groups held for sale (r) 440 370 (7 ) Other items 65 70 (46 ) 43 42 51 (2,880 ) (2,631 ) (2,181 ) 4,432 3,882 3,377 Less: equity accounted units (500 ) (417 ) (651 ) (650 ) (647 ) (526 ) - - - - - - Total 4,844 4,344 2,658 4,015 4,375 4,794 43,431 48,556 48,877 47,458 46,807 51,029 Add back: Proceeds from disposal of property, plant and equipment 586 138 354 Total capital expenditure per cash flow statement 5,430 4,482 3,012 Less: Net cash/(debt) 255 (3,845 ) (9,587 ) Less: EAU funded balances excluded from net debt - - - Equity attributable to owners of Rio Tinto 43,686 44,711 39,290 Business units are classified according to the Group’s management structure. a) Gross sales revenue includes the sales revenue of equity accounted units on a proportionately consolidated basis (after adjusting for sales to subsidiaries) in addition to consolidated sales. Consolidated sales revenue includes subsidiary sales to equity accounted units which are not included in gross sales revenue. b) EBITDA of subsidiaries and the Group's share of EBITDA relating to equity accounted units represents profit before: tax, net finance items, depreciation and amortisation charged to the income statement in the period. Underlying EBITDA excludes the EBITDA impact of the same items that are excluded from underlying earnings. c) Represents profit after tax for the period attributable to the owners of the Rio Tinto Group. Business unit earnings are stated before finance items but after the amortisation of discount related to provisions. Earnings attributed to business units do not include amounts that are excluded in arriving at underlying earnings. d) Pilbara represents the Group’s 100% holding in Hamersley, 50% holding of Hope Downs Joint Venture and 65% holding of Robe River Iron Associates. The Group’s net beneficial interest in Robe River Iron Associates is 53%, as 30% is held through a 60% owned subsidiary and 35% is held through a 100% owned subsidiary. e) Presented on an integrated operations basis, splitting activities between Bauxite & Alumina, Primary Metal, Pacific Aluminium and Other integrated operations (which reflect the results of the integrated production of aluminium) and other product group items which relate to other commercial activities. f) Aluminium capital expenditure is reported net of US$508 million proceeds received on the sale of surplus land at Kitimat. These proceeds are not included in Aluminium’s free cash flow and the associated gain is excluded from business unit earnings and EBITDA. g) Through a joint venture agreement with Freeport-McMoRan Inc. (Freeport), we were entitled to 40% of material mined above an agreed threshold as a consequence of expansions and developments of the Grasberg facilities since 1998 (until 21 December 2018). On 28 September 2018, we entered into a binding agreement to sell our entire interest in the Grasberg mine to PT Indonesia Asahan Aluminium (Persero) (Inalum). The sale completed on 21 December 2018. h) Our interest in Oyu Tolgoi is held indirectly through our 50.8% investment in Turquoise Hill Resources Ltd (TRQ), where TRQ’s principal asset is its 66% investment in Oyu Tolgoi LLC, which owns the Oyu Tolgoi copper-gold mine. i) Includes our interests in Argyle (100%) and Diavik (60%). j) Includes our 82% interest in the Hail Creek coal mine (until 1 August 2018), our 80% interest in the Kestrel underground coal mine (until 1 August 2018) and interests in the Winchester South (until 1 June 2018) and Valeria development projects (until 1 August 2018). On 1 June 2018, we sold our entire 75% interest in the Winchester South coal development project in Queensland, Australia, to Whitehaven Coal Limited for US$200 million. On 1 August 2018, we sold our entire 82% interest in the Hail Creek coal mine and 71.2% interest in the Valeria coal development project in Queensland, Australia, to Glencore for US$1.7 billion. On 1 August 2018, we sold our entire 80% interest in the Kestrel underground coal mine in Queensland, Australia, to a consortium comprising private equity manager EMR Capital (EMR) and PT Adaro Energy Tbk (Adaro), an Indonesian listed coal company, for US$2.25 billion. On 1 September 2017, we sold our 100% shareholding in Coal & Allied Industries Limited to Yancoal Australia Limited for US$2.69 billion (before working capital adjustments). Rio Tinto Coal Australia’s operating assets of US$(837) million at 31 December 2018 include provisions for onerous contracts in relation to rail infrastructure capacity and capital gains tax payable on the divestments announced in the year, partly offset by financial assets and receivables relating to contingent royalties and disposal proceeds. k) Includes our interests in Rio Tinto Fer et Titane (100%), QIT Madagascar Minerals (QMM, 80%) and Richards Bay Minerals (attributable interest of 74%). l) Includes our interests in Energy Resources of Australia (68.4%) and Rössing Uranium Limited (Rössing) (68.6%). On 26 November 2018, we entered into a binding agreement with China National Uranium Corporation Limited (CNUC) to sell our entire 68.6% interest in the Rössing mine in Namibia, subject to certain conditions. m) Simfer Jersey Limited, a company incorporated in Jersey in which the Group has a 53% interest, has an 85% interest in Simfer S.A., the company that manages the Simandou project in Guinea. The Group therefore has a 45.05% indirect interest in Simfer S.A. These entities are consolidated as subsidiaries and together referred to as the Simandou iron ore project. n) Other operations include our 100% interest in the curtailed Gove alumina refinery and Rio Tinto Marine. o ) Capital expenditure is the net cash outflow on purchases less sales of property, plant and equipment, capitalised evaluation costs and purchases less sales of other intangible assets. The details provided include 100% of subsidiaries’ capital expenditure and Rio Tinto’s share of the capital expenditure of joint operations and equity accounted units. p) Operating assets of subsidiaries is comprised of net assets excluding post-retirement assets and liabilities, net of tax, and before deducting net debt. Operating assets are stated after the deduction of non-controlling interests – these are calculated by reference to the net assets of the relevant companies (ie inclusive of such companies’ debt and amounts due to or from Rio Tinto Group companies). q) Capital expenditure in 2016 for Rio Tinto Coal Australia includes net proceeds of US$192 million for the sale of our 100% interest in the Mount Pleasant thermal coal project to MACH Energy Australia Pty Ltd on 5 August 2016. r) Assets and liabilities held for sale at 31 December 2018 include our interest in Rössing Uranium Limited, the ISAL smelter, the Aluchemie anode plant, and the Alufluor aluminium fluoride plant. Assets and liabilities held for sale at 31 December 2017 included our interest in the Dunkerque aluminium smelter and certain other separate assets. Assets and liabilities held for sale at 31 December 2016 included our interests in the Blair Athol coal project and certain separate assets.

Principal accounting policies (

Principal accounting policies (Policies)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Accounting Policies [Abstract]
Accounting convention	(a) Accounting convention The financial information included in the financial statements for the year ended 31 December 2018, and for the related comparative periods, has been prepared under the historical cost convention, as modified by the revaluation of certain derivative contracts and financial assets, the impact of fair value hedge accounting on the hedged item and the accounting for post-employment assets and obligations. The Group’s policy in respect of these items is set out in the notes below. All financial statement values are rounded to the nearest million (US$m) unless otherwise stated. Where applicable, comparatives have been adjusted to measure or present them on the same basis as current period figures.
Basis of consolidation	(b) Basis of consolidation (notes 33 to 36) All intragroup transactions and balances have been eliminated on consolidation. Where necessary, adjustments are made to the locally reported assets, liabilities, and results of subsidiaries, joint arrangements and associates to bring their accounting policies in line with those used by the Group. Subsidiaries: Subsidiaries are entities controlled by either of the Companies. Control exists where either of the Companies has: power over the entities, that is, existing rights that give it the current ability to direct the relevant activities of the entities (those that significantly affect the Companies’ returns); exposure, or rights, to variable returns from its involvement with the entities; and the ability to use its power to affect those returns. Subsidiaries are fully consolidated from the date on which the Group obtains control. They are deconsolidated from the date that control ceases. Joint arrangements: A joint arrangement is an arrangement in which two or more parties have joint control. Joint control is the contractually agreed sharing of control such that decisions about the relevant activities of the arrangement (those that significantly affect the Companies’ returns) require the unanimous consent of the parties sharing control. The Group has two types of joint arrangements: Joint operations (JO): A JO is a joint arrangement in which the parties that share joint control have rights to the assets, and obligations for the liabilities, relating to the arrangement. This includes situations where the parties benefit from the joint activity through a share of the output, rather than by receiving a share of the results of trading. In relation to its interest in a JO, the Group recognises: its share of assets and liabilities; revenue from the sale of its share of the output and its share of any revenue generated from the sale of the output by the JO; and its share of expenses. All such amounts are measured in accordance with the terms of the arrangement, which is usually in proportion to the Group’s interest in the JO. These amounts are recorded in the Group’s financial statements on the appropriate lines. Joint ventures (JV): A JV is a joint arrangement in which the parties that share joint control have rights to the net assets of the arrangement. JVs are accounted for using the equity accounting method. Other unincorporated arrangements: In some cases, the Group participates in unincorporated arrangements and has rights to its share of the assets and obligations for its share of the liabilities of the arrangement rather than a right to a net return, but does not share joint control. In such cases, the Group recognises: its share of assets and liabilities; revenue from the sale of its share of the output and its share of any revenue generated from the sale of the output by the unincorporated arrangement; and its share of expenses. All such amounts are measured in accordance with the terms of the arrangement, which is usually in proportion to the Group’s interest in the arrangement. These amounts are recorded in the Group’s financial statements on the appropriate lines. Associates: An associate is an entity that is neither a subsidiary nor a joint arrangement, over which the Group has significant influence. Significant influence is presumed to exist where there is neither control nor joint control and the Group has more than 20% of the voting rights, unless it can be clearly demonstrated that this is not the case. Significant influence can arise where the Group holds less than 20% of the voting rights if it has the power to participate in the financial and operating policy decisions affecting the entity. Investments in associates are accounted for using the equity accounting method . The Group uses the term “equity accounted units” (EAUs) to refer to associates and JVs collectively. Under the equity accounting method the investment is recorded initially at cost to the Group, including any goodwill on acquisition. In subsequent periods the carrying amount of the investment is adjusted to reflect the Group’s share of the EAUs’ retained post-acquisition profit or loss and other comprehensive income. Long-term loans to EAUs that in substance form part of the Group’s net investment (quasi equity loans) are financial assets but are included in the line “Investments in equity accounted units” on the face of the balance sheet. When the Group’s share of losses in an EAU equals or exceeds its interest in the EAU, including such long-term loans and any other unsecured receivables, the Group does not recognise further losses, unless it has incurred legal or constructive obligations to continue to make payments on behalf of the EAU. Acquisitions (note 37) Under the “acquisition” method of accounting for business combinations, the purchase consideration is allocated to the identifiable assets acquired and liabilities and contingent liabilities assumed (the identifiable net assets) on the basis of their fair value at the date of acquisition, which is the date on which control is obtained. The consideration transferred for the acquisition of a subsidiary comprises the fair values of the assets transferred, the liabilities incurred to the former owners of the acquiree, the fair value of any asset or liability resulting from a contingent consideration arrangement and any equity interests issued by the Group. Costs related to the acquisition of a subsidiary are expensed as incurred. The excess of the consideration transferred, the amount of any non-controlling interest in the acquiree and the acquisition date fair value of any previous equity interest in the acquiree over the fair value of the identifiable net assets acquired is recorded as goodwill. Any shortfall is immediately recognised in the income statement. Non-controlling interests in the acquiree, that are present ownership interests and entitle their holders to a proportionate share of the entity’s net assets in the event of liquidation, are recognised by the Group in one of two ways with the choice being available on an acquisition-by-acquisition basis. They can be measured at either the non-controlling interest’s proportionate share of the acquiree’s identifiable net assets or at fair value. In some cases, non-controlling interests may be treated as equity options and valued on that basis. Goodwill (see note (e)) and amounts attributable to non-controlling interests will differ depending on the basis used. Where the Group previously held a non-controlling interest in the acquiree, this is remeasured to fair value at the date control is obtained with any gain or loss recognised in the income statement. The cash cost of the share purchase that gives rise to control is included within “Investing activities” in the cash flow statement. Where the Group increases its ownership interest in a subsidiary, the difference between the purchase price and the carrying value of the share of net assets acquired is recorded in equity. The cash cost of such purchases is included within “Financing activities” in the cash flow statement. Provisional fair values allocated at a reporting date are finalised within 12 months of the acquisition date. The results of businesses acquired during the year are included in the consolidated financial statements from the date on which control, joint control or significant influence is obtained. Disposals (note 37) Individual non-current assets or “disposal groups” (that is, groups of assets and liabilities) to be disposed of by sale or otherwise in a single transaction are classified as “held for sale” if the following criteria are met at the period end: – T he carrying amount will be recovered principally through a sale transaction rather than through continuing use; and – The disposal group is available for immediate sale in its present condition subject only to terms that are usual and customary for such sales; and – The sale is highly probable. Disposal groups held for sale are carried at the lower of their carrying amount and fair value less costs to sell. The comparative balance sheet is not restated. Disposal groups acquired with a view to resale are held at the fair value determined at the acquisition date. For these assets acquired for resale no profits or losses are recognised between the acquisition date and the disposal date, unless there is a subsequent impairment. On classification as held for sale, the assets are no longer depreciated and, if applicable, equity accounting ceases. If control is lost, any interest in the entity retained by the Group is remeasured to its fair value and the change in carrying amount is recognised in the income statement. The retained interest may be subsequently accounted for as a joint venture, joint operation, associate or financial asset depending on the facts. Certain amounts previously recognised in other comprehensive income in respect of the entity disposed of, or for which control, joint control or significant influence has ceased, may be recycled to the income statement. The cash proceeds of disposals are included within “Investing activities” in the cash flow statement. Changes in the Group’s interest in a subsidiary that do not result in a loss of control are accounted for in equity. The cash proceeds of such disposals are included within “Financing activities” in the cash flow statement. (c) Sales revenue Recognition and measurement The Group recognises sales revenue related to the transfer of promised goods or services when control of the goods or services passes to the customer. The amount of revenue recognised reflects the consideration to which the Group is or expects to be entitled in exchange for those goods or services.
Sales revenue	(c) Sales revenue Recognition and measurement The Group recognises sales revenue related to the transfer of promised goods or services when control of the goods or services passes to the customer. The amount of revenue recognised reflects the consideration to which the Group is or expects to be entitled in exchange for those goods or services. Notes to the 2018 financial statements continued 1 Principal accounting policies continued Sales revenue is recognised on individual sales when control transfers to the customer. In most instances, control passes and sales revenue is recognised when the product is delivered to the vessel or vehicle on which it will be transported once loaded, the destination port or the customer’s premises. There may be circumstances when judgment is required based on the five indicators of control below. – The customer has the significant risks and rewards of ownership and has the ability to direct the use of, and obtain substantially all of the remaining benefits from, the goods or service. – The customer has a present obligation to pay in accordance with the terms of the sales contract. For shipments under the Incoterms Cost, Insurance and Freight (CIF)/Carriage Paid to (CPT)/Cost and Freight (CFR) this is generally when the ship is loaded, at which time the obligation for payment is for both product and freight. – The customer has accepted the asset. Sales revenue may be subject to adjustment if the product specification does not conform to the terms specified in the sales contract but this does not impact the passing of control. Assay and specification adjustments have been immaterial historically. – The customer has legal title to the asset. The Group usually retains legal title until payment is received for credit risk purposes only. – The customer has physical possession of the asset. This indicator may be less important as the customer may obtain control of an asset prior to obtaining physical possession, which may be the case for goods in transit. The Group sells a significant proportion of its products on CFR or CIF Incoterms. This means that the Group is responsible (acts as principal) for providing shipping services and, in some instances, insurance after the date at which control of goods passes to the customer at the loading port. The Group therefore has separate performance obligations for freight and insurance services that are provided solely to facilitate sale of the commodities it produces. Other Incoterms commonly used by the Group are Free on Board (FOB), where the Group has no responsibility for freight or insurance once control of the goods has passed at the loading port, and Delivered at Place (DAP) where control of the goods passes when the product is delivered to the agreed destination. For these Incoterms there is only one performance obligation, being for provision of product at the point where control passes. The Group’s products are sold to customers under contracts which vary in tenure and pricing mechanisms, including some volumes sold in the spot market. Pricing for iron ore is on a range of terms, the majority being either monthly or quarterly average pricing mechanisms, with a smaller proportion of iron ore volumes being sold on the spot market. Within each sales contract, each unit of product shipped is a separate performance obligation. Revenue is generally recognised at the contracted price as this reflects the stand-alone selling price. Sales revenue excludes any applicable sales taxes. Mining royalties payable are presented as an operating cost or, where they are in substance a profit-based tax, within taxation. Sales of copper concentrate are stated net of the treatment and refining charges which will be required to convert it to an end product. Certain of the Group’s products may be provisionally priced at the date revenue is recognised; however, substantially all iron ore and aluminium sales are reflected at final prices in the results for the period. The final selling price for all provisionally priced products is based on the price for the quotational period stipulated in the contract. Final prices for copper concentrate are normally determined between 30 to 180 days after delivery to the customer. The change in value of the provisionally priced receivable is based on relevant forward market prices and is included in sales revenue. Rio Tinto has a number of long-term contracts to supply product to customers in future periods. Generally, revenues are recognised on an as invoiced basis, hence, the right to consideration from a customer corresponds directly with the entity’s performance completed to date. A number of the Group’s businesses provide volume discounts in certain circumstances. The impact of constraining such variable consideration under IFRS 15 was immaterial at 31 December 2018. The Group applies the practical expedient in paragraph 121 of IFRS 15 and does not disclose information on the transaction price allocated to performance obligations that are unsatisfied. Presentation and disclosures Consolidated sales revenue as reported in the income statement comprises sales to third parties. Certain of the Group’s products may be provisionally priced at the date revenue is recognised. Sales revenue includes revenue from contracts with customers, which is accounted for under IFRS 15 “Revenue from Contracts with Customers” and subsequent movements in provisionally priced receivables which are accounted for under IFRS 9 “Financial Instruments”. A breakdown of sales revenue between these two amounts is disclosed in the product analysis in note 3 and further detail on provisional pricing in note 3. Sales revenue includes revenue from movements in provisionally priced receivables, consistent with the treatment in prior periods. The Group considers that the impact of economic factors on its sales revenue, particularly pricing and volumes, is best understood by reference to the disclosure of sales revenue by product group and sales destination in note 3. The analysis of provisional pricing adjustments by commodity in the product analysis in note 3 shows which products are subject to price volatility post the transfer of control. With the exception of Oyu Tolgoi, which sells copper concentrate to China, this price uncertainty is largely resolved at the period end. Typically, the Group has a right to payment before or at the point that control of the goods passes including a right, where applicable, to payment for provisionally priced products and unperformed freight and insurance services. Cash received before control passes is recognised as a contract liability. The amount of consideration does not contain a significant financing component as payment terms are less than one year. Revenues from the sale of significant by-products, such as gold, are included in sales revenue. Sundry revenue (eg sales of surplus power) incidental to the main revenue-generating activities of the operations, is treated as a credit to operating costs. The Group does not disclose sales revenue from freight and insurance services separately as it does not consider that this is necessary in order to understand the impact of economic factors on the Group; the Group’s chief executive, the chief operating decision maker, as defined under IFRS 8, “Operating Segments”, does not review information specifically relating to these sources of revenue in order to evaluate the performance of business segments and Group information on these sources of revenue is not provided externally. The Group does provide information on freight revenue for the iron ore and bauxite businesses on pages 36 and 41 to help stakeholders understand FOB operating margins for those products. Third-party commodity swap arrangements principally for delivery and receipt of smelter-grade alumina are offset within operating costs. Presentation of comparative consolidated sales revenue is in accordance with the previous standard IAS 18 “Revenue Recognition”. No material measurement or recognition differences on comparative information were identified between IAS 18 and the current standard IFRS 15. For further understanding of the impact of the transition to IFRS 15, refer to note 45.
Currency translation	(d) Currency translation The functional currency for each entity in the Group, and for joint arrangements and associates, is the currency of the primary economic environment in which that entity operates. For many of these entities, this is the currency of the country in which they are located. Transactions denominated in other currencies are converted to the functional currency at the exchange rate ruling at the date of the transaction. Monetary assets and liabilities denominated in foreign currencies are retranslated at period-end exchange rates. The Group’s financial statements are presented in US dollars, as that presentation currency most reliably reflects the global business performance of the Group as a whole. On consolidation, income statement items for each entity are translated from the functional currency into US dollars at average rates of exchange, except for material one-off transactions, which are translated at the rate prevailing on the transaction date. Balance sheet items are translated into US dollars at period-end exchange rates. Exchange differences arising on the translation of the net assets of entities with functional currencies other than the US dollar are recognised directly in the currency translation reserve. These translation differences are shown in the statement of comprehensive income, with the exception of translation adjustments relating to Rio Tinto Limited’s share capital, which are shown in the statement of changes in equity. Where an intragroup balance is, in substance, part of the Group’s net investment in an entity, exchange gains and losses on that balance are taken to the currency translation reserve. Except as noted above, or in note 1(p) relating to derivative contracts, all other exchange differences are charged or credited to the income statement in the year in which they arise.
Goodwill and intangible assets (excluding exploration and evaluation expenditure)	(e) Goodwill and intangible assets (excluding exploration and evaluation expenditure) (notes 12 and 13) Goodwill is not amortised; it is tested annually for impairment or more frequently if events or changes in circumstances indicate a potential impairment. Investments in EAUs, including any goodwill, are tested for impairment as a single asset when a trigger for impairment has been identified. The Group’s impairment policy is explained in note 1(i). Purchased intangible assets are initially recorded at cost. Finite-life intangible assets are amortised over their useful economic lives on a straight line or units of production basis, as appropriate. Intangible assets that are deemed to have indefinite lives and intangible assets that are not yet ready for use are not amortised; they are reviewed annually for impairment or more frequently if events or changes in circumstances indicate a potential impairment in accordance with accounting policy note 1(i). The Group considers that intangible assets have indefinite lives when, based on an analysis of all of the relevant factors, there is no foreseeable limit to the period over which the asset is expected to generate cash flows for the Group. The factors considered in making this judgment include the existence of contractual rights for unlimited terms or evidence that renewal of the contractual rights without significant incremental cost can be expected for indefinite future periods in view of the Group’s investment intentions. The life cycles of the products and processes that depend on the asset are also considered.
Exploration and evaluation	(f) Exploration and evaluation (note 13) Exploration and evaluation expenditure comprises costs that are directly attributable to: – Researching and analysing existing exploration data; – Conducting geological studies, exploratory drilling and sampling; – Examining and testing extraction and treatment methods; and/or – Compiling various studies (order of magnitude, prefeasibility and feasibility). Exploration expenditure relates to the initial search for deposits with economic potential. Expenditure on exploration activity undertaken by the Group is not capitalised. Evaluation expenditure relates to a detailed assessment of deposits or other projects (including smelter and refinery projects) that have been identified as having economic potential. Capitalisation of evaluation expenditure commences when there is a high degree of confidence that the Group will determine that a project is commercially viable, that is the project will provide a satisfactory return relative to its perceived risks, and therefore it is considered probable that future economic benefits will flow to the Group. The Group’s view is that a high degree of confidence is greater than “more likely than not” (that is, greater than 50% certainty) and less than “virtually certain” (that is, less than 90% certainty). Assessing whether there is a high degree of confidence that the Group will ultimately determine that an evaluation project is commercially viable requires judgment and consideration of all relevant factors such as the nature and objective of the project; the project’s current stage; project timeline; current estimates of the project’s net present value, including sensitivity analyses for the key assumptions; and the main risks of the project. Development expenditure incurred prior to the decision to proceed is subject to the same criteria for capitalisation, being a high degree of confidence that the Group will ultimately determine that a project is commercially viable. In some cases, undeveloped projects are regarded as successors to orebodies, smelters or refineries currently in production. Where this is the case, it is intended that these will be developed and go into production when the current source of ore is exhausted or when existing smelters or refineries are closed. Ore reserves may be declared for an undeveloped mining project before its commercial viability has been fully determined. Evaluation costs may continue to be capitalised during the period between declaration of ore reserves and approval to mine as further work is undertaken in order to refine the development case to maximise the project’s returns. In accordance with IFRS 6 “Exploration for and Evaluation of Mineral Resources”, the criteria for the capitalisation of evaluation costs are applied consistently from period to period. In the case of undeveloped mining projects that have arisen through acquisition, the allocation of the purchase price consideration may result in undeveloped properties being recognised at an earlier stage of project evaluation compared with projects arising from the Group’s exploration and evaluation programme. Subsequent expenditure on acquired undeveloped projects is only capitalised if it meets the high degree of confidence threshold discussed above. The carrying values of capitalised evaluation expenditure for undeveloped mining projects (projects for which the decision to mine has not yet been approved at the appropriate authorisation level within the Group) are reviewed at each reporting date for indicators of impairment in accordance with IFRS 6, and when indicators that are identified are tested in accordance with IAS 36. Evaluation expenditure for non-mining projects is reviewed and tested under IAS 36. The impairment review is based on a status report summarising the Group’s intentions to recover value through development, sale or other partnering arrangements. If a project does not prove viable
Property, plant and equipment	(g) Property, plant and equipment (note 14) Once an undeveloped mining project has been determined as commercially viable and approval to mine has been given, expenditure other than that on land, buildings, plant, equipment and capital work in progress is capitalised under “Mining properties and leases” together with any amount transferred from “Exploration and evaluation”. Costs which are necessarily incurred whilst commissioning new assets, in the period before they are capable of operating in the manner intended by management, are capitalised. Development costs incurred after the commencement of production are capitalised to the extent they are expected to give rise to a future economic benefit. Interest on borrowings related to construction or development projects is capitalised, at the rate payable on project-specific debt if applicable or at the Group or subsidiary’s cost of borrowing if not, until the point when substantially all the activities that are necessary to make the asset ready for its intended use are complete. It may be appropriate to use a subsidiary’s cost of borrowing when the debt was negotiated based on the financing requirements of that subsidiary. Property, plant and equipment is stated at cost, as defined in IAS 16, less accumulated depreciation and accumulated impairment losses. The cost of property, plant and equipment includes, where applicable, the estimated close-down and restoration costs associated with the asset.
Deferred stripping	Notes to the 2018 financial statements continued 1 Principal accounting policies continued (h) Deferred stripping (note 14) In open pit mining operations, overburden and other waste materials must be removed to access ore from which minerals can be extracted economically. The process of removing overburden and waste materials is referred to as stripping. During the development of a mine (or, in some instances, pit; see below), before production commences, stripping costs related to a component of an orebody are capitalised as part of the cost of construction of the mine (or pit) and are subsequently amortised over the life of the mine (or pit) on a units of production basis. Where a mine operates several open pits that are regarded as separate operations for the purpose of mine planning, initial stripping costs are accounted for separately by reference to the ore from each separate pit. If, however, the pits are highly integrated for the purpose of mine planning, the second and subsequent pits are regarded as extensions of the first pit in accounting for stripping costs. In such cases, the initial stripping (ie overburden and other waste removal) of the second and subsequent pits is considered to be production phase stripping (see below). The Group’s judgment as to whether multiple pit mines are considered separate or integrated operations depends on each mine’s specific circumstances. The following factors would point towards the initial stripping costs for the individual pits being accounted for separately: – If mining of the second and subsequent pits is conducted consecutively following that of the first pit, rather than concurrently – If separate investment decisions are made to develop each pit, rather than a single investment decision being made at the outset – If the pits are operated as separate units in terms of mine planning and the sequencing of overburden removal and ore mining, rather than as an integrated unit – If expenditures for additional infrastructure to support the second and subsequent pits are relatively large – If the pits extract ore from separate and distinct orebodies, rather than from a single orebody If the designs of the second and subsequent pits are significantly influenced by opportunities to optimise output from several pits combined, including the co-treatment or blending of the output from the pits, then this would point to treatment as an integrated operation for the purposes of accounting for initial stripping costs. The relative importance of each of the above factors is considered in each case. In order for production phase stripping costs to qualify for capitalisation as a stripping activity asset, three criteria must be met: – It must be probable that there will be an economic benefit in a future accounting period because the stripping activity has improved access to the orebody; – It must be possible to identify the “component” of the orebody for which access has been improved; and – It must be possible to reliably measure the costs that relate to the stripping activity. A “component” is a specific section of the orebody that is made more accessible by the stripping activity. It will typically be a subset of the larger orebody that is distinguished by a separate useful economic life (for example, a pushback). Production phase stripping can give rise to two benefits: the extraction of ore in the current period and improved access to ore which will be extracted in future periods. When the cost of stripping which has a future benefit is not distinguishable from the cost of producing current inventories, the stripping cost is allocated to each of these activities based on a relevant production measure using a life-of-component strip ratio. The ratio divides the tonnage of waste mined for the component for the period either by the quantity of ore mined for the component or by the quantity of minerals contained in the ore mined for the component. In some operations, the quantity of ore is a more appropriate basis for allocating costs, particularly where there are significant by-products. Stripping costs for the component are deferred to the extent that the current period ratio exceeds the life of component ratio. The stripping activity asset is depreciated on a “units of production” basis based on expected production of either ore or minerals contained in the ore over the life of the component unless another method is more appropriate. The life-of-component ratios are based on the ore reserves of the mine (and for some mines, other mineral resources) and the annual mine plan; they are a function of the mine design and, therefore, changes to that design will generally result in changes to the ratios. Changes in other technical or economic parameters that impact the ore reserves (and for some mines, other mineral resources) may also have an impact on the life-of-component ratios even if they do not affect the mine design. Changes to the ratios are accounted for prospectively. It may be the case that subsequent phases of stripping will access additional ore and that these subsequent phases are only possible after the first phase has taken place. Where applicable, the Group considers this on a mine-by-mine basis. Generally, the only ore attributed to the stripping activity asset for the purposes of calculating a life-of-component ratio, and for the purposes of amortisation, is the ore to be extracted from the originally identified component. Deferred stripping costs are included in “Mining properties and leases” within “Property, plant and equipment” or within “Investments in equity accounted units”, as appropriate. Amortisation of deferred stripping costs is included in “Depreciation of property, plant and equipment” within “Net operating costs” or in “Share of profit after tax of equity accounted units”, as appropriate.
Depreciation of non-current assets	Depreciation of non-current assets Property, plant and equipment is depreciated over its useful life, or over the remaining life of the mine or smelter or refinery if that is shorter and there is no reasonable alternative use for the asset by the Group. The useful lives of the major assets of a CGU are often dependent on the life of the orebody to which they relate. Where this is the case, the lives of mining properties, and their associated refineries, concentrators and other long-lived processing equipment are generally limited to the expected life of the orebody. The life of the orebody, in turn, is estimated on the basis of the life-of-mine plan. Where the major assets of a CGU are not dependent on the life of a related orebody, management applies judgment in estimating the remaining service potential of long-lived assets. Factors affecting the remaining service potential of smelters include, for example, smelter technology and electricity purchase contracts when power is not sourced from the company’s, or in some cases a local government’s, renewably sourced electricity generating capacity. The useful lives and residual values for material assets and categories of assets are reviewed annually and changes are reflected prospectively. Depreciation commences when an asset is available for use. The major categories of property, plant and equipment are depreciated on a units of production and/or straight line basis as follows: Units of production basis For mining properties and leases and certain mining equipment, consumption of the economic benefits of the asset is linked to production. Except as noted below, these assets are depreciated on the units of production basis. In applying the units of production method, depreciation is normally calculated based on production in the period as a percentage of total expected production in current and future periods based on ore reserves and, for some mines, other mineral resources. Other mineral resources may be included in the calculations of total expected production in limited circumstances where there are very large areas of contiguous mineralisation, for which the economic viability is not sensitive to likely variations in grade, as may be the case for certain iron ore, bauxite and industrial minerals deposits and where there is a high degree of confidence that the other mineral resources can be extracted economically. This would be the case when the other mineral resources do not yet have the status of ore reserves merely because the necessary detailed evaluation work has not yet been performed and the responsible technical personnel agree that inclusion of a proportion of measured and indicated resources in the calculation of total expected production is appropriate based on historical reserve conversion rates. The required level of confidence is unlikely to exist for minerals that are typically found in low-grade ore (as compared with the above), such as copper or gold. In these cases, specific areas of mineralisation have to be evaluated in detail before their economic status can be predicted with confidence. Where measured and indicated resources are used in the calculation of depreciation for infrastructure, primarily rail and port, which will benefit current and future mines, then the measured and indicated resources may relate to mines which are currently in production or to mines where there is a high degree of confidence that they will be brought into production in the future. The quantum of mineral resources is determined taking into account future capital costs as required by the JORC code. The depreciation calculation, however, applies to current mines only and does not take into account future development costs for mines that are not yet in production. Measured and indicated resources are currently incorporated into depreciation calculations in the Group’s Australian iron ore business. Straight line basis Assets within operations for which production is not expected to fluctuate significantly from one year to another or which have a physical life shorter than the related mine are depreciated on a straight line basis.
Impairment charges/reversals of non-current assets	Impairment charges/reversals of non-current assets Impairment charges and reversals are assessed at the level of cash-generating units which, in accordance with IAS 36 “Impairment of Assets”, are identified as the smallest identifiable asset or group of assets that generate cash inflows, which are largely independent of the cash inflows from other assets. Separate CGUs are identified where an active market exists for intermediate products, even if the majority of those products are further processed internally. Impairment of financial assets is evaluated in accordance with IAS 39. In some cases, individual business units consist of several operations with independent cash-generating streams which constitute separate cash-generating units. Goodwill acquired through business combinations is allocated to the CGU or groups of CGUs that are expected to benefit from the related business combination, and tested for impairment at the lowest level within the Group at which goodwill is monitored for internal management purposes. All goodwill, intangible assets that have an indefinite life and intangible assets that are not ready for use are tested annually for impairment as at 30 September, regardless of whether there has been an impairment trigger or, more frequently, if events or changes in circumstances indicate a potential impairment. Property, plant and equipment and intangible assets with finite lives are reviewed for impairment if there is an indication that the carrying amount may not be recoverable. The Group conducts an internal review of the asset values annually as at 30 September which is used as a source of information to assess for indications of impairment or reversal of previously recognised impairment losses. External factors, such as changes in forecasted commodity prices, costs and other market factors as well as internal factors such as cancellation of a project or reduced project scope, are also monitored to assess for indications of impairment or reversal of previously recognised impairment losses. If any such indication exists then an impairment review is undertaken; the recoverable amount is assessed by reference to the higher of value in use (being the net present value of expected future cash flows of the relevant CGU in its current condition) and fair value less cost of disposal (FVLCD). When the recoverable amount of the CGU is measured by reference to FVLCD, this amount is further classified in accordance with the fair value hierarchy for observable market data that is consistent with the unit of account for the CGU being tested. The Group considers that the best evidence of FVLCD is the value obtained from an active market or binding sale agreement and, in this case, the recoverable amount is classified in the fair value hierarchy as level 1. When FVLCD is based on quoted prices for equity instruments but adjusted to reflect factors such as a lack of liquidity in the market, the recoverable amount is classified as level 2 in the fair value hierarchy. No CGUs are currently assessed for impairment by reference to a recoverable amount based on FVLCD classified as level 1 or level 2. Where unobservable inputs are material to the measurement of the recoverable amount, FVLCD is based on the best information available to reflect the amount the Group could receive for the CGU in an orderly transaction between market participants at the measurement date. This is often estimated using discounted cash flow techniques and is classified as level 3 in the fair value hierarchy. Where the recoverable amount is assessed using FVLCD based on discounted cash flow techniques, the resulting estimates are based on detailed life-of-mine and/or long-term production plans. These may include anticipated expansions which are at the evaluation stage of study. The cash flow forecasts for FVLCD purposes are based on management’s best estimates of expected future revenues and costs, including the future cash costs of production, capital expenditure, and closure, restoration and environmental costs. For the purposes of determining FVLCD from a market participant’s perspective, the cash flows incorporate management’s price and cost assumptions in the short and medium term. In the longer term, operating margins are assumed to remain constant where appropriate, as it is considered unlikely that a market participant would prepare detailed forecasts over a longer term. The cash flow forecasts may include net cash flows expected to be realised from the extraction, processing and sale of material that does not currently qualify for inclusion in ore reserves. Such non-reserve material is only included when there is a high degree of confidence in its economic extraction. This expectation is usually based on preliminary drilling and sampling of areas of mineralisation that are contiguous with existing ore reserves. Typically, the additional evaluation required to achieve reserves status for such material has not yet been done because this would involve incurring evaluation costs earlier than is required for the efficient planning and operation of the mine. As noted above, cost levels incorporated in the cash flow forecasts for FVLCD purposes are based on the current life-of-mine plan or long-term production plan for the CGU. This differs from value in use which requires future cash flows to be estimated for the asset in its current condition and therefore does not include future cash flows associated with improving or enhancing an asset’s performance. Anticipated enhancements to assets may be included in FVLCD calculations and, therefore, generally result in a higher value. Where the recoverable amount of a CGU is dependent on the life of its associated orebody, expected future cash flows reflect the current life of mine and/or long-term production plans, which are based on detailed research, analysis and iterative modelling to optimise the level of return from investment, output and sequence of extraction. The mine plan takes account of all relevant characteristics of the orebody, including waste-to-ore ratios, ore grades, haul distances, chemical and metallurgical properties of the ore impacting process recoveries and capacities of processing equipment that can be used. The life-of-mine plan and/or long-term production plans are, therefore, the basis for forecasting production output and production costs in each future year. Notes to the 2018 financial statements continued 1 Principal accounting policies continued Forecast cash flows for ore reserve estimation for JORC purposes are generally based on Rio Tinto’s commodity price forecasts, which assume short-term market prices will revert to the Group’s assessment of the long-term price, generally over a period of three to five years. For most commodities, these forecast commodity prices are derived from a combination of analyses of the marginal costs of the producers and of the incentive price of these commodities. These assessments often differ from current price levels and are updated periodically. The Group does not believe that published medium- and long-term forward prices necessarily provide a good indication of future levels because they tend to be strongly influenced by spot prices. The price forecasts used for ore reserve estimation are generally consistent with those used for impairment testing unless management deems that in certain economic environments, a market participant would not assume Rio Tinto’s view on prices, in which case in preparing FVLCD impairment calculations management estimates the assumptions that a market participant would be expected to use. Forecast future cash flows of a CGU take into account the sales prices under existing sales contracts. The discount rates applied to the future cash flow forecasts represent an estimate of the rate the market would apply having regard to the time value of money and the risks specific to the asset for which the future cash flow estimates have not been adjusted. The Group’s weighted average cost of capital is generally used as a starting point for determining the discount rates, with appropriate adjustments for the risk profile of the countries in which the individual CGUs operate, weighted for gold content. For final feasibility studies and ore reserve estimation, internal hurdle rates, which are generally higher than the Group’s weighted average cost of capital, are used. For developments funded with project finance, the debt component of the weighted average cost of capital may be calculated by reference to the specific interest rate of the project finance and anticipated leverage of the project. For operations with a functional currency other than the US dollar, the impairment review is undertaken in the relevant functional currency. In estimating FVLCD, internal forecasts of exchange rates take into account spot exchange rates, historical data and external forecasts, and are kept constant in real terms after five years. The great majority of the Group’s sales are based on prices denominated in US dollars. To the extent that the currencies of countries in which the Group produces commodities strengthen against the US dollar without an increase in commodity prices, cash flows and, therefore, net present values are reduced. Management considers that over the long term, there is a tendency for movements in commodity prices to compensate to some extent for movements in the value of the US dollar, particularly against the Australian dollar and Canadian dollar, and vice versa. However, such compensating changes are not synchronised and do not fully offset each other. In estimating value in use, the present value of future cash flows in foreign currencies is translated at the spot exchange rate on the testing date. Non-current assets (excluding goodwill) that have suffered impairment are reviewed using the same basis for valuation as explained above whenever events or changes in circumstances indicate that the impairment loss may no longer exist, or may have decreased. If appropriate, an impairment reversal will be recognised. The carrying amount of the CGU after reversal must be the lower of (a) the recoverable amount, as calculated above, and (b) the carrying amount that would have been determined (net of amortisation or depreciation) had no impairment loss been recognised for the CGU in prior periods. An onerous contract is defined under IAS 37 “Provisions, Contingent Liabilities and Contingent Assets” as a contract under which the unavoidable costs of meeting the obligations under the contract exceed the economic benefits expected to be received under it. Provision is made when the assets dedicated to the contract are fully impaired or the contract becomes stranded as a result of a business decision.
Determination of ore reserve and mineral resource estimates	(j) Determination of ore reserve and mineral resource estimates The Group estimates its ore reserves and mineral resources based on information compiled by Competent Persons as defined in accordance with the JORC code. Ore reserves and, for certain mines, other mineral resources determined in this way are used in the calculation of depreciation, amortisation and impairment charges and for forecasting the timing of the payment of close-down and restoration costs and the recovery of deferred tax assets. The depreciation and impairment policy above notes instances in which mineral resources are taken into account for accounting purposes. In addition, value may be attributed to mineral resources in purchase price allocations undertaken for the purposes of business combination accounting.
Close-down, restoration and environmental obligations	(k) Close-down, restoration and environmental obligations (note 26) The Group has provisions for close-down and restoration costs which include the dismantling and demolition of infrastructure, the removal of residual materials and the remediation of disturbed areas for mines and certain refineries and smelters. These provisions are based on all regulatory requirements and any other commitments made to stakeholders. Closure provisions are not made for those operations that have no known restrictions on their lives as the closure dates cannot be reliably estimated. This applies primarily to certain Canadian smelters which have indefinite-lived water rights or power agreements for renewably sourced power with local governments. Close-down and restoration costs are a normal consequence of mining or production, and the majority of close-down and restoration expenditure is incurred in the years following closure of the mine, refinery or smelter. Although the ultimate cost to be incurred is uncertain, the Group’s businesses estimate their costs using current restoration standards and techniques. Close-down and restoration costs are provided for in the accounting period when the obligation arising from the related disturbance occurs, based on the net present value of the estimated future costs of restoration to be incurred during the life of the operation and post-closure. Where appropriate, the provision is estimated using probability weighting of the different remediation and closure scenarios. The obligation may occur during development or during the production phase of a facility. Provisions for close-down and restoration costs do not include any additional obligations that are expected to arise from future disturbance. The costs are estimated on the basis of a closure plan, and are reviewed at each reporting period during the life of the operation to reflect known developments. The estimates are also subject to formal review, with appropriate external support, at regular intervals. The initial close-down and restoration provision is capitalised within “Property, plant and equipment”. Subsequent movements in the close-down and restoration provisions for ongoing operations, including those resulting from new disturbance related to expansions or other activities qualifying for capitalisation, updated cost estimates, changes to the estimated lives of operations, changes to the timing of closure activities and revisions to discount rates are also capitalised within “Property, plant and equipment”. These costs are then depreciated over the lives of the assets to which they relate. Changes in closure provisions relating to closed operations are charged/credited to “Net operating costs” in the income statement. Where rehabilitation is conducted systematically over the life of the operation, rather than at the time of closure, provision is made for the estimated outstanding continuous rehabilitation work at each balance sheet date and the cost is charged to the income statement. The amortisation or “unwinding” of the discount applied in establishing the provisions is charged to the income statement in each accounting period. The amortisation of the discount is shown within “Finance items” in the income statement. Environmental costs result from environmental damage that was not a necessary consequence of operations, and may include remediation, compensation and penalties. Provision is made for the estimated present value of such costs at the balance sheet date. These costs are charged to “Net operating costs”, except for the unwinding of the discount, which is shown within “Finance items”. Remediation procedures may commence soon after the time the disturbance, remediation process and estimated remediation costs become known, but can continue for many years depending on the nature of the disturbance and the remediation techniques used.
Inventories	(l) Inventories (note 16) Inventories are valued at the lower of cost and net realisable value, primarily on a weighted average cost basis. Average costs are calculated by reference to the cost levels experienced in the relevant month together with those in opening inventory. The cost of raw materials and consumable stores is the purchase price. The cost of partly-processed and saleable products is generally the cost of production, including: – Labour costs, materials and contractor expenses which are directly attributable to the extraction and processing of ore or the production of alumina and aluminium – The depreciation of mining properties and leases and of property, plant and equipment used in the extraction and processing of ore or the production of alumina and aluminium – Production overheads Work in progress includes ore stockpiles and other partly processed material. Stockpiles represent ore that has been extracted and is available for further processing. If there is significant uncertainty as to if and/or when the stockpiled ore will be processed, the ore is expensed as mined. If the ore will not be processed within 12 months after the balance sheet date, it is included within non-current assets and net realisable value is calculated on a discounted cash flow basis. Quantities of stockpiled ore are assessed primarily through surveys and assays. Certain estimates, including expected metal recoveries, are calculated using available industry, engineering and scientific data, and are periodically reassessed taking into account technical analysis and historical performance.
Taxation	(m) Taxation (note 9 and note 17) Current tax is the tax expected to be payable on the taxable income for the year calculated using rates that have been enacted or substantively enacted at the balance sheet date. It includes adjustments for tax expected to be payable or recoverable in respect of previous periods. Where the amount of tax payable or recoverable is uncertain, Rio Tinto establishes provisions based on the Group’s judgment of the most likely amount of the liability, or recovery. Deferred tax is calculated in accordance with IAS 12. The Group provides for deferred tax in respect of fair value adjustments on acquisitions including mining rights that, in general, are not eligible for income tax allowances. Provision for deferred tax is based on the difference between the carrying value of the asset and its income tax base (which may be nil). Even when there is no income tax base, the existence of a tax base for capital gains tax purposes is not usually taken into account in determining the deferred tax provision for the assets, unless they are classified as held for sale or it is determined for other reasons that the carrying amount is expected to be recovered primarily through disposal and not through use of the assets.
Post-employment benefits	(n) Post-employment benefits (note 44) The Group operates a number of defined benefit plans which provide lump sums, pensions, medical benefits and life insurance to retirees. In accordance with IAS 19, for post-employment defined benefit plans, the difference between the fair value of any plan assets and the present value of the plan obligations is recognised as an asset or liability in the balance sheet. Where appropriate, the recognition of assets may be restricted to the present value of any amounts the Group expects to recover by way of refunds from the plan or reductions in future contributions. In determining the extent to which a refund will be available the Group considers whether any third party, such as a trustee or pension committee, has the power to enhance benefits or to wind up a pension plan without the Group’s consent. The most significant assumptions used in accounting for pension plans are the discount rate, the inflation rate and mortality rates. The discount rate is used to determine the net present value of the obligations, the interest cost on the obligations and the interest income on plan assets. The discount rate used is the yield on high-quality corporate bonds with maturities and terms that match those of the post-employment obligations as closely as possible. Where there is no developed corporate bond market in a currency, the rate on government bonds is used. The inflation rate is used to project increases in future benefit payments for those plans that have benefits linked to inflation. The mortality rates are used to project the period over which benefits will be paid, which is then discounted to arrive at the net present value of the obligations. The current service cost, any past service cost and the effect of any curtailment or settlements are recognised in the income statement. The interest cost less interest income on assets held in the plans is also charged to the income statement. All amounts charged to the income statement in respect of these plans are included within “Net operating costs” or in “Share of profit after tax of equity accounted units”, as appropriate. The Group’s contributions to defined contribution plans are charged to the income statement in the period to which the contributions relate. These are included within “Net operating costs” or in “Share of profit after tax of equity accounted units”, as appropriate.
Cash and cash equivalents	(o) Cash and cash equivalents (note 21) For the purpose of the balance sheet, cash and cash equivalents comprise: cash on hand, deposits held with banks, and short-term, highly liquid investments (mainly money market funds) that are readily convertible into known amounts of cash and which are subject to insignificant risk of changes in value. Bank overdrafts are shown as current liabilities in the balance sheet. Further detail on cash and cash equivalents, including restricted cash, is shown in note 21. For the purposes of the cash flow statement, cash and cash equivalents are net of bank overdrafts that are repayable on demand.
Financial instruments	(p) Financial instruments (note 30) The Group has elected to apply the limited exemption in IFRS 9 relating to classification, measurement and impairment requirements for financial instruments, and accordingly comparative periods have not been restated and remain in line with the previous standard IAS 39 “Financial Instruments: Recognition and Measurement”. For further understanding of the impact of the transition to IFRS 9, refer to note 45. (i) Financial assets Classification and measurement The Group classifies its financial assets into the following categories: those to be measured subsequently at fair value (either through other comprehensive income (FVOCI) or through the income statement (FVPL)) and those to be held at amortised cost. Classification depends on the business model for managing the financial assets and the contractual terms of the cash flows. Management determines the classification of financial assets at initial recognition. The Group’s policy with regard to financial risk management is set out in note 30. Generally, the Group does not acquire financial assets for the purpose of selling in the short term. The Group’s business model is primarily that of “hold to collect” (where assets are held in order to collect contractual cash flows). When the Group enters into derivative contracts, these transactions are designed to reduce exposures relating to assets and liabilities, firm commitments or anticipated transactions. (a) Financial assets held at amortised cost This classification applies to debt instruments which are held under a hold to collect business model and which have cash flows that meet the ‘’solely payments of principal and interest’’ (SPPI) criteria. At initial recognition, trade receivables that do not have a significant financing component, are recognised at their transaction price. Other financial assets are initially recognised at fair value plus related transaction costs; they are subsequently measured at amortised cost using the effective interest method. Any gain or loss on derecognition or modification of a financial asset held at amortised cost is recognised in the income statement. (b) Financial assets held at fair value through other comprehensive income (FVOCI) This classification applies to the following financial assets: – Debt instruments that are held under a business model where they are held for the collection of contractual cash flows and also for sale (“collect and sell”) and which have cash flows that meet the SPPI criteria. An example would be where trade receivable invoices for certain customers were factored from time to time. All movements in the fair value of these financial assets are taken through other comprehensive income, except for the recognition of impairment gains or losses, interest revenue (including transaction costs by applying the effective interest method), gains or losses arising on derecognition and foreign exchange gains and losses which are recognised in the income statement. When the financial asset is derecognised, the cumulative fair value gain or loss previously recognised in other comprehensive income is reclassified to the income statement. – Equity investments where the Group has irrevocably elected to present fair value gains and losses on revaluation in other comprehensive income. The election can be made for each individual investment; however, it is not applicable to equity investments held for trading. Fair value gains or losses on revaluation of such equity investments, including any foreign exchange component, are recognised in other comprehensive income. When the equity investment is derecognised, there is no reclassification of fair value gains or losses previously recognised in other comprehensive income to the income statement. Dividends are recognised in the income statement when the right to receive payment is established. (c) Financial assets held at fair value through profit or loss (FVPL) This classification applies to the following financial assets. In all cases, transaction costs are immediately expensed to the income statement. – Debt instruments that do not meet the criteria of amortised cost or fair value through other comprehensive income. The Group has a significant proportion of trade receivables with embedded derivatives for provisional pricing. These receivables are generally held to collect but do not meet the SPPI criteria and as a result must be held at FVPL. Subsequent fair value gains or losses are taken to the income statement. – Equity investments which are held for trading or where the FVOCI election has not been applied. All fair value gains or losses and related dividend income are recognised in the income statement. – Derivatives which are not designated as a hedging instrument. All subsequent fair value gains or losses are recognised in the income statement. (ii) Financial liabilities Borrowings and other financial liabilities (including trade payables but excluding derivative liabilities) are recognised initially at fair value, net of transaction costs incurred, and are subsequently measured at amortised cost. The Group participates in supply chain finance arrangements whereby vendors may elect to receive early payment of their invoice from a bank by factoring their receivable from Rio Tinto. These arrangements do not modify the terms of the original liability, and therefore financial liabilities subject to supply chain finance continue to be classified as trade payables. (iii) Impairment of financial assets A forward-looking expected credit loss (ECL) review is required for: debt instruments measured at amortised cost or held at fair value through other comprehensive income; loan commitments and financial guarantees not measured at fair value through profit or loss; lease receivables and trade receivables that give rise to an unconditional right to consideration. As permitted by IFRS 9, the Group applies the “simplified approach” to trade receivable balances and the “general approach” to all other financial assets. The general approach incorporates a review for any significant increase in counterparty credit risk since inception. The ECL reviews include assumptions about the risk of default and expected loss rates. For trade receivables, the assessment takes into account the use of credit enhancements, for example, letters of credit. Impairments for undrawn loan commitments are reflected as a provision. (iv) Derivatives and hedge accounting The Group applies the hedge accounting requirements under IFRS 9 and its hedging activities are discussed in note 30 with movements on hedging reserves disclosed in note 29. Where applicable, the Group may defer the costs of hedging including currency basis spreads, forward points and the time value of options.
Share-based payments	(q) Share-based payments (note 43) The fair value of the Group’s share plans is recognised as an expense over the expected vesting period with an offset to retained earnings for Rio Tinto plc plans and to other reserves for Rio Tinto Limited plans. The Group uses fair values provided by independent actuaries calculated using either a lattice-based option valuation model or a Monte Carlo simulation model. The terms of each plan are considered at the balance sheet date to determine whether the plan should be accounted for as equity-settled or cash-settled. The Group does not operate any plans as cash-settled. However, the Performance Share Plan can, at the discretion of the directors, offer employees an equivalent amount in cash. This is not standard practice. In some jurisdictions, employees are granted cash-settled awards where equity-settled awards are prohibited by local laws and regulations. The value of these awards is immaterial. The Group’s equity-settled share plans are settled either by: the issuance of shares by the relevant parent company; the purchase of shares on market; or the use of shares held in treasury which were previously acquired as part of a share buy-back. If the cost of shares acquired to satisfy the plans differs from the expense charged, the difference is taken to retained earnings or other reserves, as appropriate.
Share capital	(r) Share capital (notes 27 and 28) Ordinary shares are classified as equity. Incremental costs directly attributable to the issuance of new shares are shown in equity as a deduction, net of tax, from the proceeds. Where any Group company purchases the Group’s equity share capital (treasury shares), the consideration paid, including any directly attributable incremental costs (net of income taxes) is deducted from equity attributable to owners of Rio Tinto. Where such shares are subsequently reissued, any consideration received, net of any directly attributable incremental costs and the related income tax effects, is included in equity attributable to owners of Rio Tinto. If purchased Rio Tinto plc shares are cancelled, an amount equal to the nominal value of the cancelled share is credited to the capital redemption reserve.
Segment reporting	(s) Segment reporting (notes 2 and 3) Operating segments are reported in a manner consistent with the internal reporting provided to the chief operating decision maker (CODM). The Group considers that Rio Tinto’s chief executive is the CODM, who is responsible for allocating resources and assessing performance of the operating segments.

Principal accounting policies_2

Principal accounting policies (Table)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Accounting Policies [Abstract]
Summary of significant differences between lease commitments and lease liability recorded on transition	US$bn Operating lease commitments under IAS 17 per note 31 1.7 Exclude/deduct Leases expiring in 12 months or fewer (a) (0.1) Committed leases not commenced (a) (0.1) Components excluded from the lease liability (a) (0.2) Include/add Cost of reasonably certain extensions (a) 0.3 Other (b) 0.1 Sub total 1.7 Effect of discounting on payments included in the calculation of the lease liability (excluding finance lease balances) (0.4) Lease liability opening balance reported as at 1 January 2019 (IFRS 16) 1.3 (a) Undiscounted. (b) Includes finance lease liabilities already reported under IAS 17. Refer to note 23.

Operating segments (Tables)

Operating segments (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Operating Segments [Abstract]
Summary of operating segments	The financial information by business unit provided on pages 249 to 251 of these financial statements provides additional voluntary disclosure which the Group considers useful to the users of the financial statements. 2018 2017 2016 Gross sales revenue US$m US$m US$m Iron Ore 18,485 18,251 14,605 Aluminium 12,191 11,005 9,458 Copper & Diamonds 6,468 4,842 4,524 Energy & Minerals 5,697 7,764 6,734 Other Operations 9 10 8 Reportable segments total 42,850 41,872 35,329 Inter-segment transactions (15 ) (15 ) (11 ) Product group total 42,835 41,857 35,318 Items excluded from underlying earnings - 10 18 Gross sales revenue 42,835 41,867 35,336 Share of equity accounted unit sales and adjustments for intra-subsidiary/equity accounted units sales (2,313 ) (1,837 ) (1,555 ) Consolidated sales revenue per income statement 40,522 40,030 33,781 Gross sales revenue includes the Group’s proportionate share of sales revenue of equity accounted units (after adjusting for sales to subsidiaries) of US$2,354 million (2017: US$1,859 million; 2016: US$1,585 million) which are not included in consolidated sales revenue. Consolidated sales revenue includes subsidiary sales of US$41 million (2017: US$22 million; 2016: US$30 million) to equity accounted units which are not included in gross sales revenue. 2018 2017 2016 Capital expenditure US$m US$m US$m Iron Ore 1,288 1,201 868 Aluminium 1,373 1,436 916 Copper & Diamonds 2,150 1,622 1,441 Energy & Minerals 456 467 141 Other Operations 12 (35 ) (11 ) Reportable segments total 5,279 4,691 3,355 Other items 65 70 (46 ) Less: capital expenditure of equity accounted units (500 ) (417 ) (651 ) Capital expenditure per financial information by business unit 4,844 4,344 2,658 Add back: proceeds from disposal of property, plant and equipment 586 138 354 Capital expenditure per cash flow statement 5,430 4,482 3,012 Capital expenditure for reportable segments comprises the net cash outflow on purchases less disposals of property, plant and equipment, capitalised evaluation costs and purchases less disposals of other intangible assets. The details provided include 100% of subsidiaries’ capital expenditure and Rio Tinto’s share of the capital expenditure of joint operations and equity accounted units. 2018 2017 2016 Depreciation and amortisation US$m US$m US$m Iron Ore 1,682 1,645 1,645 Aluminium 1,122 1,199 1,250 Copper & Diamonds 1,317 1,452 1,601 Energy & Minerals 475 652 739 Other Operations 26 32 34 Reportable segments total 4,622 4,980 5,269 Other items 43 42 51 Less: depreciation and amortisation of equity accounted units (650 ) (647 ) (526 ) Depreciation and amortisation per note 4 4,015 4,375 4,794 Product group depreciation and amortisation for reportable segments totals include 100% of subsidiaries’ depreciation and amortisation and Rio Tinto’s share of the depreciation and amortisation of equity accounted units. Rio Tinto’s share of the depreciation and amortisation charge of equity accounted units is deducted to arrive at depreciation and amortisation, excluding equity accounted units, as shown in note 4. These figures exclude impairment charges and reversals, which are excluded from underlying earnings. 2018 2017 2016 Tax charge/(credit) US$m US$m US$m Iron Ore 2,819 2,871 2,005 Aluminium 532 543 171 Copper & Diamonds 118 48 (320 ) Energy & Minerals 511 652 331 Other Operations (51 ) (84 ) (73 ) Reportable segments total 3,929 4,030 2,114 Other items (276 ) (261 ) (191 ) Exploration and evaluation not attributed to product groups (38 ) (36 ) (27 ) Net finance costs (174 ) (364 ) (484 ) 3,441 3,369 1,412 Tax charge excluded from underlying earnings 801 596 155 Tax charge per income statement 4,242 3,965 1,567 Tax charge/(credit) excludes amounts relating to equity accounted units. Further information on the tax charge/(credit) excluded from underlying earnings is provided in the section “Underlying earnings”, below. 2018 2017 2016 Underlying EBITDA US$m US$m US$m Iron Ore 11,325 11,520 8,526 Aluminium 3,095 3,423 2,472 Copper & Diamonds 2,776 1,904 1,387 Energy & Minerals 2,193 2,803 1,806 Other Operations (70 ) (116 ) (95 ) Reportable segments total 19,319 19,534 14,096 Central pension costs, share-based payments and insurance (128 ) (68 ) (34 ) Restructuring, project and one-off costs (272 ) (177 ) (13 ) Central costs (552 ) (491 ) (364 ) Exploration and evaluation not attributed to product groups (231 ) (218 ) (175 ) Underlying EBITDA 18,136 18,580 13,510 Items excluded from underlying EBITDA 5,127 1,912 (687 ) EBITDA 23,263 20,492 12,823 Depreciation, amortisation and impairment charges in subsidiaries and equity accounted units (4,691 ) (5,746 ) (5,466 ) Taxation and finance items in equity accounted units (372 ) (272 ) (241 ) Profit on ordinary activities before finance items and tax 18,200 14,474 7,116 Notes to the 2018 financial statements continued 2 Operating segments continued 2018 2017 2016 Underlying earnings US$m US$m US$m Iron Ore 6,514 6,692 4,611 Aluminium 1,347 1,583 947 Copper & Diamonds 1,054 263 (18 ) Energy & Minerals 1,012 1,242 612 Other Operations (102 ) (138 ) (88 ) Reportable segments total 9,825 9,642 6,064 Central pension costs, share-based payments and insurance (90 ) (48 ) (24 ) Restructuring, project and one-off costs (190 ) (124 ) (9 ) Central costs (410 ) (311 ) (208 ) Exploration and evaluation not attributed to product groups (193 ) (178 ) (147 ) Net finance costs (134 ) (354 ) (576 ) Underlying earnings 8,808 8,627 5,100 Items excluded from underlying earnings 4,830 135 (483 ) Net earnings attributable to owners of Rio Tinto per income statement 13,638 8,762 4,617 Reconciliation of net earnings/(losses) to underlying earnings Non- controlling Net Net Net Pre-tax (m) Taxation interests amount amount amount 2018 2018 2018 2018 2017 2016 Exclusions from underlying earnings US$m US$m US$m US$m US$m US$m Impairment charges (note 6) (132 ) 25 3 (104 ) (481 ) (183 ) Net gains on consolidation and disposal of interests in businesses (a) 4,622 (626 ) - 3,996 2,022 382 Exchange and derivative gains/(losses): – Exchange gains/(losses) on US dollar net debt, intragroup balances and derivatives (b) 694 (136 ) (8 ) 550 (488 ) 516 – (Losses)/gains on currency and interest rate derivatives not qualifying for hedge accounting (c) (59 ) 11 - (48 ) 30 (12 ) – Gains/(losses) on embedded commodity derivatives not qualifying for hedge accounting (d) 288 (83 ) (3 ) 202 (352 ) 32 Losses from increases to closure estimates (non-operating and fully impaired sites) (e) (376 ) 41 - (335 ) - (282 ) Gain relating to surplus land at Kitimat (f) 602 (33 ) - 569 - - Changes in corporate tax rates in the US and France (g) - - - - (439 ) - Onerous port and rail contracts (h) - - - - - (329 ) Restructuring costs and global headcount reductions - - - - - (177 ) Rio Tinto Kennecott insurance settlement (i) - - - - 45 - Tax provision (j) - - - - - (380 ) Tax charge relating to expected divestments (k) - - - - (202 ) - Other exclusions (l) - - - - - (50 ) Total excluded from underlying earnings 5,639 (801 ) (8 ) 4,830 135 (483 ) Net earnings 18,167 (4,242 ) (287 ) 13,638 8,762 4,617 Underlying earnings 12,528 (3,441 ) (279 ) 8,808 8,627 5,100 (a) On 10 May 2018, Rio Tinto and Alcoa announced they had launched a new joint venture, Elysis, to develop and commercialise a carbon-free aluminium smelting process. Rio Tinto’s interest in the joint venture In 2017, the net gain related mainly to the sale of Coal & Allied Industries Limited, which completed on 1 September 2017. In 2016, the net gain related mainly to the sale of Rio Tinto’s 40% interest in the Bengalla Joint Venture on 1 March 2016 and the sale of the Lochaber assets in Scotland on 23 November 2016. This was partially offset by a loss on disposal of the 100% interest in Carbone Savoie on 31 March 2016. (b) Exchange gains/(losses) on external US dollar net debt and intragroup balances comprise of post-tax foreign exchange losses on US dollar denominated net debt in non-US dollar functional currency companies of US$386 million loss and post-tax gains of US$936 million on intragroup balances, primarily as a result of the Australian and Canadian dollars both weakening against the US dollar. Net exchange gains in 2017 comprise post-tax foreign exchange gains of US$420 million on US dollar denominated net debt, and US$908 million losses on intragroup balances. Net exchange gains in 2016 comprise post-tax foreign exchange gains of US$123 million on external US dollar denominated net debt, and US$393 million gains on intragroup balances, mainly as the Canadian dollar strengthened against the US dollar. (c) Valuation changes on currency and interest rate derivatives, which are ineligible for hedge accounting, other than those embedded in commercial contracts, and the currency revaluation of embedded US dollar derivatives contained in contracts held by entities whose functional currency is not the US dollar. (d) Valuation changes on derivatives, embedded in commercial contracts, that are ineligible for hedge accounting, but for which there will be an offsetting change in future Group earnings. From 1 January 2018, all mark-to-market movements on commodity derivatives entered into with the commercial objective of achieving spot pricing for the underlying transaction at the date of settlement are now included within underlying earnings. In 2017 and previous years, valuation changes on this type of commodity derivative were excluded from underlying earnings. The impact of this change on the reported comparatives is insignificant, and therefore the comparatives have not been restated. (e) been recognised in the income statement. The impairment charge in respect of Argyle recognised in 2017 (see note 6) was based on preliminary findings from the prefeasibility study. On this basis, the charge arising from the finalisation of this study in 2018 of US$134 million (US$93 million after tax) has been excluded from underlying earnings. On 6 December 2018, Energy Resources of Australia (ERA) (68% owned by Rio Tinto and listed on the Australian Stock Exchange) announced a likely increase to its closure provision of A$296 million pending finalisation of the Ranger Project Area closure feasibility study. The final assessment has indicated an increase equivalent to US$242 million. As the assets of ERA have been fully impaired, this increase has not been capitalised and has instead been recognised in the income statement. There is no tax impact in respect of this item. In 2016, the closure provision for non-operating and legacy operations increased mainly due to the Gove alumina refinery in Northern Territory, Australia where operations have been curtailed since May 2014. The provision was updated based on the cost estimates from the studies. Future revisions to the closure cost estimate during the study periods (including the next stage of feasibility study) will continue to be excluded from underlying earnings as the site operating assets have been fully impaired. (f) In November 2018, Rio Tinto completed the lease and sale of a wharf and land in Kitimat. This resulted in a pre-tax gain of US$549 million on disposal of Property, plant and equipment and Other income of US$53 million (total impact of US$569 million after tax). This has been excluded from underlying earnings on the grounds of materiality. (g) In 2017, deferred tax assets were remeasured to reflect lower corporate income tax rates in the US and France as a result of tax legislation changes substantively enacted in December 2017. (h) In 2016, a review of the infrastructure capacity requirements in Queensland, Australia, confirmed that it was no longer likely that Rio Tinto would utilise the Abbot Point Coal Terminal and associated rail infrastructure capacity contracted under take or pay arrangements, and agreement was reached with Adani, the owner of the port, to relinquish that capacity. Accordingly, an onerous contract provision was recognised based on the net present value of expected future cash flows for the port and rail capacity discounted at a post-tax real rate of 2%, resulting in a post-tax onerous contract charge of US$329 million. (i) In 2017, Rio Tinto received the final settlement on the insurance claims related to the 2013 slide at Rio Tinto Kennecott’s Bingham Canyon mine. The amounts excluded from underlying earnings were consistent with the previous excluded losses to which they related, in line with the treatment of the 2013 and 2015 settlement payments. (j) Tax provision includes amounts provided for specific tax matters for which the timing of resolution and potential economic outflow are uncertain. During 2016, provision was made in relation to matters under discussion with the Australian Taxation Office (ATO) in relation to the transfer pricing of certain transactions between Rio Tinto entities based in Australia and the Group’s commercial centre in Singapore for the period since 2009. (k) In 2017, deferred tax assets were derecognised as a result of revised profit forecasts in France due to the expected divestments of Dunkerque and ISAL. The Dunkerque divestment completed in 2018. (l) Other credits and charges that, individually, or in aggregate if of similar type, are of a nature or size to require exclusion in order to provide additional insight into underlying business performance. In 2016, other exclusions included costs related to multiple transformation projects and the recuperation of capital losses against capital gains on divestment. (m) Exclusions from underlying earnings relating to equity accounted units are stated after tax and are included in the column “Pre-tax”.

Operating segments - addition_2

Operating segments - additional information (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Operating Segments [Abstract]
Summary of geographical location sales revenue and non-current assets other than excluded items	2018 2017 2016 2018 2017 2016 Consolidated sales revenue by destination (a) % % % US$m US$m US$m China 44.6 44.2 43.6 18,061 17,706 14,742 Asia (excluding China and Japan) 11.5 12.8 13.9 4,665 5,108 4,692 United States of America 15.5 14.3 13.9 6,278 5,716 4,709 Japan 9.6 11.7 11.3 3,873 4,701 3,809 Europe (excluding UK) 9.1 7.5 7.6 3,706 3,015 2,579 Canada 3.2 2.8 3.0 1,340 1,111 1,024 Australia 1.8 1.8 2.0 720 710 675 UK 1.0 1.1 1.2 386 449 391 Other countries 3.7 3.8 3.5 1,493 1,514 1,160 Consolidated sales revenue 100.0 100.0 100.0 40,522 40,030 33,781 (a) Consolidated sales revenue by geographical destination is based on the ultimate country of destination of the product, if known. If the eventual destination of the product sold through traders is not known then revenue is allocated to the location of the product at the time when control is transferred. Rio Tinto is domiciled in both the UK and Australia. Non-current assets other than excluded items (a) The total of non-current assets other than items excluded is shown by location below. This is allocated based on the location of the business units holding the assets. Adjusted (b) 2018 2017 US$m US$m Australia 28,592 32,890 Canada 13,775 14,822 Mongolia 9,912 8,582 United States of America 4,815 4,812 Africa 3,476 3,781 South America 3,047 3,304 Indonesia - 1,458 Europe (excluding France and the UK) 50 362 UK 59 66 France 79 94 Other countries 850 892 64,655 71,063 Non-current assets excluded from analysis above: Deferred tax assets 3,137 3,395 Other financial assets (including loans to equity accounted units) 814 510 Quasi equity loans to equity accounted units (c) 129 159 Tax recoverable 8 30 Trade and other receivables 1,304 1,397 Total non-current assets per balance sheet 70,047 76,554 (a) Allocation of non-current assets by country is based on the location of the business units holding the assets. It includes investments in equity accounted units totalling US$4,170 million (2017: US$4,327 million) which represents the Group’s share of net assets excluding quasi equity loans shown separately within “Loans to equity accounted units” above. (b) The 2017 comparatives above have been amended to correct the allocation of non-current assets other than excluded items by location. The impact is an increase in the amounts allocated to Canada and a decrease to the amounts allocated to France of US$182 million. There is no impact on the total non-current assets. (c) Loans to equity accounted units comprise quasi equity loans of US$129 million (2017: US$159 million) included in “Investments in equity accounted units” on the face of the balance sheet and non-current non-quasi equity loans of US$38 million (2017: US$39 million) shown within “Other financial assets”.
Consolidated sales revenue by product	Consolidated sales revenue by product Consolidated sales revenues of the Group are derived from the following products sold to external customers: Revenue from contracts with customers Other revenue (a) Consolidated sales revenue Consolidated sales revenue Consolidated sales revenue 2018 2018 2018 2017 2016 US$m US$m US$m US$m US$m Iron ore 19,888 (21 ) 19,867 20,010 15,855 Aluminium 12,041 (22 ) 12,019 10,864 9,342 Copper 2,420 (32 ) 2,388 1,760 1,609 Coal 986 3 989 2,822 2,567 Industrial minerals 2,093 - 2,093 2,060 1,954 Gold 869 - 869 378 608 Diamonds 695 - 695 706 613 Other 1,602 - 1,602 1,430 1,233 Consolidated sales revenue 40,594 (72 ) 40,522 40,030 33,781 Share of equity accounted unit sales and intra-subsidiary/equity accounted unit sales 2,313 1,837 1,555 Gross sales revenue 42,835 41,867 35,336 (a) Certain of the Group’s products may be provisionally priced at the date revenue is recognised. The change in value of the provisionally priced receivables is based on relevant forward market prices and is included in “Other revenue” above. In prior periods there was no equivalent requirement under IAS 18 to separate out such provisional price movements and therefore this was not separately disclosed.

Net operating costs (excludin_2

Net operating costs (excluding items shown separately) (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Net Operating Costs Excluding Items Shown Separately [Abstract]
Summary of net operating costs (excluding items shown separately)	2018 2017 2016 Note US$m US$m US$m Raw materials, consumables, repairs and maintenance 10,613 9,286 8,760 Amortisation of intangible assets 13 133 177 227 Depreciation of property, plant and equipment 14 3,882 4,198 4,567 Employment costs 5 4,728 4,765 4,881 Shipping and other freight costs (a) 2,580 2,338 1,454 (Increase)/decrease in finished goods and work in progress (186 ) (82 ) 87 Royalties 2,117 2,228 1,889 Amounts charged by equity accounted units (b) 1,200 980 1,184 Net foreign exchange (gains)/losses (56 ) 61 38 Other external costs (a) (c) 3,184 3,967 3,512 Gain on sale of property, plant and equipment (d) (506 ) (32 ) (40 ) Provisions (including exchange differences on provisions) 26 1,011 527 1,404 Research and development 45 58 60 Costs included above qualifying for capitalisation (589 ) (486 ) (521 ) Other operating income (1,041 ) (1,002 ) (703 ) Net operating costs (excluding items shown separately) 27,115 26,983 26,799 (a) Net operating costs includes operating lease expense of US$787 million (2017: US$555 million, 2016: US$541 million). Costs for leases of dry bulk vessels (which include costs for crewing services) are included within “Shipping and other freight costs” and other lease costs are included within “Other external costs”. The Group will implement IFRS 16 “Leases” as at 1 January 2019; refer to note 1. (b) Amounts charged by equity accounted units relate to toll processing and also include purchases from equity accounted units of bauxite and aluminium which are then processed by the product group or sold to third parties. Generally, purchases are in proportion to the Group’s share of the equity accounted unit but in 2018, US$332 million (2017: US$229 million; 2016: US$383 million) related to purchases of the other investors’ share of production. (c) In 2017, other external costs include a financial penalty of £27.4 million (US$36.4 million) paid to the United Kingdom’s Financial Conduct Authority (FCA) in relation to the timing of the impairment of the Group’s former coal operations in Mozambique. Refer to note 31 for further detail. (d) Includes a pre-tax gain of US$549 million from the sale of property, plant and equipment at Kitimat. Refer to note 2.

Employment costs (Tables)

Employment costs (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Employee Cost Explanatory [Abstract]
Summary of employment costs	2018 2017 2016 Note US$m US$m US$m Total employment costs – Wages and salaries 4,154 4,129 4,235 – Social security costs 336 337 429 – Net post-retirement charge 44 532 500 522 – Share-based payment charge 43 122 91 116 5,144 5,057 5,302 Less: charged within provisions (a) 26 (416 ) (292 ) (421 ) Total employment costs 4 4,728 4,765 4,881 (a) Amounts included above in respect of provisions for pensions, post-retirement healthcare, long service leave and other employee entitlements which are included in “Provisions (including exchange differences on provisions)” in note 4.

Impairment charges (Tables)

Impairment charges (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Impairment Loss Recognised Or Reversed [Abstract]
Summary of impairment charges	Non- controlling Net Pre-tax Pre-tax Pre-tax Taxation interests amount amount amount 2018 2018 2018 2018 2017 2016 Note US$m US$m US$m US$m US$m US$m Aluminium – (123 ) 25 - (98 ) - - Energy & Minerals – Rössing (9 ) - 3 (6 ) (267 ) - Energy & Minerals – Roughrider - - - - (357 ) - Copper & Diamonds – Argyle - - - - (172 ) (241 ) Other - - - - - (8 ) Total impairment charge (132 ) 25 3 (104 ) (796 ) (249 ) Allocated as: Goodwill 12 - - - Intangible assets 13 (2 ) (357 ) (1 ) Property, plant and equipment 14 (130 ) (435 ) (248 ) Other assets and liabilities - (4 ) - Total impairment charge (132 ) (796 ) (249 ) Comprising: Total impairment charge net of reversals in the financial information by business unit ( page 249 (132 ) (796 ) (249 ) Taxation (including related to EAUs) 25 141 66 Non-controlling interests 3 174 - Total impairment in the income statement (104 ) (481 ) (183 )

Share of profit after tax of _2

Share of profit after tax of equity accounted units (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Detailed Information About Share Of Profit After Tax Of Equity Accounted Units [Abstract]
Summary of share of profit after tax of equity accounted units	2018 2017 2016 US$m US$m US$m Sales revenue: Rio Tinto share (a) 2,497 1,960 1,727 Operating costs (1,656 ) (1,400 ) (1,237 ) Profit before finance items and taxation 841 560 490 Finance items (69 ) (47 ) (33 ) Share of profit after tax of equity accounted units 14 17 20 Profit before taxation 786 530 477 Taxation (273 ) (191 ) (156 ) Profit for the year (Rio Tinto share) 513 339 321 (a) Sales revenue of equity accounted units includes sales by equity accounted units to Group subsidiaries.

Finance income and finance co_2

Finance income and finance costs (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Finance Income Expense Explanatory [Abstract]
Summary of Finance Income and Finance Cost	2018 2017 2016 Note US$m US$m US$m Finance income from equity accounted units (Rio Tinto share) 7 4 6 Other finance income (including bank deposits and other financial assets) 242 137 83 Total finance income 249 141 89 Interest on: – Financial liabilities at amortised cost and associated derivatives (775 ) (819 ) (895 ) – Finance leases (2 ) (3 ) (3 ) Fair value movements: – Bonds designated as hedged items in fair value hedges 96 28 89 – Derivatives designated as hedging instruments in fair value hedges (73 ) (22 ) (89 ) Loss on early redemption of bonds (a) (94 ) (256 ) (324 ) Amounts capitalised 14 296 224 111 Total finance costs (552 ) (848 ) (1,111 ) (a) In 2018, loss on early redemption of bonds includes a premium charge of US$72 million; unamortised debt issuance costs and fees of US$9 million, the write-off of the fair value hedge adjustment of US$16 million and the reclassification of a gain out of the cost of hedging reserve of US$3 million (see note 30). In 2017, loss on early redemption of bonds included a premium charge of US$238 million; unamortised debt issuance costs and fees of US$14 million and the write-off of the fair value hedge adjustment of US$4 million (see note 30). In 2016, loss of early redemption of bonds included a premium charge of US$441 million; unamortised debt issuance costs and fees of US$42 million partially offset by the write-off of fair value hedge adjustments of US$159 million (see note 30).

Taxation (Tables)

Taxation (Tables)	12 Months Ended
	Dec. 31, 2018
Major Components Of Tax Expense Income [Abstract]
Summary of taxation charge	2018 2017 2016 Note US$m US$m US$m Taxation charge – Current 3,726 3,270 2,115 – Deferred 17 516 695 (548 ) Total taxation charge 4,242 3,965 1,567
Summary of prima facie tax reconciliation	2018 2017 2016 Prima facie tax reconciliation US$m US$m US$m Profit before taxation 18,167 12,816 6,343 Deduct: share of profit after tax of equity accounted units (513 ) (339 ) (321 ) Parent companies' and subsidiaries' profit before tax 17,654 12,477 6,022 Prima facie tax payable at UK rate of 19% (2017: 19%; 2016: 20%) 3,354 2,371 1,204 Higher rate of taxation on Australian underlying earnings 1,106 1,069 604 Impact of items excluded in arriving at underlying earnings (a) – Impairment charges - 10 (16 ) – Net gains and losses on consolidation and disposal of interests in businesses (251 ) (123 ) 30 – Exchange and gains/(losses) on derivatives 32 (48 ) (33 ) – Losses from increases to closure estimates (non-operating and fully impaired sites) 30 - (40 ) – Gain relating to surplus land at Kitimat (81 ) - - – Changes in corporate tax rates in the US and France (b) - 439 - – Onerous port and rail contracts - - (46 ) – Tax provision (c) - - 380 – Tax charge relating to expected divestments (d) - 202 - – Other exclusions - 14 (48 ) Impact of changes in tax rates and laws 47 21 (9 ) Other tax rates applicable outside the UK and Australia on underlying earnings (47 ) (92 ) (283 ) Resource depletion and other depreciation allowances (46 ) (33 ) (15 ) Recognition of previously unrecognised deferred tax assets - (40 ) (154 ) Write-down of previously recognised deferred tax assets (e) 13 160 - Other items (f) 85 15 (7 ) Total taxation charge (g) 4,242 3,965 1,567 (a) The impact for each item includes the effect of tax rates applicable outside the UK. (b) In 2017, deferred tax assets were remeasured to reflect lower corporate income tax rates in the US and France as a result of tax legislation changes substantively enacted in December 2017. (c) Tax provision includes amounts provided for specific tax matters for which the timing of resolution and potential economic outflow are uncertain. During 2016, provision was made in relation to matters under discussion with the Australian Taxation Office (ATO) in relation to the transfer pricing of certain transactions between Rio Tinto entities based in Australia and the Group’s commercial centre in Singapore for the period since 2009. (d) In 2017, deferred tax assets were derecognised as a result of revised profit forecasts in France due to expected divestments of Dunkerque and ISAL. The Dunkerque divestment completed in 2018. (e) The write-down of previously recognised deferred tax assets in 2017 primarily relates to a reduction in recognised deferred tax assets on brought forward losses in Grasberg. (f) Other items include various adjustments to provisions for taxation of prior periods. (g) This tax reconciliation relates to the Group’s parent companies, subsidiaries and joint operations. The Group’s share of profit of equity accounted units is net of tax charges of US$273 million (2017: US$191 million; 2016: US$156 million).
Summary of tax relating to components of other comprehensive income or loss	2018 2017 2016 Total Total Total US$m US$m US$m Tax on fair value movements: – Cash flow hedge fair value (gains)/losses (54 ) (1 ) 4 Tax (charge)/credit on actuarial gains and losses on post-retirement benefit plans (271 ) (12 ) 29 Adjustments to deferred tax on post-retirement benefit plans due to changes in corporate tax rates in the US and France - (140 ) - Tax relating to components of other comprehensive income/(loss) for the year (a) (325 ) (153 ) 33 (a) This comprises a deferred tax charge of US$325 million (2017: charge of US$153 million; 2016: credit of US$33 million) and a current tax charge of US$nil (2017: US$nil; 2016: US$nil), plus a share of tax on other comprehensive income of equity accounted units shown separately (see note 17).

Earnings per ordinary share (Ta

Earnings per ordinary share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Summary of earnings (loss) per ordinary shares	2018 2017 Weighted Weighted average 2018 average 2017 2018 number of Per share 2017 number of Per share Earnings shares amount Earnings shares amount US$m (millions) (cents) US$m (millions) (cents) Basic earnings per share attributable to ordinary shareholders of Rio Tinto (a) 13,638 1,719.3 793.2 8,762 1,786.7 490.4 Diluted earnings per share attributable to ordinary shareholders of Rio Tinto (b) 13,638 1,731.7 787.6 8,762 1,799.5 486.9 2016 Weighted average 2016 2016 number of Per share Earnings shares amount US$m (millions) (cents) Basic earnings per share attributable to ordinary shareholders of Rio Tinto (a) 4,617 1,797.3 256.9 Diluted earnings per share attributable to ordinary shareholders of Rio Tinto (b) 4,617 1,808.6 255.3 (a) The weighted average number of shares is calculated as the average number of Rio Tinto plc shares outstanding not held as treasury shares of 1,312.7 million (2017: 1,364.5 million; 2016: 1,373.7 million) plus the average number of Rio Tinto Limited shares outstanding of 406.6 million (2017: 422.3 million; 2016: 423.6 million) over the relevant period. No Rio Tinto Limited ordinary shares were held by Rio Tinto plc in any of the periods presented. (b) For the purposes of calculating diluted earnings per share, the effect of dilutive securities of 12.4 million shares in 2018 (2017: 12.8 million; 2016: 11.3 million) is added to the weighted average number of shares described in (a) above. This effect is calculated under the treasury stock method. In accordance with IAS 33 “Earnings per share”. The Group’s only potential dilutive ordinary shares are share options for which terms and conditions are described in note 43.

Dividends (Tables)

Dividends (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Dividends [Abstract]
Summary of dividends paid	2018 2017 2016 US$m US$m US$m Rio Tinto plc previous year final dividend paid 2,446 1,725 1,443 Rio Tinto plc interim dividend paid 1,666 1,530 604 Rio Tinto Limited previous year final dividend paid 731 523 473 Rio Tinto Limited interim dividend paid 513 472 205 Dividends paid during the year 5,356 4,250 2,725 Dividends per share: paid during the year 307.0 c 235.0 c 152.5 c Final dividends per share: proposed in the announcement of the results for the year 180.0c 180.0 c 125.0 c Special dividends per share: proposed in the announcement of the results for the year 243.0c - -
Summary of dividends per share	Dividends Dividends Dividends per share per share per share 2018 2017 2016 Rio Tinto plc previous year final (pence) 129.43 p 100.56 p 74.21 p Rio Tinto plc interim (pence) 96.82 p 83.13 p 33.80 p Rio Tinto Limited previous year final – fully franked at 30% (Australian cents) 228.53 c 163.62 c 151.89 c Rio Tinto Limited interim – fully franked at 30% (Australian cents) 170.84 c 137.72 c 59.13 c
Summary of number of shares dividend distributed	Number Number Number of shares of shares of shares 2018 2017 2016 (millions) (millions) (millions) Rio Tinto plc previous year final 1,334.8 1,374.6 1,373.9 Rio Tinto plc interim 1,308.4 1,366.1 1,374.4 Rio Tinto Limited previous year final 412.4 424.0 423.5 Rio Tinto Limited interim 412.4 424.0 424.0

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill [Abstract]
Summary of goodwill	2018 2017 US$m US$m Net book value At 1 January 1,037 951 Adjustment on currency translation (125 ) 86 At 31 December 912 1,037 – cost 15,861 17,942 – accumulated impairment (14,949 ) (16,905 ) At 1 January – cost 17,942 17,144 – accumulated impairment (16,905 ) (16,193 ) At 31 December, goodwill has been allocated as follows: 2018 2017 US$m US$m Net book value Richards Bay Minerals 474 552 Pilbara 351 389 Dampier Salt 87 96 912 1,037
Key assumptions calculation of fair value less costs of disposal	The key assumptions to which the calculation of FVLCD for Richards Bay Minerals is most sensitive and the corresponding decrease in FVLCD are set out below: US$m 5% decrease in the titanium slag price 174 1% increase in the discount rate applied to post-tax cash flows 195 10% strengthening of the South African rand 328

Intangible assets (Tables)

Intangible assets (Tables)	12 Months Ended
	Dec. 31, 2018
Intangible Assets [Abstract]
Summary of intangible assets	Trademarks, Contract- Exploration patented and based Other and non-patented intangible intangible evaluation (a) technology assets (b) assets Total Year ended 31 December 2018 US$m US$m US$m US$m US$m Net book value At 1 January 2018 393 75 2,188 463 3,119 Adjustment on currency translation (25 ) (3 ) (171 ) (46 ) (245 ) Expenditure during the year 90 1 - 83 174 Amortisation for the year (c) - (14 ) (23 ) (96 ) (133 ) Impairment charges (d) - - - (2 ) (2 ) Disposals, transfers and other movements (e) (225 ) - (12 ) 103 (134 ) At 31 December 2018 233 59 1,982 505 2,779 – cost 2,346 217 3,114 1,538 7,215 – accumulated amortisation and impairment (2,113 ) (158 ) (1,132 ) (1,033 ) (4,436 ) Trademarks, Contract- Exploration patented and based Other and non-patented intangible intangible evaluation (a) technology assets (b) assets Total Year ended 31 December 2017 US$m US$m US$m US$m US$m Net book value At 1 January 2017 711 78 2,103 387 3,279 Adjustment on currency translation 27 10 150 29 216 Expenditure during the year 57 - - 65 122 Amortisation for the year (c) - (13 ) (67 ) (97 ) (177 ) Impairment charges (d) (357 ) - - - (357 ) Disposals, transfers and other movements (e) (45 ) - 2 79 36 At 31 December 2017 393 75 2,188 463 3,119 – cost 2,658 224 3,438 1,537 7,857 – accumulated amortisation and impairment (2,265 ) (149 ) (1,250 ) (1,074 ) (4,738 ) (a) Exploration and evaluation assets’ useful lives are not determined until transferred to property, plant and equipment. (b) The Group benefits from certain intangible assets acquired with Alcan, including power supply contracts, customer contracts and water rights. The water rights are expected to contribute to the efficiency and cost-effectiveness of operations for the foreseeable future: accordingly, these rights are considered to have indefinite lives and are not subject to amortisation but are tested annually for impairment. These water rights constitute the majority of the amounts in “Contract-based intangible assets”. The remaining carrying value of the water rights (US$1,684 million) as at 31 December 2018 relates wholly to the Quebec smelters CGU. The Quebec smelters CGU was tested for impairment by reference to FVLCD using discounted cash flows, which is in line with the policy set out in note 1(i). The recoverable amount of the Quebec smelters is classified as level 3 under the fair value hierarchy. In arriving at FVLCD, post-tax cash flows expressed in real terms have been estimated over the expected useful economic lives of the underlying smelting assets and discounted using a real post-tax discount rate of 6.8% (2017: 6.7%). The recoverable amounts were determined to be significantly in excess of carrying value, and there are no reasonably possible changes in key assumptions that would cause the remaining water rights to be impaired. (c) Finite life intangible assets are amortised over their useful economic lives on a straight line or units of production basis, as appropriate. Where amortisation is calculated on a straight line basis, the following useful lives have been determined: Trademarks, patented and non-patented technology Trademarks: 14 to 20 years Patented and non-patented technology: ten to 20 years Contract-based intangible assets Power contracts/water rights: two to 45 years Other purchase and customer contracts: five to 15 years Other intangible assets Internally generated intangible assets and computer software: two to five years Other intangible assets: two to 20 years (d) Impairment charges in 2018 relate to the ISAL Smelter (see note 6). Impairment charges in 2017 relate to the full write-off of the Roughrider deposit in Canada (see note 6). (e) Disposals, transfers and other movements includes transfers to assets held for sale relating to Rössing Uranium and ISAL assets, transfers to Mining properties and leases in relation to the Koodaideri mine from Exploration and evaluation, offset by transfers into other intangibles as part of the Autohaul project. Disposals, transfers and other movements for Exploration and evaluation in 2017 included US$34 million transferred to Mining Property in relation to the Kemano tunnel following approval of the project.
Summary of exploration and evaluation expenditure	The charge for the year and the net amount of intangible assets capitalised during the year are as follows: 2018 2017 2016 US$m US$m US$m Net expenditure in the year (net of cash proceeds of US$233 million (2017: US$3 million; 2016: US$208 million) on disposal of undeveloped projects) (345 ) (493 ) (284 ) Non-cash movements and non-cash proceeds on disposal of undeveloped projects 45 (24 ) (177 ) Amount capitalised during the year 90 57 8 Net charge for the year (210 ) (460 ) (453 ) Reconciliation to income statement Exploration and evaluation costs (488 ) (445 ) (497 ) Profit/(loss) relating to interests in undeveloped projects (a) 278 (15 ) 44 Net charge for the year (210 ) (460 ) (453 ) (a) During 2018, profit relating to interests in undeveloped properties relates to the gains on the sales of Valeria (US$83 million) and Winchester South (US$195 million) undeveloped properties which are included within underlying earnings.

Property, plant and equipment (

Property, plant and equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Summary of property, plant and equipment	Mining Land Plant Capital properties and and works in and leases (a) buildings (b) equipment progress Total Year ended 31 December 2018 Note US$m US$m US$m US$m US$m Net book value At 1 January 2018 11,488 7,376 36,285 6,944 62,093 Adjustment on currency translation (c) (689 ) (548 ) (2,671 ) (249 ) (4,157 ) Adjustments to capitalised closure costs 26 486 - - - 486 Interest capitalised (d) 8 - - - 296 296 Additions 403 80 459 4,359 5,301 Depreciation for the year (a) (e) (664 ) (382 ) (2,836 ) - (3,882 ) Impairment charges (f) (3 ) (20 ) (101 ) (6 ) (130 ) Disposals (1 ) (54 ) (71 ) (4 ) (130 ) Subsidiaries no longer consolidated (g) (1,103 ) (377 ) (1,392 ) (514 ) (3,386 ) Transfers and other movements (h) 1,146 188 2,346 (3,810 ) (130 ) At 31 December 2018 11,063 6,263 32,019 7,016 56,361 – cost 23,318 10,601 63,051 7,324 104,294 – accumulated depreciation and impairment (12,255 ) (4,338 ) (31,032 ) (308 ) (47,933 ) Non-current assets held under finance leases (i) - - 31 - 31 Non-current assets pledged as security (j) 3,054 385 5,194 4,588 13,221 Mining Land Plant Capital properties and and works in and leases (a) buildings (b) equipment progress Total Year ended 31 December 2017 Note US$m US$m US$m US$m US$m Net book value At 1 January 2017 10,848 7,316 35,706 4,985 58,855 Adjustment on currency translation (c) 495 461 2,242 183 3,381 Adjustments to capitalised closure costs 26 710 - - - 710 Interest capitalised (d) 8 - - - 224 224 Additions 230 41 646 3,834 4,751 Depreciation for the year (a) (e) (673 ) (403 ) (3,122 ) - (4,198 ) Impairment charges (f) (304 ) (2 ) (128 ) (1 ) (435 ) Disposals - (57 ) (40 ) (26 ) (123 ) Subsidiaries no longer consolidated (g) (211 ) (95 ) (417 ) (26 ) (749 ) Transfers and other movements (h) 393 115 1,398 (2,229 ) (323 ) At 31 December 2017 11,488 7,376 36,285 6,944 62,093 – cost 24,691 12,029 71,903 7,266 115,889 – accumulated depreciation and impairment (13,203 ) (4,653 ) (35,618 ) (322 ) (53,796 ) Non-current assets held under finance leases (i) - - 37 - 37 Non-current assets pledged as security (j) 3,307 410 5,308 3,278 12,303 (a) At 31 December 2018, the net book value of capitalised production phase stripping costs totalled US$2,050 million, with US$1,572 million within Property, plant and equipment and a further US$478 million within Investments in equity accounted units (2017: total of US$1,815 million with US$1,374 million in Property, plant and equipment and a further US$441 million within Investments in equity accounted units). During the year capitalisation of US$526 million was partly offset by depreciation of US$274 million (including amounts recorded within equity accounted units). Depreciation of deferred stripping costs in respect of subsidiaries of US$134 million (2017: US$194 million; 2016: US$203 million) is included within “Depreciation for the year”. (b) At 31 December 2018, the net book value amount for land and buildings includes freehold US$6,240 million (2017: US$7,294 million) and long leasehold US$23 million (2017: US$82 million). (c) Adjustment on currency translation represents the impact of exchange differences arising on the translation of the assets of entities with functional currencies other than the US dollar, recognised directly in the currency translation reserve. The adjustment in 2018 arose from the strengthening of the US dollar against other currencies. (d) Interest is capitalised at a rate based on the Group or relevant subsidiary’s cost of borrowing or at the rate on project specific debt, where applicable. The Group’s average borrowing rate used for capitalisation of interest is 4.90% (2017: 4.45%). (e) Assets within operations for which production is not expected to fluctuate significantly from one year to another or which have a physical life shorter than the related mine are depreciated on a straight line basis as follows: Land and buildings Land: not depreciated Buildings: five to 50 years Plant and equipment Other plant and equipment: three to 50 years Power assets: 25 to 50 years Capital work in progress: not depreciated (f) During 2018, impairment charges primarily related to the ISAL Smelter (see note 6). During 2017, impairment charges primarily related to Argyle Diamonds and Rössing Uranium (see note 6). (g) During 2018, “Subsidiaries no longer consolidated” relates primarily to the disposal of Kestrel and Hail Creek, which completed on 1 August 2018 and the disposal of Grasberg on 21 December 2018. Refer to note 37. During 2017, “Subsidiaries no longer consolidated” relates primarily to the disposal of Coal & Allied Industries Limited, which completed on 1 September 2017. (h) “Transfers and other movements” includes reclassifications between categories and transfers to assets held for sale relating to Rössing Uranium and ISAL assets in 2018, and Dunkerque in 2017. (i) The finance leases under which these assets are held are disclosed in note 23. (j) Excludes assets held under finance leases. Non-current assets pledged as security represent amounts pledged as collateral against US$4,562 million (2017: US$4,677 million) of loans, which are included in note 22.

Investments in equity account_2

Investments in equity accounted units (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Investments Accounted For Using Equity Method Explanatory [Abstract]
Summary of investments in equity accounted units	2018 2017 Summary balance sheet (Rio Tinto share) US$m US$m Rio Tinto's share of assets – Non-current assets 6,000 5,913 – Current assets 887 990 6,887 6,903 Rio Tinto's share of liabilities – Current liabilities (607 ) (654 ) – Non-current liabilities (1,981 ) (1,763 ) (2,588 ) (2,417 ) Rio Tinto's share of net assets 4,299 4,486

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Inventories [Abstract]
Summary of inventories	2018 2017 US$m US$m Raw materials and purchased components 734 648 Consumable stores 862 875 Work in progress 1,026 1,082 Finished goods and goods for resale 977 1,027 Total inventories 3,599 3,632 Comprising: Expected to be used within one year 3,447 3,472 Expected to be used after more than one year 152 160 Total inventories 3,599 3,632

Deferred taxation (Tables)

Deferred taxation (Tables)	12 Months Ended
	Dec. 31, 2018
Deferred Tax Assets And Liabilities [Abstract]
Reconciliation of changes in deferred tax liability asset	2018 2017 US$m US$m At 1 January – 233 (607 ) Adjustment to opening balance on transition to IFRS 15 (71 ) - At 1 January – restated opening balance 162 (607 ) Adjustment on currency translation (172 ) 53 Charged to the income statement 516 695 Charged to statement of comprehensive income (a) 325 153 Disposals (263 ) - Other movements (b) (32 ) (61 ) At 31 December – 536 233 Comprising: – deferred tax liabilities (c) (d) 3,673 3,628 – deferred tax assets (c) (e) (f) (3,137 ) (3,395 )
Deferred tax liabilities and assets, prior to offsetting of balances	The closing deferred tax liabilities and assets, prior to this offsetting of balances, are shown below. Total Total 2018 2017 US$m US$m Deferred tax liabilities arising from: Capital allowances 4,408 5,208 Unremitted earnings (d) 454 588 Capitalised interest 259 391 Unrealised exchange gains 5 31 Other temporary differences 309 222 Total 5,435 6,440 Deferred tax assets arising from: Tax losses (e) (1,894 ) (2,282 ) Provisions (1,585 ) (1,731 ) Capital allowances (154 ) (579 ) Post-retirement benefits (293 ) (616 ) Unrealised exchange losses (187 ) (317 ) Other temporary differences (786 ) (682 ) Total (4,899 ) (6,207 ) Charged/(credited) to the income statement Unrealised exchange losses 57 36 Tax losses (30 ) 12 Provisions (19 ) 451 Capital allowances 461 278 Tax on unremitted earnings (33 ) 4 Post-retirement benefits 30 149 Other temporary differences 50 (235 ) Total 516 695 (a) The amounts charged directly to the Statement of comprehensive income include provisions for tax on exchange differences on intragroup loans qualifying for reporting as part of the net investment in subsidiaries, on cash flow hedges and on actuarial gains and losses on pension schemes and on post-retirement healthcare plans. (b) “Other movements” include deferred tax relating to tax payable recognised by subsidiary holding companies on the profits of the equity accounted units to which it relates. (c) The deferred tax liability of US$3,673 million (2017: US$3,628 million) includes US$3,658 million (2017: US$3,615 million) due in more than one year. The deferred tax asset of US$3,137 million (2017: US$3,395 million) includes US$3,133 million (2017: US$3,386 million) receivable in more than one year. All amounts are shown as non-current on the face of the balance sheet as required by IAS 12. (d) Deferred tax is not recognised on the unremitted earnings of subsidiaries and joint ventures totalling US$3,726 million (2017: US$3,242 million) where the Group is able to control the timing of the remittance and it is probable that there will be no remittance in the foreseeable future. If these earnings were remitted, tax of US$157 million (2017: US$131 million) would be payable. (e) There is a limited time period, the shortest of which is six years, for the recovery of US$1,519 million (2017: US$1,679 million) of tax losses and other tax assets which have been recognised as deferred tax assets in the financial statements. (f) Recognised and unrecognised deferred tax assets are shown in the table below and totalled US$5,647 million at 31 December 2018 (2017: US$7,071 million). Of this total, US$3,137 million has been recognised as deferred tax assets (2017: US$3,395 million), leaving US$2,510 million (2017: US$3,676 million) unrecognised, as recovery is not considered probable.
Recognised and unrecognised amounts in deferred tax assets	The recognised amounts do not include deferred tax assets that have been netted off against deferred tax liabilities. Recognised Unrecognised 2018 2017 2018 2017 At 31 December US$m US$m US$m US$m France - - 1,122 1,163 Canada 545 546 559 674 US 932 877 12 7 Australia 796 1,055 289 257 Mongolia (a) 703 631 87 61 Other (b) 161 286 441 1,514 Total 3,137 3,395 2,510 3,676 (a) Deferred tax assets in Mongolia include US$469 million (2017: US$432 million) from tax losses that expire if not recovered against taxable profits within eight years. Tax losses have been calculated in accordance with the provisions of the Oyu Tolgoi Investment Agreement and Mongolian laws. Recovery of the recognised deferred tax assets is expected to commence from 2024 based on projected cash flows in the latest life-of-mine plan, which has been calculated on a consistent basis with the impairment test described in note 6. Tax law in Mongolia and its interpretation by the tax authority has been, and is expected to continue to be, subject to change. Such future changes could have a material impact on the amount and period of recovery of these deferred tax assets. (b) US$684 million (2017: US$777 million) of the unrecognised assets relate to realised or unrealised capital losses, the recovery of which depends on the existence of capital gains in future years. There is a time limit, the shortest of which is one year, for the recovery of US$96 million of the unrecognised assets (2017: US$250 million).

Trade and other receivables (Ta

Trade and other receivables (Tables)	12 Months Ended
	Dec. 31, 2018
Trade And Other Receivables [Abstract]
Summary of trade and other receivables	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 US$m US$m US$m US$m US$m US$m Trade receivables (a) - 2,167 2,167 1 2,314 2,315 Other financial receivables (a) 240 550 790 178 462 640 Amounts due from equity accounted units - 50 50 - 30 30 Other receivables 129 226 355 348 358 706 Prepayment of tolling charges to jointly controlled entities (b) 228 - 228 269 - 269 Pension surpluses (note 44) 935 - 935 871 - 871 Other prepayments 53 186 239 57 279 336 Total 1,585 3,179 4,764 1,724 3,443 5,167 (a) At 31 December 2018, trade and other financial receivables are stated net of allowances for expected credit losses of US$8 million. The 2017 closing provision for doubtful debt under IAS 39 of US$55 million was adjusted by US$7 million (pre-tax) upon adoption of IFRS 9 (refer to note 45). During the year there has been an increase to the provision for expected credit losses of US$2 million and US$42 million has been utilised. (b) These prepayments will be charged to Group operating costs as processing takes place.

Assets and liabilities held f_2

Assets and liabilities held for sale (Tables)	12 Months Ended
	Dec. 31, 2018
Noncurrent Assets Or Disposal Groups Classified As Held For Sale Or As Held For Distribution To Owners [Abstract]
Summary of major classes of assets and liabilities classified as held for sale	The major classes of assets and liabilities of those entities classified as held for sale at 31 December 2018 are: 2018 2017 US$m US$m Assets Intangible assets 4 6 Property, plant and equipment 238 190 Investments in equity accounted units 5 - Inventories 186 88 Deferred tax assets 66 49 Trade and other receivables 58 139 Other financial assets (including loans to equity accounted units) 60 22 Cash and cash equivalents 117 - Assets of disposal groups held for sale 734 494 Liabilities Trade and other payables (134) (60) Provisions including post-retirement benefits (160) (64) Liabilities of disposal groups held for sale (294) (124) Net assets associated with disposal groups 440 370

Other financial assets (inclu_2

Other financial assets (including non-quasi equity loans to equity accounted units) (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Other Financial Assets [Abstract]
Summary of other financial assets including non-quasi equity loans to equity accounted units	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 US$m US$m US$m US$m US$m US$m Derivative financial instruments 468 88 556 238 29 267 Equity shares and quoted funds 53 77 130 45 91 136 Other investments, including loans (a) 255 2,527 2,782 188 964 1,152 Loans to equity accounted units 38 - 38 39 - 39 Total 814 2,692 3,506 510 1,084 1,594 (a) Current “Other investments, including loans” comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets held in managed investment funds classified as held for trading.

Cash and cash equivalents (Tabl

Cash and cash equivalents (Tables)	12 Months Ended
	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
Summary of cash and cash equivalents	2018 2017 Note US$m US$m Cash at bank and in hand 740 1,035 Money market funds and other cash equivalents 10,033 9,515 Balance per Group balance sheet 10,773 10,550 Bank overdrafts repayable on demand (unsecured) 22 (1 ) (3 ) Cash and cash equivalents included in Assets held for sale 19 117 - Balance per Group cash flow statement 10,889 10,547

Borrowings and other financia_2

Borrowings and other financial liabilities (Tables)	12 Months Ended
	Dec. 31, 2018
Borrowings And Other Financial Liabilities [Abstract]
Summary of borrowings	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 Borrowings at 31 December Note US$m US$m US$m US$m US$m US$m Rio Tinto Finance plc Euro Bonds 2.0% due 2020 (a) (b) 468 - 468 921 - 921 Rio Tinto Finance (USA) Limited Bonds 4.125% 2021 (a) - - - 428 - 428 Rio Tinto Finance (USA) Limited Bonds 3.750% 2021 (a) - - - 347 - 347 Rio Tinto Finance (USA) plc Bonds 3.5% 2022 (a) - - - 227 - 227 Rio Tinto Finance (USA) plc Bonds 2.875% 2022 (a) - - - 377 - 377 Rio Tinto Finance plc Euro Bonds 2.875% due 2024 (a) (b) 514 - 514 644 - 644 Rio Tinto Finance (USA) Limited Bonds 3.75% 2025 (a) 1,170 - 1,170 1,192 - 1,192 Rio Tinto Finance (USA) Limited Bonds 7.125% 2028 (a) 927 - 927 965 - 965 Alcan Inc. Debentures 7.25% due 2028 104 - 104 105 - 105 Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 (a) (b) 633 - 633 669 - 669 Alcan Inc. Debentures 7.25% due 2031 421 - 421 422 - 422 Alcan Inc. Global Notes 6.125% due 2033 741 - 741 740 - 740 Alcan Inc. Global Notes 5.75% due 2035 288 - 288 287 - 287 Rio Tinto Finance (USA) Limited Bonds 5.2% 2040 (a) 1,095 - 1,095 1,102 - 1,102 Rio Tinto Finance (USA) plc Bonds 4.75% 2042 (a) 462 - 462 467 - 467 Rio Tinto Finance (USA) plc Bonds 4.125% 2042 (a) 685 - 685 691 - 691 Oyu Tolgoi LLC MIGA Insured Loan LIBOR plus 2.65% due 2027 (c) 676 - 676 674 - 674 Oyu Tolgoi LLC Commercial Banks "B Loan" LIBOR plus 3.4% due 2027 (c) 1,588 - 1,588 1,588 - 1,588 Oyu Tolgoi LLC Export Credit Agencies Loan 2.3% due 2028 (c) 272 - 272 255 - 255 Oyu Tolgoi LLC Export Credit Agencies Loan LIBOR plus 3.65% due 2029 (c) 871 - 871 869 - 869 Oyu Tolgoi LLC International Financial Institutions "A Loan" LIBOR plus 3.78% due 2030 (c) 768 - 768 761 - 761 Loans from equity accounted units - - - - 31 31 Other secured loans 345 42 387 451 79 530 Other unsecured loans 373 264 637 393 435 828 Finance leases 23 39 5 44 49 4 53 Bank overdrafts 21 - 1 1 - 3 3 Total borrowings including overdrafts (d) 12,440 312 12,752 14,624 552 15,176 (a) These borrowings are subject to the hedging arrangements summarised below. Fair value hedge accounting has been applied except for the Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 which has cash flow hedge accounting applied. (b) Rio Tinto has a US$10 billion (2017: US$10 billion) European Debt Issuance Programme against which the cumulative amount utilised was US$1.6 billion equivalent at 31 December 2018 (2017: US$2.2 billion). The carrying value of these bonds after hedge accounting adjustments amounted to US$1.6 billion (2017: US$ 2.2 billion) in aggregate. (c) These borrowings relate to the Oyu Tolgoi LLC project finance facility. The project finance facility provides for interest-only payments for the first five years followed by minimum repayments according to a stepped amortisation schedule for the remaining life of the facility. The due dates stated represent the final repayment date. The interest rates stated are pre-completion and will increase by 1% post-completion. (d) The Group’s borrowings of US$12.8 billion (2017: US$15.2 billion) include US$2.4 billion (2017: US$2.7 billion) which relates to subsidiary entity borrowings that are without recourse to the Group, and US$4.6 billion (2017: US$4.7 billion) which is subject to various financial and general covenants with which the respective borrowers were in compliance as at 31 December 2018.
Summary of borrowings and other financial liabilities	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 Other financial liabilities US$m US$m US$m US$m US$m US$m Derivative financial instruments 407 95 502 481 50 531 Other financial liabilities - 666 666 43 302 345 Total other financial liabilities 407 761 1,168 524 352 876 Total borrowings including overdrafts (as above) 12,440 312 12,752 14,624 552 15,176 Total borrowings and other financial liabilities 12,847 1,073 13,920 15,148 904 16,052

Capitalised finance leases (Tab

Capitalised finance leases (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Capitalised Finance Leases [Abstract]
Summary of capitalised finance leases	2018 2017 Note US$m US$m Present value of minimum lease payments Total minimum lease payments 45 57 Effect of discounting (1 ) (4 ) Total 22 44 53 Payments under capitalised finance leases Due within 1 year 5 4 Between 1 and 3 years 10 14 Between 3 and 5 years 18 28 More than 5 years 12 11 Total 45 57

Consolidated net cash_(debt) (T

Consolidated net cash/(debt) (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Consolidated Net Debt [Abstract]
Analysis of changes in consolidated net cash/(debt)	Financing liabilities (b) Other assets Borrowings (including finance leases) excluding Debt-related derivatives (included in Other financial assets/ Cash/ Other Net overdrafts (a) liabilities) overdrafts (b) investments (c) (debt)/cash Year ended 31 December 2018 US$m US$m US$m US$m US$m Analysis of changes in consolidated net cash/(debt) Opening balance (15,173 ) (177 ) 10,547 958 (3,845 ) Foreign exchange adjustment 126 (64 ) 151 - 213 Cash movements excluding exchange movements 2,246 51 191 1,557 4,045 Other non-cash movements 50 (98 ) (117 ) 7 (158 ) Closing balance (12,751 ) (288 ) 10,772 2,522 255 Financing liabilities (b) Other assets Borrowings (including finance leases) excluding Debt-related derivatives (included in Other financial assets/ Cash/ Other Net overdrafts (a) liabilities) overdrafts (b) investments (c) debt Year ended 31 December 2017 US$m US$m US$m US$m US$m Analysis of changes in consolidated net debt Opening balance (17,618 ) (408 ) 8,189 250 (9,587 ) Foreign exchange adjustment (303 ) 245 (12 ) - (70 ) Cash movements excluding exchange movements 2,777 7 2,370 705 5,859 Other non-cash movements (29 ) (21 ) - 3 (47 ) Closing balance (15,173 ) (177 ) 10,547 958 (3,845 ) (a) Borrowings (including finance leases) at 31 December 2018 differ from total borrowings on the balance sheet as they exclude overdrafts of US$1 million (31 December 2017: US$3 million), other current financial liabilities of US$761 million (31 December 2017: US$352 million) and other non-current financial liabilities US$407 million (31 December 2017: US$524 million). (b) Closing cash/overdrafts at 31 December 2018 differ from cash and cash equivalents on the balance sheet as they include overdrafts of US$1 million which have been classified as a financial liability (31 December 2017: US$3 million). Other non-cash movements represents the reclassification of cash and cash equivalents in disposal groups to assets held for sale. (c) Other investments comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets held in managed investment funds classified as held for trading.

Trade and other payables (Table

Trade and other payables (Tables)	12 Months Ended
	Dec. 31, 2018
Trade And Other Payables [Abstract]
Summary of trade and other payables	Non-current Current Total Non-current Current Total 2018 2018 2018 2017 2017 2017 US$m US$m US$m US$m US$m US$m Trade payables - 3,180 3,180 - 3,255 3,255 Other financial payables 256 653 909 265 867 1,132 Other payables 165 114 279 87 97 184 Deferred income (a) 176 234 410 246 246 492 Accruals 11 1,229 1,240 13 1,347 1,360 Employee entitlements - 630 630 - 734 734 Royalties and mining taxes 1 487 488 4 492 496 Amounts owed to equity accounted units 156 67 223 156 19 175 Government grants deferred 76 6 82 85 4 89 Total 841 6,600 7,441 856 7,061 7,917 (a) Deferred income includes contract liabilities of US$198 million.

Provisions (including post-re_2

Provisions (including post-retirement benefits) (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Other Provisions [Abstract]
Summary of Provisions including post-retirement benefits	Pensions Close-down and Other and post-retirement employee restoration/ Total Total healthcare (a) entitlements (b) environmental (c) Other 2018 2017 Note US$m US$m US$m US$m US$m US$m At 1 January 3,370 389 9,983 900 14,642 13,794 Adjustment on currency translation (145 ) (37 ) (656 ) (60 ) (898 ) 846 Adjustments to mining properties: 14 – changes in estimate - - 486 - 486 710 Charged/(credited) to profit: – increases to existing and new provisions 267 185 456 229 1,137 797 – unused amounts reversed - (36 ) (38 ) (70 ) (144 ) (187 ) – exchange losses/(gains) on provisions - - 13 3 16 (83 ) – amortisation of discount - - 372 9 381 383 Utilised in year (219 ) (122 ) (319 ) (177 ) (837 ) (1,053 ) Actuarial (gains)/losses recognised in equity (781 ) - - - (781 ) 121 Subsidiaries no longer consolidated (d) - (29 ) (257 ) (32 ) (318 ) (622 ) Transfers and other movements (e) (6 ) 10 (65 ) (15 ) (76 ) (64 ) At 31 December 2,486 360 9,975 787 13,608 14,642 Balance sheet analysis: Current 79 274 476 227 1,056 1,275 Non-current 2,407 86 9,499 560 12,552 13,367 Total 2,486 360 9,975 787 13,608 14,642 (a) The main assumptions used to determine the provision for pensions and post-retirement healthcare, and other information, including the expected level of future funding payments in respect of those arrangements, are given in note 44. (b) The provision for other employee entitlements includes a provision for long service leave of US$242 million (2017: US$292 million), based on the relevant entitlements in certain Group operations and includes US$46 million (2017: US$24 million) of provision for redundancy and severance payments. (c) The Group’s policy on close-down and restoration costs is described in note 1(k) on page 159 and in paragraph (iv) under “Critical accounting policies and estimates” on pages 162 to 164. Close-down and restoration costs are a normal consequence of mining, and the majority of close-down and restoration expenditure is incurred in the years following closure of the mine, refinery or smelter. Remaining lives of operations and infrastructure range from one to over 60 years with an average for all sites, weighted by present closure obligation, of around 17 years (2017: 20 years). Although the ultimate cost to be incurred is uncertain, the Group’s businesses estimate their respective costs based on current restoration standards and techniques. Provisions of US$9,975 million (2017: US$9,983 million) for close-down and restoration costs and environmental clean-up obligations are based on risk-adjusted cash flows. These estimates have been discounted to their present value at a real risk-free rate of 2% per annum, based on an estimate of the long-term, risk-free, pre-tax cost of borrowing. If the risk-free rate was decreased by 0.5% then the provision would be US$1,139 million higher. Non-current provisions for close-down and restoration/environmental expenditure include amounts relating to environmental clean-up of US$535 million (2017: US$336 million) expected to take place between one and five years from the balance sheet date, and US$683 million (2017: US$839 million) expected to take place later than five years after the balance sheet date. Close-down and restoration/environmental liabilities at 31 December 2018 have not been adjusted for amounts of US$110 million (2017: US$75 million) arising from closure-related receivables from the co-owners of the Diavik Joint Venture and insurance recoveries and other financial assets held for the purposes of meeting these obligations. (d) “Subsidiaries no longer consolidated” relates primarily to the disposal of Kestrel and Hail Creek, which completed on 1 August 2018 and the disposal of Grasberg on 21 December 2018. In 2017 it related to the disposal of Coal & Allied Industries Limited, which completed on 1 September 2017. Refer to note 37. (e) Transfers and other movements include transfers to liabilities held for sale relating to Rössing Uranium and ISAL provisions. It also includes an adjustment to record Diavik Diamond Mines Inc. obligations for close-down and restoration on a 100% basis (previously 60% share). Refer to note 33 footnote (e).

Share capital - Rio Tinto plc (

Share capital - Rio Tinto plc (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Classes Of Share Capital [Abstract]
Summary of share capital rio tinto plc	2018 2017 2016 Number Number Number 2018 2017 2016 (million) (million) (million) US$m US$m US$m Issued and fully paid up share capital of 10p each At 1 January 1,351.609 1,384.520 1,384.487 220 224 224 Ordinary shares issued (a) (c) 0.035 0.026 0.033 - - - Shares purchased and cancelled (b) (63.984 ) (32.937 ) - (9 ) (4 ) - At 31 December 1,287.660 1,351.609 1,384.520 211 220 224 Shares held by public At 1 January 1,342.058 1,374.822 1,374.046 Shares reissued from treasury (a) 0.106 0.147 0.743 Shares purchased and cancelled (b) (63.984 ) (32.937 ) - Ordinary shares issued (a) (c) 0.035 0.026 0.033 At 31 December 1,278.215 1,342.058 1,374.822 Shares held in treasury 9.445 9.551 9.698 Shares held by public 1,278.215 1,342.058 1,374.822 Total share capital 1,287.660 1,351.609 1,384.520 Other share classes Special Voting Share of 10p each (d) 1 only 1 only 1 only DLC Dividend Share of 10p each (d) 1 only 1 only 1 only Equalisation Share of 10p each (d) 1 only 1 only 1 only (a) 35,380 ordinary shares were issued in 2018 under the Global Employee Share Plan (GESP). 106,045 ordinary shares were reissued from treasury during the year resulting from the vesting of awards and the exercise of options under Rio Tinto plc employee share-based payment plans, with exercise prices and market values between £16.53 and £43.79 per share (2017: 26,241 ordinary shares were issued under the GESP and 147,126 ordinary shares were reissued from treasury with exercise prices and market values between £28.63 and £37.78 per share; 2016: 33,210 ordinary shares were issued under the GESP and 743,380 ordinary shares reissued from treasury with exercise prices and market values between £16.53 and £32.23 per share). (b) The authority for the company to buy-back its ordinary shares was renewed at the 2018 annual general meeting. 63,984,287 shares were bought back and cancelled in 2018 under the on-market buy-back programme. 32,937,109 shares were bought back and cancelled in 2017 under the on-market buy-back programme. No shares were bought back in 2016. (c) The aggregate consideration for new shares issued under the GESP was US$1.0 million (2017: US$1.0 million; 2016: US$0.9 million). The difference between the nominal value and the issue price of the shares issued was credited to the share premium account. The aggregate consideration received for treasury shares reissued was US (d) The “Special Voting Share” was issued to facilitate the joint voting by shareholders of Rio Tinto plc and Rio Tinto Limited on Joint Decisions, following the DLC Merger. The “DLC Dividend Share” was issued to facilitate the efficient management of funds within the DLC structure. Directors have the ability to issue an Equalisation Share if that is required under the terms of the DLC Merger Sharing Agreement.

Share capital - Rio Tinto Lim_2

Share capital - Rio Tinto Limited (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Classes Of Share Capital [Abstract]
Summary of share capital rio tinto limited	2018 2017 2016 Number Number Number 2018 2017 2016 (million) (million) (million) US$m US$m US$m Issued and fully paid up share capital At 1 January 412.41 424.19 424.19 4,140 3,915 3,950 Adjustment on currency translation (382 ) 310 (35 ) Ordinary shares purchased and cancelled (a) (b) (41.20 ) (11.78 ) - (281 ) (85 ) - At 31 December 371.21 412.41 424.19 3,477 4,140 3,915 – Special Voting Share (c) 1 only 1 only 1 only – DLC Dividend Share (c) 1 only 1 only 1 only Total share capital 371.21 412.41 424.19 (a) In November 2018, 41,198,134 Rio Tinto Limited ordinary shares were purchased at A$69.69 per share and cancelled under an off-market share buy-back programme carried out pursuant to the shareholder approval granted at Rio Tinto Limited’s 2018 annual general meeting for off-market and on-market buy-backs of up to 41.2 million Rio Tinto Limited ordinary shares. (b) In November 2017, 11,778,064 Rio Tinto Limited ordinary shares were purchased at A$63.67 per share and cancelled under an off-market share buy-back programme carried out pursuant to the shareholder approval granted at Rio Tinto Limited’s 2017 annual general meeting for off-market and on-market buy-backs of up to 42.4 million Rio Tinto Limited ordinary shares. (c) The “Special Voting Share” was issued to facilitate the joint voting by shareholders of Rio Tinto Limited and Rio Tinto plc on Joint Decisions following the DLC Merger. The “DLC Dividend Share” was issued to facilitate the efficient management of funds within the DLC structure. Directors have the ability to issue an Equalisation Share if that is required under the terms of the DLC Merger Sharing Agreement.

Other reserves and retained e_2

Other reserves and retained earnings (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Other Reserves And Retained Earnings [Abstract]
Summary of other reserves and retained earnings	2018 2017 2016 US$m US$m US$m Capital redemption reserve (a) At 1 January 38 34 34 Own shares purchased and cancelled 9 4 - At 31 December 47 38 34 Cash flow hedge reserve At 1 January 32 32 - Adjustment for transition to new accounting standards (note 45) (4 ) - - Cash flow hedge gains/(losses) 156 62 (88 ) Cash flow hedge losses/(gains) transferred to the income statement 40 (62 ) 116 Tax on the above (54 ) - 4 Transfers and other movements 25 - - At 31 December 195 32 32 Available for sale revaluation reserves At 1 January 20 (126 ) (139 ) Adjustment for transition to new accounting standards (note 45) (20 ) - - Gains on available for sale securities - 19 13 Losses on available for sale securities transferred to the income statement - 6 - Tax on the above - (1 ) - Transfers and other movements - 122 - At 31 December - 20 (126 ) Fair value through other comprehensive income reserve At 1 January - - - Adjustment for transition to new accounting standards (note 45) 8 - - Losses on equity investments (11 ) - - Transfers to retained earnings (3 ) - - At 31 December (6 ) - - Cost of hedging reserve At 1 January - - - Adjustment for transition to new accounting standards (note 45) 26 Cost of hedging deferred to reserves during the year (36 ) Transfer of cost of hedging to the income statement (3 ) - - At 31 December (13 ) - - Other reserves (b) At 1 January 11,714 11,861 11,735 Change in equity interest held by Rio Tinto - - 108 Own shares purchased from Rio Tinto Limited shareholders to satisfy share options (114 ) (64 ) (43 ) Employee share options: value of services 52 31 58 Deferred tax on share options (2 ) 10 3 Companies no longer consolidated - (124 ) - At 31 December 11,650 11,714 11,861 Foreign currency translation reserve (c) At 1 January 480 (2,585 ) (2,491 ) Parent and subsidiaries currency translation and exchange adjustments (3,658 ) 2,942 (204 ) Equity accounted units currency translation adjustments (48 ) 34 11 Currency translation reclassified on disposal 14 78 99 Transfers and other movements - 11 - At 31 December (3,212 ) 480 (2,585 ) Total other reserves per balance sheet 8,661 12,284 9,216 2018 2017 2016 US$m US$m US$m Retained earnings (d) At 1 January 23,761 21,631 19,736 Adjustment for transition to new accounting standards (note 45) (179 ) - - Parent and subsidiaries' profit for the year 13,125 8,423 4,298 Equity accounted units' profit after tax for the year 513 339 319 Actuarial gains/(losses) (e) 894 1 (94 ) Tax relating to components of other comprehensive income (269 ) (150 ) 30 Total comprehensive income for the year 14,263 8,613 4,553 Share buy-back programme (5,423 ) (2,312 ) - Dividends paid (5,356 ) (4,250 ) (2,725 ) Change in equity interest held by Rio Tinto 60 43 40 Companies no longer consolidated - 130 - Own shares purchased/treasury shares reissued for share options and other movements (140 ) (18 ) (37 ) Employee share options and other IFRS 2 charges taken to the income statement 61 57 64 Transfer from FVOCI reserve 3 - - Transfers and other movements (25 ) (133 ) - At 31 December 27,025 23,761 21,631 (a) The capital redemption reserve was set up to comply with section 733 of the UK Companies Act 2006 (previously section 170 of the UK Companies Act 1985) when shares of a company are redeemed or purchased wholly out of the company’s profits. Balances reflect the amount by which the company’s issued share capital is diminished in accordance with this section. (b) Other reserves includes US$11,936 million which represents the difference between the nominal value and issue price of the shares issued arising from Rio Tinto plc’s rights issue completed in July 2009. No share premium was recorded in the Rio Tinto plc financial statements through the operation of the merger relief provisions of the UK Companies Act 1985. Other reserves also include the cumulative amount recognised under IFRS 2 in respect of options granted but not exercised to acquire shares in Rio Tinto Limited, less, where applicable, the cost of shares purchased to satisfy share options exercised. The cumulative amount recognised under IFRS 2 in respect of options granted but not exercised to acquire shares in Rio Tinto plc is recorded in retained earnings. (c) Exchange differences arising on the translation of the Group’s net investment in foreign controlled companies are taken to the foreign currency translation reserve, as described in note 1(d). The cumulative differences relating to an investment are transferred to the income statement when the investment is disposed of. (d) Retained earnings and movements in reserves of subsidiaries include those arising from the Group’s share of joint operations. (e) There were no actuarial losses relating to equity accounted units in 2018, 2017 or 2016.

Financial instruments and ris_2

Financial instruments and risk management (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Financial Instruments [Line Items]
Summary of financial assets by categories	A (a) Financial assets and liabilities by categories IFRS 9 Fair value Fair value through other through Amortised comprehensive profit and Total cost income loss At 31 December 2018 Note US$m US$m US$m US$m Financial assets Cash and cash equivalents 21 10,773 2,779 - 7,994 Trade and other financial receivables (a) (b) 18 3,007 2,015 - 992 Equity shares and quoted funds 20 130 - 53 77 Other investments, including loans (c) 20 2,782 6 - 2,776 Derivatives related to net debt: designated as hedges (d) 20, 24 70 - - 70 Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 20 432 - - 432 Embedded derivatives not related to net debt: designated as hedges (d) 20 54 - - 54 Loans to equity accounted units including quasi equity loans 167 167 - - Total financial assets 17,415 4,967 53 12,395 Financial liabilities Trade and other financial payables (e) 25 (5,552 ) (5,513 ) (39 ) Short-term borrowings and bank overdrafts 22 (312 ) (312 ) - Medium-term and long-term borrowings 22 (12,440 ) (12,440 ) - Derivatives related to net debt: designated as hedges (d) 22, 24 (358 ) - (358 ) Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 22 (98 ) - (98 ) Embedded derivatives not related to net debt: designated as hedges (d) 22 (46 ) - (46 ) Other financial liabilities 22 (666 ) (666 ) - Total financial liabilities (19,472 ) (18,931 ) (541 ) IAS 39 Held to maturity Available assets/other Loans and for sale Held at financial Total receivables securities fair value liabilities At 31 December 2017 Note US$m US$m US$m US$m US$m Financial assets Cash and cash equivalents 21 10,550 10,550 - - - Trade and other financial receivables (a) (b) 18 2,985 2,895 - 90 - Equity shares and quoted funds 20 136 - 136 - - Other investments, including loans (c) 20 1,152 15 - 1,125 12 Derivatives related to net debt: designated as hedges (d) 20, 24 99 - - 99 - Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 20 168 - - 168 - Loans to equity accounted units including quasi equity loans 198 198 - - - Total financial assets 15,288 13,658 136 1,482 12 Financial liabilities Trade and other financial payables (e) 25 (5,922 ) (15 ) (5,907 ) Short-term borrowings and bank overdrafts 22 (552 ) - (552 ) Medium-term and long-term borrowings 22 (14,624 ) - (14,624 ) Derivatives related to net debt: designated as hedges (d) 22, 24 (276 ) (276 ) - Other derivatives and embedded derivatives: not designated as hedges (d) 22 (255 ) (255 ) - Other financial liabilities 22 (345 ) - (345 ) Total financial liabilities (21,974 ) (546 ) (21,428 ) (a) Trade and other financial receivables comprise of trade receivables, other financial receivables, and amounts due from equity accounted units within note 18. (b) Under IFRS 9, provisionally priced receivables are fair valued. In the prior year, under IAS 39, only the embedded pricing derivatives, which were separated from the host receivables, were fair valued. (c) Other investments, including loans, comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets in managed investment funds classified as held for trading. (d) These financial assets and liabilities in aggregate agree to total derivative financial instruments disclosed in notes 20 and 22. (e) Trade and other financial payables comprise trade payables, other financial payables, accruals and amounts due to equity accounted units within note 25. The trade and other payables held at fair value are valued using level 2 inputs.
Summary of financial liabilities by categories	A (a) Financial assets and liabilities by categories IFRS 9 Fair value Fair value through other through Amortised comprehensive profit and Total cost income loss At 31 December 2018 Note US$m US$m US$m US$m Financial assets Cash and cash equivalents 21 10,773 2,779 - 7,994 Trade and other financial receivables (a) (b) 18 3,007 2,015 - 992 Equity shares and quoted funds 20 130 - 53 77 Other investments, including loans (c) 20 2,782 6 - 2,776 Derivatives related to net debt: designated as hedges (d) 20, 24 70 - - 70 Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 20 432 - - 432 Embedded derivatives not related to net debt: designated as hedges (d) 20 54 - - 54 Loans to equity accounted units including quasi equity loans 167 167 - - Total financial assets 17,415 4,967 53 12,395 Financial liabilities Trade and other financial payables (e) 25 (5,552 ) (5,513 ) (39 ) Short-term borrowings and bank overdrafts 22 (312 ) (312 ) - Medium-term and long-term borrowings 22 (12,440 ) (12,440 ) - Derivatives related to net debt: designated as hedges (d) 22, 24 (358 ) - (358 ) Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 22 (98 ) - (98 ) Embedded derivatives not related to net debt: designated as hedges (d) 22 (46 ) - (46 ) Other financial liabilities 22 (666 ) (666 ) - Total financial liabilities (19,472 ) (18,931 ) (541 ) IAS 39 Held to maturity Available assets/other Loans and for sale Held at financial Total receivables securities fair value liabilities At 31 December 2017 Note US$m US$m US$m US$m US$m Financial assets Cash and cash equivalents 21 10,550 10,550 - - - Trade and other financial receivables (a) (b) 18 2,985 2,895 - 90 - Equity shares and quoted funds 20 136 - 136 - - Other investments, including loans (c) 20 1,152 15 - 1,125 12 Derivatives related to net debt: designated as hedges (d) 20, 24 99 - - 99 - Derivatives and embedded derivatives not related to net debt: not designated as hedges (d) 20 168 - - 168 - Loans to equity accounted units including quasi equity loans 198 198 - - - Total financial assets 15,288 13,658 136 1,482 12 Financial liabilities Trade and other financial payables (e) 25 (5,922 ) (15 ) (5,907 ) Short-term borrowings and bank overdrafts 22 (552 ) - (552 ) Medium-term and long-term borrowings 22 (14,624 ) - (14,624 ) Derivatives related to net debt: designated as hedges (d) 22, 24 (276 ) (276 ) - Other derivatives and embedded derivatives: not designated as hedges (d) 22 (255 ) (255 ) - Other financial liabilities 22 (345 ) - (345 ) Total financial liabilities (21,974 ) (546 ) (21,428 ) (a) Trade and other financial receivables comprise of trade receivables, other financial receivables, and amounts due from equity accounted units within note 18. (b) Under IFRS 9, provisionally priced receivables are fair valued. In the prior year, under IAS 39, only the embedded pricing derivatives, which were separated from the host receivables, were fair valued. (c) Other investments, including loans, comprise US$2,522 million (2017: US$958 million) of highly liquid financial assets in managed investment funds classified as held for trading. (d) These financial assets and liabilities in aggregate agree to total derivative financial instruments disclosed in notes 20 and 22. (e) Trade and other financial payables comprise trade payables, other financial payables, accruals and amounts due to equity accounted units within note 25. The trade and other payables held at fair value are valued using level 2 inputs.
Summary of credit ratings	The table below summarises the credit ratings attributed to the Group by Standard & Poor’s and Moody’s investor services as at 31 December. 2018 2017 Long-term rating (a) A/A3 A-/A3 Short-term rating (a) A-1/P-2 A-1/P-2 Outlook Stable/Stable Positive/Stable
Maturity analysis for non-derivative financial liabilities and derivative financial liabilities	The table below summarises the maturity profile of the Group’s financial liabilities based on contractual undiscounted payments. It will therefore not necessarily agree with the amounts disclosed in the balance sheet. Financial liability analysis At 31 December 2018 Within 1 Between Between Between Between year or on 1 and 2 2 and 3 3 and 4 4 and 5 After demand years years years years 5 years Total (Outflows)/inflows US$m US$m US$m US$m US$m US$m US$m Non-derivative financial liabilities Trade and other financial payables (5,129 ) (423 ) - - - - (5,552 ) Borrowings before swaps (312 ) (562 ) (166 ) (660 ) (741 ) (10,476 ) (12,917 ) Expected future interest payments (a) (651 ) (653 ) (636 ) (630 ) (586 ) (4,082 ) (7,238 ) Other financial liabilities (666 ) - - - - - (666 ) Derivative financial liabilities (b) Derivatives related to net debt - net settled (36 ) (36 ) (36 ) (36 ) 4 (8 ) (148 ) Derivatives related to net debt - gross settled (a) – gross inflows 48 508 39 39 39 1,278 1,951 – gross outflows (79 ) (595 ) (58 ) (58 ) (58 ) (1,581 ) (2,429 ) Derivatives not related to net debt - net settled (27 ) (13 ) (5 ) (5 ) (5 ) (28 ) (83 ) Derivatives not related to net debt - gross settled: – gross inflows 1,664 - - - - - 1,664 – gross outflows (1,733 ) - - - - - (1,733 ) Total (6,921 ) (1,774 ) (862 ) (1,350 ) (1,347 ) (14,897 ) (27,151 ) At 31 December 2017 Within 1 Between Between Between Between year or on 1 and 2 2 and 3 3 and 4 4 and 5 After demand years years years years 5 years Total (Outflows)/inflows US$m US$m US$m US$m US$m US$m US$m Non-derivative financial liabilities Trade and other financial payables (5,488 ) (434 ) - - - - (5,922 ) Borrowings before swaps (552 ) (148 ) (1,011 ) (916 ) (1,283 ) (11,387 ) (15,297 ) Expected future interest payments (a) (679 ) (673 ) (670 ) (638 ) (606 ) (4,553 ) (7,819 ) Other financial liabilities (302 ) (43 ) - - - - (345 ) Derivative financial liabilities (b) Derivatives related to net debt - net settled 10 10 14 11 7 36 88 Derivatives related to net debt - gross settled (a) – gross inflows 62 62 958 44 44 1,493 2,663 – gross outflows (82 ) (82 ) (1,051 ) (55 ) (55 ) (1,741 ) (3,066 ) Derivatives not related to net debt - net settled (43 ) (36 ) (33 ) (24 ) (21 ) (138 ) (295 ) Derivatives not related to net debt - gross settled: – gross inflows 795 - - - - - 795 – gross outflows (802 ) - - - - - (802 ) Total (7,081 ) (1,344 ) (1,793 ) (1,578 ) (1,914 ) (16,290 ) (30,000 ) (a) Interest payments have been projected using interest rates applicable at the end of the applicable financial year. Where debt is subject to variable interest rates, future interest payments are subject to change in line with market rates. (b) The maturity grouping is based on the earliest payment date.
Summary of impact of hedging instrument on statement of financial position	The impact of the hedging instrument on the Group balance sheet is as follows: At 31 December 2018 Notional amount US$m Carrying value US$m Line item in the statement of financial position Change in fair value used for measuring ineffectiveness for the period US$m Aluminium embedded derivatives separated from the power contract (a) 1,786 8 Other financial asset (US$54m) and other financial liability (US$46m) 205 (a) Aluminium embedded derivatives (forward contracts and options) are contained within certain aluminium smelter electricity purchase contracts. The impact of the hedged item on the Group balance sheet is: At 31 December 2018 Change in fair value used for measuring ineffectiveness for the period US$m Cash flow hedge reserve US$m Highly probable forecast aluminium sales (182) 179 The effect of the cash flow hedge in the statement of profit or loss and other comprehensive income (OCI) is: At 31 December 2018 Total hedging gain recognised in OCI US$m Ineffectiveness recognised in profit or loss US$m Line item in the statement of profit or loss Amount reclassified from OCI to profit or loss US$m Line item in the statement of profit or loss Highly probable forecast aluminium sales 181 24 Net operating costs (raw materials, consumables, repairs and maintenance) 2 Consolidated sales revenue
Summary of market price relevant to the aluminum purchase price swaps outstanding	Change in market prices 2018 US$m 2017 US$m Effect on net earnings +10% (102) (203) -10% 35 212 Effect on equity +10% (101) - -10% 103 -
Summary of maximum credit risk exposure of the Group's financial assets	2018 2017 Note US$m US$m Cash and cash equivalents 21 10,773 10,550 Trade and other financial receivables 18 3,007 2,985 Investments 20 2,782 1,152 Derivative assets 20 556 267 Loans to equity accounted units 38 39 Total 17,156 14,993
Summary by currency, the Group's net debt, after taking into account relevant cross currency interest rate swaps and foreign exchange contracts	The table below summarises, by currency, the Group’s net debt, after taking into account relevant cross-currency interest rate swaps and foreign exchange contracts: Total Derivatives Cash and Net cash/ Net cash/ borrowings related to net cash Other (debt) (debt) excluding overdrafts debt equivalents investments 2018 2017 Net cash/(debt) by currency US$m US$m US$m US$m US$m US$m US dollar (12,080 ) (288 ) 10,310 2,522 464 (3,628 ) Australian dollar (472 ) - 217 - (255 ) (208 ) Euro (39 ) - 17 - (22 ) (58 ) South African rand - - 95 - 95 59 Canadian dollar (157 ) - 23 - (134 ) (148 ) Other (3 ) - 110 - 107 138 Total (12,751 ) (288 ) 10,772 2,522 255 (3,845 ) Total Derivatives Cash and Net cash/ Net cash/ borrowings related to net cash Other (debt) (debt) excluding overdrafts debt equivalents investments 2018 2017 Net cash/(debt) by currency US$m US$m US$m US$m US$m US$m US dollar (12,080 ) (288 ) 10,310 2,522 464 (3,628 ) Australian dollar (472 ) - 217 - (255 ) (208 ) Euro (39 ) - 17 - (22 ) (58 ) South African rand - - 95 - 95 59 Canadian dollar (157 ) - 23 - (134 ) (148 ) Other (3 ) - 110 - 107 138 Total (12,751 ) (288 ) 10,772 2,522 255 (3,845 )
Summary of derivative financial instruments	Total fair value 2018 2017 Asset Liability Asset Liability US$m US$m US$m US$m Derivatives designated as hedges Interest rate swaps (a) 70 (137 ) 99 (127 ) Cross-currency interest rate swaps (b) - (221 ) - (149 ) Aluminium embedded derivatives (c) 54 (46 ) - - Total derivatives designated as hedges 124 (404 ) 99 (276 ) Derivatives not designated as hedges Currency forward contracts, options and swaps - (68 ) 7 (2 ) Aluminium forward contracts (d) 26 (19 ) 21 (9 ) Aluminium embedded derivatives (c) 346 - 140 (238 ) Other embedded derivatives 6 - - (5 ) Other commodity contracts 54 (11 ) - (1 ) Total derivatives not designated as hedges 432 (98 ) 168 (255 ) Total derivative instruments 556 (502 ) 267 (531 ) Analysed by maturity: Less than 1 year 88 (95 ) 29 (50 ) Between 1 and 5 years 153 (205 ) 31 (233 ) More than 5 years 315 (202 ) 207 (248 ) Total 556 (502 ) 267 (531 ) Total net derivative instruments 54 (264 ) 2018 2017 Reconciliation to balance sheet Note US$m US$m Non-current assets 20 468 238 Current assets 20 88 29 Current liabilities 22 (95 ) (50 ) Non-current liabilities 22 (407 ) (481 ) Total net derivative instruments 54 (264 ) (a) The interest rate swaps are used to convert certain fixed rate borrowings to a floating rate. For further details, see note 22. (b) The cross-currency interest rate swaps are used to convert non-US dollar denominated borrowings to either fixed or floating US dollar borrowings. For further details see note 22. (d) Aluminium embedded derivatives (forward contracts and options) are contained within certain aluminium smelter electricity purchase contracts. These contracts reduce the Group’s margin exposure to movements in the aluminium price. (c) The aluminium forward contracts are entered into to convert aluminium sales made at a fixed price to the market price (LME cash). In 2017 and 2018 these contracts were not designated as hedges.
Summary of fair value of financial instruments	The carrying amounts and fair values of all of the Group’s financial instruments which are not carried at an amount which approximates their fair value at 31 December 2018 and 31 December 2017 are shown in the following table. The fair values of the Group’s cash equivalents and loans to equity accounted units approximate their carrying values as a result of their short maturity or because they carry floating rates of interest. 31 December 2018 31 December 2017 Carrying Fair Carrying Fair value value value value Note US$m US$m US$m US$m Short-term borrowings 22 (312 ) (312 ) (552 ) (552 ) Medium-term and long-term borrowings 22 (12,440 ) (13,554 ) (14,624 ) (16,385 ) C (a) Valuation hierarchy The table below shows the financial instruments carried at fair value by valuation method, under IFRS 9, at 31 December 2018. Not held Total Level 1 (a) Level 2 (b) Level 3 (c) at fair value Note US$m US$m US$m US$m US$m Assets Cash and cash equivalents 10,773 7,994 - - 2,779 Investments in equity shares and funds 130 92 - 38 - Other investments, including loans (d) 20 2,782 2,544 - 232 6 Trade and other financial receivables (e) 18 3,007 20 972 - 2,015 16,692 10,650 972 270 4,800 Derivatives (net) Forward contracts and option contracts: designated as hedges (f) 8 - - 8 - Forward contracts and option contracts, not designated as hedges (f) 334 - (25 ) 359 - Derivatives related to net debt (Section B) (g) (288 ) - (288 ) - - Liabilities Trade and other financial payables 25 (5,552 ) - (39 ) - (5,513 ) Total 11,194 10,650 620 637 (713 ) The table below shows the financial instruments carried at fair value by valuation method, under IAS 39, at 31 December 2017. Not held Total Level 1 (a) Level 2 (b) Level 3 (c) at fair value Note US$m US$m US$m US$m US$m Assets Cash and cash equivalents 10,550 - - - 10,550 Equity shares and quoted funds 20 136 88 - 3 45 Other investments, including loans (d) 20 1,152 1,037 - 88 27 Trade and other receivables (e) 2,985 - 90 - 2,895 14,823 1,125 90 91 13,517 Derivatives (net) Forward contracts and option contracts, not designated as hedges (f) (87 ) - 11 (98 ) - Derivatives related to net debt (Section B) (g) (177 ) - (177 ) - - Liabilities Trade and other financial payables (5,922 ) - (15 ) - (5,907 ) Total 8,637 1,125 (91 ) (7 ) 7,610 (a) Valuation is based on unadjusted quoted prices in active markets for identical financial instruments. This category includes listed equity shares and other quoted funds. (b) Valuation is based either on inputs which include quoted prices for similar instruments or identical instruments in markets which are not considered to be active, or on inputs, which are directly or indirectly based on observable market data. (c) Valuation is based on inputs that are not based on observable market data (unobservable inputs). (d) Other investments, including loans, comprise: cash deposits in rehabilitation funds, government bonds, managed investment funds and royalty receivables. The royalty receivables are valued based on future expected output as well as future expected commodity prices. (e) Trade receivables include provisionally priced receivables relating to sales contracts where the selling price is determined after delivery to the customer, based on the market price at the relevant quotation point stipulated in the contract. Revenue is recognised on provisionally priced sales based on the forward selling price for the period stipulated in the contract. Under IFRS 9, provisionally priced receivables at 31 December 2018 were US$889 . (f) Level 3 derivatives consist of derivatives embedded in electricity purchase contracts linked to the LME with terms expiring between 2025 2030 338 2,426 2029 2,507 2030 (g) Interest rate and currency interest rate swaps are valued using applicable market-quoted swap yield curves adjusted for relevant basis and credit default spreads. Currency interest rate swap valuations also use market-quoted foreign exchange rates. A discounted cash flow approach is applied to the cash flows derived from the inputs to determine fair value.
Summary of capital and liquidity risk management	2018 2017 Total capital Note US$m US$m Equity attributable to owners of Rio Tinto (see Group balance sheet) 43,686 44,711 Equity attributable to non-controlling interests (see Group balance sheet) 6,137 6,404 Net debt 24 (255 ) 3,845 Total capital 49,568 54,960
Summary of effect of the cash flow hedge in statement of profit or loss and other comprehensive income (OCI)	The effect of the cash flow hedge in the statement of profit or loss and other comprehensive income (OCI) is: At 31 December 2018 Total hedging gain recognised in OCI US$m Ineffectiveness recognised in profit or loss US$m Line item in the statement of profit or loss Amount reclassified from OCI to profit or loss US$m Line item in the statement of profit or loss Highly probable forecast aluminium sales 181 24 Net operating costs (raw materials, consumables, repairs and maintenance) 2 Consolidated sales revenue
Disclosure of effect of changes in foreign exchange rates on earnings	Gains/(losses) associated with 10% strengthening of the US dollar Of which amount Closing Effect on impacting Impact exchange net underlying directly rate earnings earnings on equity Currency exposure US cents US$m US$m US$m Australian dollar 70 346 1 (993 ) Canadian dollar 73 (82 ) 7 - Euro 114 202 5 - At 31 December 2017 Gains/(losses) associated with 10% strengthening of the US dollar Of which amount Closing Effect on impacting Impact exchange net underlying directly rate earnings earnings on equity Currency exposure US cents US$m US$m US$m Australian dollar 78 608 47 (1,657 ) Canadian dollar 79 (134 ) 3 - Euro 120 165 (2 ) -
Summary of changes in the fair value of Level 3 financial assets and financial liabilities	The table below shows the summary of changes in the fair value of the Group’s level 3 financial assets and financial liabilities. 2018 2017 Level 3 financial assets Level 3 financial assets and financial liabilities and financial liabilities US$m US$m Opening balance (7 ) 479 Adjustment from transition to IFRS 9 19 - Currency translation adjustments (23 ) 8 Total realised gains/(losses) included in: – consolidated sales revenue - 1 – net operating costs 9 (5 ) Total unrealised gains/(losses) included in: - consolidated sales revenue - 17 – net operating costs (a) 375 (508 ) Total unrealised gains transferred into other comprehensive income through cash flow hedges 181 - Additions 67 - Disposals/maturity of financial instruments (6 ) (5 ) Transfers 22 6 Closing balance 637 (7 ) Total gains/(losses) for the year included in the income statement for assets and liabilities held at year end 346 (491 ) 2018 2017 Level 3 financial assets Level 3 financial assets and financial liabilities and financial liabilities US$m US$m Opening balance (7 ) 479 Adjustment from transition to IFRS 9 19 - Currency translation adjustments (23 ) 8 Total realised gains/(losses) included in: – consolidated sales revenue - 1 – net operating costs 9 (5 ) Total unrealised gains/(losses) included in: - consolidated sales revenue - 17 – net operating costs (a) 375 (508 ) Total unrealised gains transferred into other comprehensive income through cash flow hedges 181 - Additions 67 - Disposals/maturity of financial instruments (6 ) (5 ) Transfers 22 6 Closing balance 637 (7 ) Total gains/(losses) for the year included in the income statement for assets and liabilities held at year end 346 (491 )
Commodity price risk [Member]
Disclosure Of Financial Instruments [Line Items]
Summary of notional aluminium forward sales contracts embedded in power contracts	The Group is holding the following notional aluminium forward sales contracts embedded in the power contracts: At 31 December 2018 Within 1 year Between 1 and 5 years Between 5 and 10 years After 10 years Notional amount (in tonnes) 56,481 286,666 358,416 65,548 Notional amount (in US$ millions) 114 634 870 168 Average hedged rate (in US$ per tonne) 2,013 2,210 2,426 2,562

Contingencies and commitments (

Contingencies and commitments (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Commitments And Contingent Liabilities [Abstract]
Summary of capital commitments	2018 2017 US$m US$m Capital commitments excluding the Group's share of joint venture capital commitments Within 1 year 1,742 2,052 Between 1 and 3 years 439 531 Between 3 and 5 years 66 58 After 5 years 36 - Total 2,283 2,641 Group's share of joint venture capital commitments Within 1 year 115 29 Between 1 and 3 years 1 - Total 116 29
Summary of aggregate amount of minimum lease payments under non-cancellable operating leases	The aggregate amounts of minimum lease payments under non-cancellable operating leases are as follows: 2018 2017 US$m US$m Within 1 year 475 397 Between 1 and 3 years 587 542 Between 3 and 5 years 270 313 After 5 years 385 593 Total 1,717 1,845
Summary of aggregate amount of future payment commitments under purchase obligations outstanding	Adjusted (a) 2018 2017 US$m US$m Within 1 year 2,804 2,874 Between 1 and 2 years 1,565 1,712 Between 2 and 3 years 1,344 1,401 Between 3 and 4 years 1,097 1,282 Between 4 and 5 years 882 1,026 After 5 years 9,358 11,185 Total 17,050 19,480 (a)
Summary of subsidiaries and joint operations contingent liabilities	2018 2017 US$m US$m Contingent liabilities (subsidiaries and joint operations) Indemnities and other performance guarantees (a) (b) 317 552 (a) Indemnities and other performance guarantees represent the potential outflow of funds from the Group for the satisfaction of obligations including those under contractual arrangements (for example undertakings related to supplier agreements) not provided for in the balance sheet, where the likelihood of the guarantees or indemnities being called is assessed as possible rather than probable or remote. (b) There were no material contingent liabilities arising in relation to the Group’s joint ventures and associates.

Average number of employees (Ta

Average number of employees (Tables)	12 Months Ended
	Dec. 31, 2018
Number And Average Number Of Employees [Abstract]
Summary of average number of employees	Subsidiaries and joint operations Equity accounted units (Rio Tinto share) Group total 2018 2017 2016 2018 2017 2016 2018 2017 2016 Principal locations of employment: Australia and New Zealand 19,017 19,041 20,489 578 602 849 19,595 19,643 21,338 Canada 10,620 10,256 10,239 - - - 10,620 10,256 10,239 UK 287 309 487 - - - 287 309 487 Europe 1,418 1,505 1,722 - - - 1,418 1,505 1,722 Africa 3,496 3,461 4,875 1,262 1,269 1,270 4,758 4,730 6,145 US 3,792 3,429 3,196 - - - 3,792 3,429 3,196 Mongolia 2,886 2,861 2,737 - - - 2,886 2,861 2,737 Indonesia 1,615 1,642 2,862 - - - 1,615 1,642 2,862 South America 210 197 166 1,289 1,237 1,388 1,499 1,434 1,554 Other countries (a) 988 998 749 - - - 988 998 749 Total 44,329 43,699 47,522 3,129 3,108 3,507 47,458 46,807 51,029 (a) “Other countries” primarily includes employees in the Middle East (excluding Oman which is included in Africa), India, Singapore and other countries in Asia which are not shown separately in the table above. For the year ended 31 December 2018, the average number of employees in Singapore was 422 (2017: 434; 2016: 262) and the average number of employees in India was 288 (2017: 310; 2016: 280).

Principal subsidiaries (Tables)

Principal subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Significant Investments In Subsidiaries [Abstract]
Summary of Principal Subsidiaries and Financial Information for Subsidiaries	At 31 December 201 Company and country of incorporation/ operation Principal activities Class of shares held Proportion of class held (%) Group interest (%) Non-controlling interest (%) Australia Argyle Diamonds Limited Mining and processing of diamonds Ordinary 100 100 - Dampier Salt Limited Salt and gypsum Ordinary 68.36 68.36 31.64 Energy Resources of Australia Limited Uranium mining Ordinary 68.39 68.39 31.61 Hamersley Iron Pty Limited Iron ore mining Ordinary 100 100 - North Mining Limited (a) Iron ore mining Ordinary 100 100 - Queensland Coal Pty Limited (b) Coal mining Ordinary 100 100 - Rio Tinto Aluminium (Holdings) Limited Bauxite mining; alumina production; primary aluminium smelting Ordinary 100 100 - Robe River Mining Co Pty Ltd (a) Iron ore mining Class A 40 60 40 Class B 76.36 Brazil Alcan Alumina Ltda. (c) Alumina production and bauxite mining Quota 100 100 - Canada Iron Ore Company of Canada (d) Iron ore mining; iron ore pellets Common 58.72 58.72 41.28 Rio Tinto Fer et Titane Inc. Titanium dioxide feedstock; high purity iron and steel Common 100 100 - Class B preference 100 100 - CAD 0.01 preferred 100 100 - Rio Tinto Alcan Inc. Bauxite mining; alumina refining; aluminium smelting Common 100 100 - Diavik Diamond Mines (2012) Inc. (e) Diamond mining and processing Common 100 100 - Guinea Simfer Jersey Limited (f) Iron ore project Ordinary 53 53 47 Madagascar QIT Madagascar Minerals SA (g) Ilmenite mining Common 80 80 Investment certificates 100 100 15 Voting certificates 80 80 20 Mongolia Turquoise Hill Resources Ltd (including Oyu Tolgoi LLC) (h) Copper and gold mining Common 50.79 50.79 49.21 Namibia Rössing Uranium Limited ( i ) Uranium mining B N$1 71.22 68.62 31.38 C N10c 70.59 South Africa Richards Bay Titanium (Proprietary) Limited (j) Titanium dioxide;high purity iron production B Ordinary 100 B preference 100 74 26 Parent Preference 100 Richards Bay Mining (Proprietary) Limited (j) Ilmenite, rutile and zircon mining B Ordinary 100 B preference 100 74 26 Parent Preference 100 US Kennecott Holdings Corporation (including Kennecott Utah Copper and Kennecott Exploration) Copper and gold mining, smelting and refining and exploration activities Common US$0.01 100 100 - U.S. Borax Inc. Mining, refining and marketing of borates Common US$0.10 100 100 - This list includes only those companies that have a more significant impact on the profit or assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s principal subsidiaries are mostly held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) Robe River Mining Co Pty Ltd (which is 60% owned by the Group) holds a 30% interest in Robe River Iron Associates (Robe River). North Mining Ltd (which is wholly owned by the Group) holds a 35% interest in Robe River. Through these companies the Group recognises a 65% share of the assets, liabilities, revenues and expenses of Robe River, with a 12% non-controlling interest. The Group therefore has a 53% beneficial interest in Robe River. (b) Queensland Coal Pty Limited was the main legal entity that held the Group’s interests in Hail Creek (82%) and Kestrel (80%). These were unincorporated arrangements that were not entities; the Group recognised its share of assets, liabilities, revenues and expenses relating to these arrangements. On 1 August 2018, the Group sold its 82% interest in the Hail Creek coal mine and its 80% interest in the Kestrel underground coal mine. (c) Alcan Alumina Ltda holds the Group’s 10% interest in Consórcio De Alumínio Do Maranhão, a joint operation in which the Group participates but is not a joint operator. The Group recognises its share of assets, liabilities, revenues and expenses relating to this arrangement. (d) Iron Ore Company of Canada is incorporated in the US, but operates in Canada. (e) Diavik Diamond Mines (2012) Inc. (DDMI) is the legal entity that owns the Group’s 60% interest in the Diavik Joint Venture, an unincorporated arrangement. The Group recognises its share of assets, revenue and expenses relating to this arrangement. Liabilities are recognised according to DDMI’s contractual obligations, with a corresponding 40% receivable or contingent asset representing the co-owner’s share where applicable. (f) Simfer Jersey Limited, a company incorporated in Jersey in which the Group has a 53% interest, has an 85% interest in Simfer S.A. the company that operates the Simandou mining project in Guinea. The Group therefore has a 45.05% indirect interest in Simfer S.A. These entities are consolidated as subsidiaries and together referred to as the Simandou iron ore project. (g) The Group’s shareholding in QIT Madagascar Minerals SA carries an 80% economic interest and 80% of the total voting rights; a further 5% economic interest is held through non-voting investment certificates to give an economic interest of 85%. The non-controlling interests have a 15% economic interest and 20% of the total voting rights. (h) The Group has a 50.79% interest in Turquoise Hill Resources Ltd, which holds a 66% interest in Oyu Tolgoi LLC (OT) which is a subsidiary of Turquoise Hill Resources Ltd. The Group therefore has a 33.5% indirect interest in OT. Turquoise Hill Resources Ltd is incorporated in Canada but operates principally in Mongolia. ( i ) The Group’s shareholding in Rössing Uranium Limited entitles it to 35.57% of the total voting rights; the non-controlling interests hold 64.43% of the total voting rights. Rössing is consolidated by virtue of the Group’s board control. The Government of Namibia has the ability to veto matters that are considered not to be in the interest of Namibia; this is considered to be a protective right. Rio Tinto therefore has control of Rössing and consolidates it as a subsidiary. At 31 December 2018, assets and liabilities held for sale included our entire interest in Rössing Uranium Limited. (j) Additional classes of shares issued by Richards Bay Titanium (Proprietary) Limited and Richards Bay Mining (Proprietary) Limited representing non-controlling interests are not shown. The Group’s total legal and beneficial interest in Richards Bay Titanium (Proprietary) Limited and Richards Bay Mining (Proprietary) Limited is 74%. Summary financial information for subsidiaries that have non-controlling interests that are material to the Group This summarised financial information is shown on a 100% basis. It represents the amounts shown in the subsidiaries’ financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments, and before intercompany eliminations. Iron Ore Company of Canada Iron Ore Company of Canada Energy Resources of Australia Energy Resources of Australia Turquoise Hill (a)(b) Turquoise Hill (a)(b) 2018 2017 2018 2017 2018 2017 US$m US$m US$m US$m US$m US$m Revenue 1,561 1,867 151 157 1,180 940 Profit/(loss) after tax 298 377 (241 ) (29 ) 139 22 – attributable to non-controlling interests 122 156 1 (9 ) 14 (49 ) – attributable to Rio Tinto 176 221 (242 ) (20 ) 125 71 Other comprehensive (loss)/income (136 ) 144 2 - (4 ) 4 Total comprehensive income/(loss) 162 521 (239 ) (29 ) 135 26 Non-current assets 2,376 2,535 74 57 10,375 9,008 Current assets 459 714 311 406 3,813 4,953 Current liabilities (351 ) (449 ) (123 ) (128 ) (540 ) (504 ) Non-current liabilities (791 ) (838 ) (522 ) (356 ) (4,367 ) (4,311 ) Net assets/(liabilities) 1,693 1,962 (260 ) (21 ) 9,281 9,146 – attributable to non-controlling interests 699 809 (6 ) (7 ) 3,936 3,982 – attributable to Rio Tinto 994 1,153 (254 ) (14 ) 5,345 5,164 Cash flow from operations 553 840 (64 ) (2 ) 357 295 Dividends paid to non-controlling interests (178 ) (162 ) - - - - (a) Turquoise Hill Resources Ltd holds a controlling interests in OT. (b) Under the terms of the project finance facility held by OT, there are certain restrictions on the ability of OT to make shareholder distributions. Robe River Mining Co Pty Robe River Mining Co Pty Other companies and eliminations (c) Other companies and eliminations (c) Robe River Robe River 2018 2017 2018 2017 2018 2017 US$m US$m US$m US$m US$m US$m Revenue 1,082 1,164 1,262 1,351 2,344 2,515 Profit after tax 561 617 543 637 1,104 1,254 – attributable to non-controlling interests 218 242 - - 218 242 – attributable to Rio Tinto 343 375 543 637 886 1,012 Other comprehensive (loss)/income (313 ) 238 (203 ) 158 (516 ) 396 Total comprehensive income 248 855 340 795 588 1,650 Non-current assets 2,610 2,927 3,739 4,187 6,349 7,114 Current assets (d) 710 875 2,368 1,149 3,078 2,024 Current liabilities (111 ) (186 ) (235 ) (1,357 ) (346 ) (1,543 ) Non-current liabilities (d) (117 ) (174 ) (3,977 ) (2,244 ) (4,094 ) (2,418 ) Net assets 3,092 3,442 1,895 1,735 4,987 5,177 – attributable to non-controlling interests 1,237 1,375 - - 1,237 1,375 – attributable to Rio Tinto 1,855 2,067 1,895 1,735 3,750 3,802 Cash flow from operations 933 1,048 1,151 1,207 2,084 2,255 Dividends paid to non-controlling interests (224 ) (230 ) - - (224 ) (230 ) (c) “Other companies and eliminations” includes North Mining Limited (a wholly owned subsidiary of the Group which accounts for its interest in Robe River) and goodwill of US$351 million (2017: US$389 million) that arose on the Group’s acquisition of its interest in Robe River. (d) The 2017 comparative has been adjusted to more appropriately classify certain balances.

Principal joint operations (Tab

Principal joint operations (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Joint Operations [Abstract]
Summary of principle joint operations	Company and country of incorporation/operation Principal activities Group interest (%) Australia Tomago Aluminium Joint Venture Aluminium smelting 51.6 Gladstone Power Station Power generation 42.1 Hope Downs Joint Venture Iron ore mining 50 Queensland Alumina Limited (a) (b) Alumina production 80 Pilbara Iron arrangement Infrastructure, corporate and mining services (c) New Zealand New Zealand Aluminium Smelters Limited (a) (b) Aluminium smelting 79.36 Canada Aluminerie Alouette Inc. Aluminium production 40 US Pechiney Reynolds Quebec Inc (b) (d) Aluminium smelting 50.2 This list includes only those joint operations that have a more significant impact on the profit or operating assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s joint operations are held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) Although the Group has a 79.4% interest in New Zealand Aluminium Smelters Limited and an 80% interest in Queensland Alumina Limited, decisions about activities that significantly affect the returns that are generated require agreement of both parties to the arrangements, giving rise to joint control. (b) Queensland Alumina Limited, New Zealand Aluminium Smelters Limited and Pechiney Reynolds Quebec Inc. are joint arrangements that are primarily designed for the provision of output to the parties sharing joint control; this indicates that the parties have rights to substantially all the economic benefits of the assets. The liabilities of the arrangements are in substance satisfied by cash flows received from the parties; this dependence indicates that the parties in effect have obligations for the liabilities. It is these facts and circumstances that give rise to the classification of these entities as joint operations. (c) A number of arrangements are in place between the Australian Iron Ore operations managed by Rio Tinto which allow their respective assets to be operated as a single integrated network across the Pilbara region. The arrangements are managed through two wholly owned subsidiaries: Pilbara Iron (Company) Services Pty Ltd and Pilbara Iron Pty Ltd. In assessing the Pilbara Iron arrangements, it has been concluded that they collectively constitute a joint operation on the basis that decisions about relevant activities require unanimous consent. The resulting efficiencies are shared between Rio Tinto and Robe River Iron Associates (Robe River), and the parties fund all of the cash flow requirements of Pilbara Iron (Company) Services Pty Ltd and Pilbara Iron Pty Ltd. (d) Pechiney Reynolds Quebec Inc. has a 50.1% interest in the Aluminerie de Bécancour, Inc. aluminium smelter, which is located in Canada.

Principal joint ventures (Table

Principal joint ventures (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Joint Ventures [Abstract]
Summary of principal joint ventures	At 31 December 201 Company and country of incorporation/operation Principal activities Number of Class of Proportion Group Chile Minera Escondida Limitada (a) Copper mining and refining - - - 30 Oman Sohar Aluminium Co. L.L.C. (b) Aluminium smelting; power generation 37,500 Ordinary 20 20 This list includes only those joint ventures that have a more significant impact on the profit or operating assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s principal joint ventures are held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) Although the Group has a 30% interest in Minera Escondida Limitada, participant and management agreements provide for an Owners’ Council whereby significant commercial and operational decisions about the relevant activities that significantly affect the returns that are generated in effect require the joint approval of both Rio Tinto and BHP Billiton (holders of a 57.5% interest). It is therefore determined that Rio Tinto has joint control. The year end of Minera Escondida Limitada is 30 June. The amounts included in the consolidated financial statements of Rio Tinto are, however, based on accounts of Minera Escondida Limitada that are coterminous with those of the Group. (b) Although the Group holds a 20% interest in Sohar Aluminium Co. L.L.C., decisions about relevant activities that significantly affect the returns that are generated require agreement of all parties to the arrangement. It is therefore determined that Rio Tinto has joint control. Summary information for joint ventures that are material to the Group This summarised financial information is shown on a 100% basis. It represents the amounts shown in the joint ventures’ financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments and amounts due to and from Rio Tinto. Minera Minera Sohar Sohar Escondida Escondida Aluminium Aluminium Limitada (a) Limitada (a) Co. L.L.C. (b) Co. L.L.C. (b) 2018 2017 2018 2017 US$m US$m US$m US$m Revenue 7,580 6,037 810 460 Depreciation and amortisation (1,727 ) (1,690 ) (120 ) (145 ) Other operating costs (3,230 ) (2,617 ) (440 ) (205 ) Operating profit 2,623 1,730 250 110 Finance expense (163 ) (120 ) (35 ) (35 ) Income tax (873 ) (627 ) (40 ) - Profit after tax 1,587 983 175 75 Total comprehensive income 1,587 983 175 75 Non-current assets 13,027 13,814 3,085 3,230 Current assets 2,413 2,760 340 305 Current liabilities (1,637 ) (1,727 ) (230 ) (205 ) Non-current liabilities (4,460 ) (4,617 ) (955 ) (1,270 ) Net assets 9,343 10,230 2,240 2,060 Assets and liabilities above include: – c ash and cash equivalents 697 460 15 95 – current financial liabilities (230 ) (330 ) (100 ) (130 ) – non-current financial liabilities (2,763 ) (2,840 ) (795 ) (1,120 ) Dividends received from joint venture (Rio Tinto share) 786 780 - - Reconciliation of the above amounts to the investment recognised in the Group balance sheet Group interest 30 % 30 % 20 % 20 % Net assets 9,343 10,230 2,240 2,060 Group's ownership interest 2,803 3,069 448 412 Other adjustments - 4 (1 ) (3 ) Carrying value of Group's interest 2,803 3,073 447 409 (a) In addition to its “Investment in equity accounted units”, the Group recognises deferred tax liabilities of US$413 million (2017: US$500 million) relating to tax on unremitted earnings of equity accounted units. (b) Under covenants stipulated in the agreement to Sohar Aluminium Co. L.L.C.’s secured loan facilities, Sohar Aluminium Co. L.L.C. is currently restricted from making any shareholder distributions until 2021 unless a specified amount of the loan facilities is funded.

Principal associates (Tables)

Principal associates (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Significant Investments In Associates [Abstract]
Summary of principal associates	At 31 December 201 Company and country of incorporation/operation Principal activities Number of shares held Class of shares held Proportion of class held (%) Group interest (%) Australia Boyne Smelters Limited (a) Aluminium smelting 153,679,560 Ordinary 59.4 59.4 Brazil Mineração Rio do Norte S.A. (b) Bauxite mining 25,000,000,000 Ordinary 12.5 12 47,000,000,000 Preferred 11.75 US Halco (Mining) Inc. (c) 4,500 Common 45 45 This list includes only those associates that have a more significant impact on the profit or operating assets of the Group. Refer to note 47 for a list of related undertakings. The Group’s principal associates are held by intermediate holding companies and not directly by Rio Tinto plc or Rio Tinto Limited. (a) The parties that collectively control Boyne Smelters Limited do so through decisions that are determined on an aggregate voting interest that can be achieved by several combinations of the parties. Although each combination requires Rio Tinto’s approval, this is not joint control as defined under IFRS 11. Rio Tinto is therefore determined to have significant influence over this company. (b) Although the Group holds only 12% of Mineração Rio do Norte S.A., it has representation on its board of directors and a consequent ability to participate in the financial and operating policy decisions. It is therefore determined that Rio Tinto has significant influence. (c) Halco (Mining) Inc. has a 51% indirect interest in Compagnie des Bauxites de Guinée, a bauxite mine, the core assets of which are located in Guinea. Summary information for associates that are material to the Group This summarised financial information is shown on a 100% basis. It represents the amounts shown in the associate’s financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments and amounts due to and from Rio Tinto. Boyne Boyne Smelters Smelters Limited (a) Limited (a) 2018 2017 US$m US$m Revenue - - (Loss)/profit after tax (12 ) 5 Other comprehensive (loss)/income (b) (68 ) 56 Total comprehensive (loss)/income (80 ) 61 Non-current assets 1,268 1,468 Current assets 93 88 Current liabilities (113 ) (99 ) Non-current liabilities (842 ) (996 ) Net assets 406 461 Reconciliation of the above amounts to the investment recognised in the Group balance sheet
Reconciliation of financial information for principal associates by carrying value	Group interest 59.4 % 59.4 % Net assets 406 461 Group's ownership interest 241 274 Loans to equity accounted units 129 159 Carrying value of Group's interest 370 433 (a) Boyne Smelters Limited is a tolling operation; as such it is dependent on its participants for funding which is provided through cash calls. Rio Tinto has made certain prepayments to Boyne for toll processing of alumina. These are charged to Group operating costs as processing takes place. (b) “Other comprehensive (loss)/income” is net of amounts recognised by subsidiaries in relation to quasi equity loans.
Summary information for joint ventures and associates that are not individually material to the group	Summary information for joint ventures and associates that are not individually material to the Group Joint Joint ventures ventures Associates Associates 2018 2017 2018 2017 US$m US$m US$m US$m Carrying value of Group's interest - - 679 571 Profit after tax - - 9 25 Other comprehensive income - - (23 ) 14 Total comprehensive income - - (14 ) 39

Directors' and key management_2

Directors' and key management remuneration (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Information About Key Management Personnel [Abstract]
Summary of aggregate remuneration	Aggregate remuneration, calculated in accordance with the UK Companies Act 2006, of the directors of the parent companies was as follows: 2018 US$’000 2017 US$’000 2016 US$’000 Emoluments 9,069 8,339 9,186 Long term incentive plans 2,923 4,685 3,071 11,992 13,024 12,257 Pension contributions: defined contribution plans 80 135 69 Gains made on exercise of share options 107 - -
Summary of aggregate compensation, representing the expense	Aggregate compensation, representing the expense recognised under IFRS, as defined in note 1, of the Group’s key management, including directors, was as follows: 2018 US$’000 2017 US$’000 2016 US$’000 Short-term employee benefits and costs 23,978 23,095 22,269 Post-employment benefits 629 415 3,461 Employment termination benefits 69 - 2,682 Share-based payments 14,916 8,033 15,806 Total 39,592 31,543 44,218

Auditors' remuneration (Tables)

Auditors' remuneration (Tables)	12 Months Ended
	Dec. 31, 2018
Auditors Remuneration [Abstract]
Auditors' remuneration	2018 US$m 2017 US$m 2016 US$m Group Auditors’ remuneration (a) Audit of the Group 9.2 6.2 4.5 Audit of subsidiaries 7.5 8.1 9.0 Total audit 16.7 14.3 13.5 Audit-related assurance service 0.9 1.0 0.9 Other assurance services (b) 3.3 2.3 0.6 Total assurance services 4.2 3.3 1.5 Tax compliance (c) - 0.3 0.5 Tax advisory services (c) - 0.2 0.1 Other non-audit services not covered above 0.2 0.7 1.8 Total non-audit services 4.4 4.5 3.9 Total Group Auditors’ remuneration 21.1 18.8 17.4 Audit fees payable to other accounting firms Audit of the financial statements of the Group’s subsidiaries 1.4 2.0 2.1 Fees in respect of pension scheme audits 0.1 0.5 0.3 Total audit fees payable to other accounting firms 1.5 2.5 2.4 (a) The remuneration payable to PwC, the Group Auditors, is approved by the Audit Committee. The Committee sets the policy for the award of non-audit work to the auditors and approves the nature and extent of such work, and the amount of the related fees, to ensure that independence is maintained. The fees disclosed above consolidate all payments made to member firms of PwC by the companies and their subsidiaries, along with fees in respect of joint operations paid for by the Group. Non-audit services arise largely from assurance and/or regulation related work. Also included in amounts above are US$0.1 million for audits relating to associated pension schemes of the company and US$0.1 million of non-audit services relating to associated pension schemes. (b) Other assurance services relates to the review of non-statutory financial information including sustainability reporting. (c) Tax compliance and tax advisory services incurred in the year amounted to US$0.04 million.

Related-party transactions (Tab

Related-party transactions (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Summary of transactions and balances with equity accounted units	Transactions and balances with equity accounted units are summarised below. Purchases, trade and other receivables, and trade and other payables relate largely to amounts charged by equity accounted units for toll processing of alumina and purchasing of bauxite and aluminium. Sales relate largely to sales of alumina to equity accounted units for smelting into aluminium. 2018 2017 2016 Income statement items Note US$m US$m US$m Purchases from equity accounted units (1,209 ) (993 ) (1,216 ) Sales to equity accounted units 493 210 248 Cash flow statement items US$m US$m US$m Dividends from equity accounted units 800 817 253 Net funding of equity accounted units (9 ) (3 ) (12 ) Balance sheet items US$m US$m US$m Investments in equity accounted units (a) 15 4,299 4,486 5,019 Loans to equity accounted units 20 38 39 39 Loans from equity accounted units 22 - (31 ) (49 ) Trade and other receivables: amounts due from equity accounted units (b) 18 278 299 298 Trade and other payables: amounts due to equity accounted units 25 (223 ) (175 ) (243 ) (a) Investments in equity accounted units include quasi equity loans. Further information about investments in equity accounted units is set out in notes 35 and 36. (b) This includes prepayments of tolling charges.

Exchange rates in US$ (Tables)

Exchange rates in US$ (Tables)	12 Months Ended
	Dec. 31, 2018
Foreign Exchange Rates [Abstract]
Summary of principal exchange rate used in preparation of financial statements	The principal exchange rates used in the preparation of the 2018 financial statements were: Full-year average Year-end 2018 2017 2016 2018 2017 2016 Sterling 1.34 1.29 1.36 1.27 1.34 1.22 Australian dollar 0.75 0.77 0.74 0.70 0.78 0.72 Canadian dollar 0.77 0.77 0.76 0.73 0.79 0.74 Euro 1.18 1.13 1.11 1.14 1.20 1.05 South African rand 0.076 0.075 0.068 0.069 0.081 0.073

Share-based payments (Tables)

Share-based payments (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Charge has been recognised in income statement for Rio Tinto's share-based incentive plans, and the related liability (for cash-settled plans)	The charge that has been recognised in the income statement for Rio Tinto’s share-based incentive plans, and the related liability (for cash-settled plans), is set out in the table below. Charge recognised for the year Liability at the end of the year 2018 2017 2016 2018 2017 US$m US$m US$m US$m US$m Equity-settled plans 118 88 116 - - Cash-settled plans 4 3 - 16 15 Total 122 91 116 16 15
Summary of options outstanding and exercisable	A summary of the status of the companies’ equity-settled share option plans at 31 December 2018 is presented below. Options outstanding and exercisable at 31 December 2018 Number Weighted average exercise price per option £/A$ Weighted average remaining contractual life Years Aggregate intrinsic value 2018 US$m Rio Tinto plc Share Option Plan (exercise price £16 – £25) 23,659 17 0.22 1 Rio Tinto Limited Share Option Plan (exercise price A$33) 16,455 33 0.21 - 40,114 1
Performance share plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Summary of non-vested and vested shares	Performance Share Awards (granted under either the Performance Share Plans or the Equity Incentive Plans) Rio Tinto plc awards Rio Tinto Limited awards 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 Non-vested shares at 1 January 3,555,274 20.47 2,883,053 18.27 1,609,154 40.13 1,590,957 37.52 Awarded 801,047 26.87 1,198,677 24.64 387,298 53.85 529,776 45.84 Forfeited (188,761) 21.45 (199,435) 16.28 (36,530) 43.83 (36,716) 36.59 Failed performance conditions (107,625) 14.54 (161,966) 16.25 (54,322) 27.67 (113,857) 30.89 Vested (214,853) 21.57 (165,055) 21.51 (108,321) 40.85 (84,284) 40.79 Transfers from equity to cash-settled (a) - - - - - - (276,722) 40.11 Non-vested shares at 31 December 3,845,082 21.86 3,555,274 20.47 1,797,279 43.34 1,609,154 40.13 2018 number Weighted average share price 2018 2017 number Weighted average share price 2017 2018 number Weighted average share price 2018 2017 number Weighted average share price 2017 Vested awards settled in shares during the year (including dividend shares applied on vesting) 248,965 42.57 188,383 31.04 105,374 82.97 73,311 63.09 Vested awards settled in cash during the year (including dividend shares applied on vesting) 991 42.40 - - 9,959 82.08 5,010 62.81 (a) In 2017, an agreement was reached between the Group and a former director to settle any of his future vested awards in cash rather than equity.
Share Incentive Plans
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Summary of non-vested and vested shares	Notes to the 2018 financial statements continued 43 Share-based payments continued Management Share Awards, Bonus Deferral Awards (granted under the Management Share Plans, Bonus Deferral Plans or Equity Incentive Plans), Global Employee Share Plans and UK Share Plan (combined) Rio Tinto plc awards (a) Rio Tinto Limited awards 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 Non-vested awards at 1 January 3,473,092 27.23 3,305,966 26.00 2,933,237 54.15 2,986,080 53.32 Awarded 1,135,103 39.49 1,499,374 32.50 943,315 78.36 1,156,078 61.05 Forfeited (250,853) 30.26 (159,669) 29.46 (185,062) 64.60 (127,905) 53.61 Cancelled (33,563) 26.52 (51,773) 25.82 (36,613) 52.84 (95,203) 51.18 Vested (1,281,759) 27.54 (1,120,806) 30.41 (1,040,947) 55.30 (985,813) 60.06 Non-vested shares at 31 December 3,042,020 31.43 3,473,092 27.23 2,613,930 61.71 2,933,237 54.15 Comprising: – Management Share Awards 1,666,082 32.52 1,897,318 27.99 1,520,292 64.06 1,617,838 55.42 – Bonus Deferral Awards 203,900 37.86 281,994 25.53 127,423 71.93 153,966 52.83 – Global Employee Share Plan 1,102,322 28.68 1,196,937 26.42 966,215 56.66 1,161,433 52.54 – UK Share Plan 69,716 29.90 96,843 27.14 - - - - 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 2018 number Weighted average fair value at grant date 2018 2017 number Weighted average fair value at grant date 2017 Vested awards settled in shares during the year (including dividend shares applied on vesting): – Management Share Awards 669,678 40.03 653,776 35.33 570,173 80.87 577,083 67.93 – Bonus Deferral Awards 221,198 37.69 170,036 34.44 108,001 75.36 88,644 69.98 – Global Employee Share Plan 451,710 39.06 382,585 33.56 473,420 78.78 466,308 65.10 – UK Share Plan 16,968 38.21 11,120 34.56 - - - - (a) Awards of Rio Tinto American Depository Receipts (ADRs) under the Global Employee Share Plan are included within the totals for Rio Tinto plc awards for the purpose of these tables.

Post-retirement benefits (Table

Post-retirement benefits (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Pension And Post Retirement Healthcare Plans [Abstract]
Summary of fair value of plan assets	The proportions of the total fair value of assets in the pension plans for each asset class at the balance sheet date were: 2018 2017 Equities 20.7% 32.4% – Quoted 16.7% 28.6% – Private 4.0% 3.8% Bonds 63.6% 53.2% – Government fixed income 18.0% 14.3% – Government inflation-linked 15.5% 13.1% – Corporate and other publicly quoted 27.1% 23.5% – Private 3.0% 2.3% Property 11.0% 11.2% – Quoted property funds 5.1% 5.8% – Unquoted property funds 5.9% 5.4% Qualifying insurance policies 0.1% 0.2% Cash and other 4.6% 3.0% Total 100.0% 100.0%
Summary of maturity of defined benefit obligations	An approximate analysis of the maturity of the obligations is given in the table below: Pension benefits Other benefits 2018 Total % 2017 Total % 2016 Total % Proportion relating to current employees 20% 15% 19% 20% 21% Proportion relating to former employees not yet retired 11% 2% 11 % 11% 12% Proportion relating to retirees 69% 83% 70 % 69% 67% Total 100% 100% 100 % 100% 100% Average duration of obligations (years) 13.4 12.7 13.4 13.9 14.3
Summary of geographical distribution of defined benefit obligations	An approximate analysis of the geographic distribution of the obligations is given in the table below: Pension benefits Other benefits 2018 Total % 2017 Total % 2016 Total % Canada 49% 39% 48 % 49% 46% UK 30% 2% 28 % 27% 27% US 11% 56% 14 % 14% 16% Switzerland 5% 0% 5 % 5% 5% Other 5% 3% 5 % 5% 6% Total 100% 100% 100 % 100% 100%
Summary of total expense recognised in the income statement	Total expense recognised in the income statement Pension benefits Other benefits 2018 Total US$m 2017 Total US$m 2016 Total US$m Current employer service cost for defined benefit plans (156) (9) (165) (155) (158) Past service (cost)/income (34) (2) (36) 4 - Curtailment gains 2 - 2 1 5 Settlement gains 5 - 5 1 - Net interest on net defined benefit liability (44) (35) (79) (79) (90) Non-investment expenses paid from the plans (15) - (15) (17) (22) Total defined benefit expense (242) (46) (288) (245) (265) Current employer service cost for defined contribution and industry-wide plans (242) (2) (244) (255) (257) Total expense recognised in the income statement (484) (48) (532) (500) (522)
Summary of total amount recognised in other comprehensive income before tax	Total amount recognised in other comprehensive income before tax 2018 US$m 2017 US$m 2016 US$m Actuarial gains/(losses) 1,382 (855) (1,120) Return on assets (net of interest on assets) (527) 894 1,031 Gain/(loss) on application of asset ceiling 52 (33) (1) Total gain/(loss) recognised in other comprehensive income 907 6 (90)
Summary of amount recognised in balance sheet	The following amounts were measured in accordance with IAS 19 at 31 December: Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Total fair value of plan assets 13,203 - 13,203 15,257 Present value of obligations – funded (13,482) - (13,482) (16,199) Present value of obligations – unfunded (401) (871) (1,272) (1,446) Present value of obligations – total (13,883) (871) (14,754) (17,645) Effect of asset ceiling - - - (111) Net deficit to be shown in the balance sheet (680) (871) (1,551) (2,499) Comprising: – Deficits (1,615) (871) (2,486) (3,370) – Surpluses 935 - 935 871 Net deficits on pension plans (680) - (680) (1,501) Unfunded post-retirement healthcare obligation - (871) (871) (998)
Summary of funding policy and contributions to plans	Pension benefits Other benefits 2018 Total US$m 2017 Total US$m 2016 Total US$m Contributions to defined benefit plans 204 44 248 404 464 Contributions to defined contribution plans 242 2 244 243 240 Contributions to industry-wide plans - - - 12 17 Total 446 46 492 659 721
Summary of movement in net defined benefit liability	Defined contribution plans and industry-wide plans are excluded from the movements below. Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in the net defined benefit liability Net defined benefit liability at the start of the year (1,501) (998) (2,499) (2,542) Amounts recognised in Income statement (242) (46) (288) (245) Amounts recognised in Other comprehensive income 812 95 907 6 Employer contributions 204 44 248 404 Arrangements divested (10) - (10) 13 Currency exchange rate loss 57 34 91 (135) Net defined benefit liability at the end of the year (680) (871) (1,551) (2,499) Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in present value of obligation Present value of obligation at the start of the year (16,647) (998) (17,645) (16,228) Current employer service costs (156) (9) (165) (155) Past service (cost)/income (34) (2) (36) 4 Curtailments 2 - 2 1 Settlements 299 - 299 307 Interest on obligation (468) (35) (503) (532) Contributions by plan participants (24) - (24) (23) Benefits paid 871 44 915 949 Experience gains 11 21 32 7 Changes in financial assumptions gain/(loss) 1,276 73 1,349 (718) Changes in demographic assumptions gain/(loss) - 1 1 (144) Arrangements divested 94 - 94 13 Currency exchange rate gain/(loss) 893 34 927 (1,126) Present value of obligation at the end of the year (13,883) (871) (14,754) (17,645) Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in plan assets Fair value of plan assets at the start of the year 15,257 - 15,257 13,749 Settlements (294) - (294) (306) Interest on assets 434 - 434 459 Contributions by plan participants 24 - 24 23 Contributions by employer 204 44 248 404 Benefits paid (871) (44) (915) (949) Non-investment expenses (15) - (15) (17) Return on plan assets (net of interest on assets) (527) - (527) 894 Arrangements divested (161) - (161) - Currency exchange rate (loss)/gain (848) - (848) 1,000 Fair value of plan assets at the end of the year 13,203 - 13,203 15,257 Pension benefits Other benefits 2018 Total US$m 2017 Total US$m Change in the effect of the asset ceiling Effect of the asset ceiling at the start of the year (111) - (111) (63) Interest on the effect of the asset ceiling (10) - (10) (6) Movement in the effect of the asset ceiling 52 - 52 (33) Arrangements divested and other transfers 57 - 57 - Currency exchange rate gain/(loss) 12 - 12 (9) Effect of the asset ceiling at the end of the year - - - (111)
Summary of main assumptions rate for valuations of plans and sensitivity analysis	The main assumptions for the valuations of the plans under IAS 19 are set out below. Canada UK US Switzerland At 31 December 2018 Discount rate 3.9% 2.8% 4.2% 0.7% Inflation (a) 1.6% 3.3% 2.0% 1.2% Rate of increase in pensions 0.2% 2.9% 0.0% 0.0% Rate of increase in salaries 2.9% 3.7% 3.5% 2.2% At 31 December 2017 Discount rate 3.4% 2.3% 3.5% 0.5% Inflation (a) 1.8% 3.2% 2.1% 1.2% Rate of increase in pensions 0.5% 2.8% 0.0% 0.4% Rate of increase in salaries 3.1% 3.6% 3.6% 2.2% (a) The inflation assumption shown for the UK is for the Retail Price Index. The assumption for the Consumer Price Index at 31 December 2018 was 2.2% (2017: 2.1%). 2018 2017 Approximate Approximate Assumption Change in assumption Pensions US$m Other US$m Pensions US$m Other US$m Discount rate Increase of 0.5 percentage points 782 51 1,091 59 Decrease of 0.5 percentage points (832) (55) (1,169) (63) Inflation Increase of 0.5 percentage points (389) (17) (579) (20) Decrease of 0.5 percentage points 369 15 550 18 Salary increases Increase of 0.5 percentage points (46) (1) (74) (1) Decrease of 0.5 percentage points 45 1 72 1 Demographic – allowance for future improvements in longevity Participants assumed to have the mortality rates of individuals who are one year older 381 18 509 20 Participants assumed to have the mortality rates of individuals who are one year younger (381) (18) (509) (20)

New Standards and Interpretat_2

New Standards and Interpretations Adopted in the Current Year (Tables)	12 Months Ended
	Dec. 31, 2018
Description Of Expected Impact Of Initial Application Of New Standards Or Interpretations [Abstract]
Schedule of impact on Equity attributable to owners of Rio Tinto on the adoption of IFRS 9 and IFRS 15	The impact on equity attributable to owners of Rio Tinto as at 1 January 2018 of the adoption of IFRS 9 and IFRS 15 is as follows: US$m Equity attributable to owners of Rio Tinto as at 31 December 2017 44,711 IFRS 9 Impairment provision resulting from application of the Expected Credit Loss (ECL) model and revaluations (5) IFRS 15 De-recognition of receivable arising from “uplift” transaction (see page 222) (164) Restated equity attributable to owners of Rio Tinto as at 1 January 2018 44,542 Financial assets have been classified into the appropriate IFRS 9 categories below. Refer to note 1 for the Group’s revised financial asset classification and measurement policies. IFRS 9 classification at 1 January 2018 Held at FVPL Held at FVOCI (designated) Held at amortised cost IAS 39 classification at 1 January 2018 Total Held for trading Available-for-sale Loans & receivable, Held-to-maturity US$m US$m US$m US$m Opening balance – IAS 39 15,288 1,482 136 13,670 Cash and cash equivalents (a) (b) Reclassification of money market funds from amortised cost to FVPL - 7,813 - (7,813) Trade and other receivables (b) (c) Reclassification of trade and other receivables from amortised cost to FVPL - 1,316 - (1,316) Investments in equity shares and funds (d) Reclassification of investments from available-for-sale to FVPL - 90 (90) - Other investment including loans Reclassification of a financial asset from held-to-maturity to FVPL - 6 - (6) Opening balance – IFRS 9 (excluding expected credit losses and revaluation of funds) 15,288 10,707 46 4,535 Impairment provision resulting from the application of the ECL model (7) Revaluation of funds 1 Opening balance – IFRS 9 (including expected credit losses and revaluation of funds) 15,282
Schedule of impact of transition to IFRS 9 on the Group’s opening retained earnings	The impact of transition to IFRS 9 on the Group’s opening retained earnings as at 1 January 2018 is as follows: US$m Closing retained earnings 31 December 2017 23,761 Costs of hedging adjustment (22) Reclassification of equity investments from available-for-sale to FVPL 12 Impairment provision resulting from the application of the ECL model (7) Tax impact 1 Revaluation of funds 1 Adjustment to retained earnings from adoption of IFRS 9 on 1 January 2018 (sub-total) (15) Opening retained earnings 1 January 2018 – IFRS 9 (before restatement for IFRS 15) 23,746
Summary of retained earnings and reserves	B Retained earnings and reserves Effect on Available-for-sale (AfS) reserve Effect on FVOCI reserve Costs of hedging reserve Cash flow hedge reserve Effect on retained earnings US$m US$m US$m US$m US$m Closing balance – 31 December 2017 20 - - 32 23,761 Reclassification of equity investments from AfS (e) (20) 8 - - 12 Impact of costs of hedging adjustment (f) - - 26 (4) (22) Impairment provisions (g) - - - - (7) Tax impact - - - - 1 Re-measurement of funds - - - - 1 Total impact (20) 8 26 (4) (15) Opening balance – 1 January 2018 - 8 26 28 23,746 (e) The Group has elected to classify certain equity investments as fair value through OCI. (f) The costs of hedging adjustment is explained in C below. (g) The impairment provision is explained in D below.

Rio Tinto financial informati_2

Rio Tinto financial information by business unit (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Financial Information By Business Unit [Abstract]
Schedule of financial information by business unit	Gross revenue (a) EBITDA (b) Net earnings (c) for the year ended 31 December for the year ended 31 December for the year ended 31 December Rio Tinto interest 2018 2017 2016 2018 2017 2016 2018 2017 2016 % US$m US$m US$m US$m US$m US$m US$m US$m US$m Iron Ore Pilbara (d) 18,359 18,143 14,530 11,267 11,383 8,558 6,460 6,576 4,662 Evaluation projects/other 126 108 75 58 137 (32 ) 54 116 (51 ) Total Iron Ore 18,485 18,251 14,605 11,325 11,520 8,526 6,514 6,692 4,611 Aluminium (e) Bauxite 2,324 2,019 1,913 790 804 848 412 463 493 Alumina 3,340 2,661 2,118 1,137 454 27 634 180 (121 ) Intrasegment (861 ) (790 ) (786 ) (7 ) (25 ) - (5 ) (17 ) - Bauxite & Alumina 4,803 3,890 3,245 1,920 1,233 875 1,041 626 372 Primary Metal 6,468 5,808 4,913 1,418 1,762 1,258 595 778 402 Pacific Aluminium 2,541 2,305 1,971 148 453 264 - 176 62 Inter-segment and other (3,226 ) (2,321 ) (1,822 ) (88 ) (19 ) (50 ) (67 ) (12 ) (13 ) Integrated operations 10,586 9,682 8,307 3,398 3,429 2,347 1,569 1,568 823 Other product group items 1,479 1,214 1,075 (440 ) (132 ) (42 ) (344 ) (100 ) (30 ) Product group operations 12,065 10,896 9,382 2,958 3,297 2,305 1,225 1,468 793 Evaluation projects/other 126 109 76 137 126 167 122 115 154 Total Aluminium 12,191 11,005 9,458 3,095 3,423 2,472 1,347 1,583 947 Copper & Diamonds Rio Tinto Kennecott 100.0 1,862 1,352 1,243 785 539 126 293 78 (228 ) Escondida 30.0 2,274 1,811 1,465 1,301 1,030 793 506 325 270 Grasberg joint venture (g) 457 33 - 281 (3 ) (17 ) 217 (169 ) (64 ) Oyu Tolgoi and Turquoise Hill (h) 1,180 940 1,203 375 256 436 69 36 52 Diamonds (i) 695 706 613 301 287 239 118 92 47 Product group operations 6,468 4,842 4,524 3,043 2,109 1,577 1,203 362 77 Evaluation projects/other - - - (267 ) (205 ) (190 ) (149 ) (99 ) (95 ) Total Copper & Diamonds 6,468 4,842 4,524 2,776 1,904 1,387 1,054 263 (18 ) Energy & Minerals Rio Tinto Coal Australia (j) 989 2,829 2,634 893 1,223 893 591 716 382 Iron Ore Company of Canada 58.7 1,583 1,867 1,324 586 770 335 166 235 64 Rio Tinto Iron & Titanium (k) 1,782 1,763 1,419 510 546 370 174 201 86 Rio Tinto Borates 100.0 622 630 620 197 244 213 111 126 117 Dampier Salt 68.4 246 215 259 56 27 74 18 3 25 Uranium (l) 415 417 456 18 15 54 (4 ) (26 ) 10 Product group operations 5,637 7,721 6,712 2,260 2,825 1,939 1,056 1,255 684 Simandou iron ore project (m) - - - (15 ) (13 ) (102 ) (7 ) (6 ) (47 ) Evaluation projects/other 60 43 22 (52 ) (9 ) (31 ) (37 ) (7 ) (25 ) Total Energy & Minerals 5,697 7,764 6,734 2,193 2,803 1,806 1,012 1,242 612 Other operations (n) 9 10 8 (70 ) (116 ) (95 ) (102 ) (138 ) (88 ) Inter-segment transactions (15 ) (15 ) (11 ) - - - - - - Product group total 42,835 41,857 35,318 19,319 19,534 14,096 9,825 9,642 6,064 Central pension costs, share-based payments and insurance (128 ) (68 ) (34 ) (90 ) (48 ) (24 ) Restructuring, project and one-off costs (272 ) (177 ) (13 ) (190 ) (124 ) (9 ) Central costs (552 ) (491 ) (364 ) (410 ) (311 ) (208 ) Exploration and evaluation (231 ) (218 ) (175 ) (193 ) (178 ) (147 ) Net interest (134 ) (354 ) (576 ) Underlying EBITDA/earnings 18,136 18,580 13,510 8,808 8,627 5,100 Items excluded from underlying EBITDA/earnings - 10 18 5,127 1,912 (687 ) 4,830 135 (483 ) EBITDA/net earnings 23,263 20,492 12,823 13,638 8,762 4,617 Reconciliation to Group income statement Share of equity accounted unit sales and intra-subsidiary/equity accounted unit sales (2,313 ) (1,837 ) (1,555 ) Depreciation and amortisation in subsidiaries excluding capitalised depreciation (3,909 ) (4,302 ) (4,691 ) Impairment charges (132 ) (796 ) (249 ) Depreciation and amortisation in equity accounted units (650 ) (648 ) (526 ) Taxation and finance items in equity accounted units (372 ) (272 ) (241 ) Consolidated sales revenue/profit on ordinary activities before finance items and taxation 40,522 40,030 33,781 18,200 14,474 7,116 Depreciation and Capital expenditure (o) amortisation Operating assets (p) Employees for the year ended 31 December for the year ended 31 December as at for the year ended 31 December Rio Tinto interest 2018 2017 2016 2018 2017 2016 2018 2017 2016 2018 2017 2016 % US$m US$m US$m US$m US$m US$m US$m US$m US$m Number Number Number Iron Ore Pilbara (d) 1,288 1,201 868 1,682 1,645 1,645 14,486 16,535 16,357 10,422 10,159 10,424 Evaluation projects/other - - - - - - 2 2 2 - - - Total Iron Ore 1,288 1,201 868 1,682 1,645 1,645 14,488 16,537 16,359 10,422 10,159 10,424 Aluminium (e) Bauxite 953 825 343 165 123 110 2,494 1,897 1,278 2,676 2,534 2,592 Alumina 218 108 87 194 209 206 2,721 2,733 2,588 2,009 2,012 2,139 Intrasegment - - - - (20 ) (18 ) - - - - Bauxite & Alumina 1,171 933 430 359 332 316 5,195 4,612 3,866 4,685 4,546 4,731 Primary Metal 595 389 394 615 665 716 9,306 9,946 10,701 6,497 6,404 6,799 Pacific Aluminium 115 109 91 149 196 193 1,156 1,016 1,044 2,278 2,173 2,276 Inter-segment and other - 5 1 (1 ) 6 25 789 772 171 180 222 231 Integrated operations 1,881 1,436 916 1,122 1,199 1,250 16,446 16,346 15,782 13,640 13,345 14,037 Other product group items (f) (508 ) - - - - - - - - - - - Total Aluminium 1,373 1,436 916 1,122 1,199 1,250 16,446 16,346 15,782 13,640 13,345 14,037 Copper & Diamonds Rio Tinto Kennecott 100.0 318 249 333 427 422 530 1,864 1,936 2,189 1,993 1,734 1,638 Escondida 30.0 302 248 517 518 507 364 3,057 3,369 3,565 1,087 1,079 1,230 Grasberg joint venture (g) 171 138 174 30 42 89 - 1,137 1,151 1,615 1,642 2,859 Oyu Tolgoi and Turquoise Hill (h) 1,284 901 322 219 344 450 6,072 4,725 3,804 2,863 2,835 2,728 Diamonds (i) 64 85 97 118 132 164 267 441 655 967 922 907 Product group operations 2,139 1,621 1,443 1,312 1,447 1,597 11,260 11,608 11,364 8,525 8,212 9,362 Evaluation projects/other 11 1 (2 ) 5 5 4 129 135 166 146 142 127 Total Copper & Diamonds 2,150 1,622 1,441 1,317 1,452 1,601 11,389 11,743 11,530 8,671 8,354 9,489 Energy & Minerals Rio Tinto Coal Australia (j)/(q) 32 84 (107 ) 34 152 297 (837 ) 1,040 1,807 1,005 1,924 3,049 Iron Ore Company of Canada 58.7 189 202 75 154 157 151 975 988 1,018 2,397 2,382 2,308 Rio Tinto Iron & Titanium (k) 169 119 97 201 219 189 3,390 3,881 3,662 4,058 4,048 4,094 Rio Tinto Borates 100.0 44 28 31 62 65 53 518 523 508 980 936 984 Dampier Salt 68.4 14 13 11 20 22 23 165 150 146 239 232 317 Uranium (l) 8 21 30 4 37 25 (406 ) (327 ) (143 ) 1,324 1,307 1,303 Product group operations 456 467 137 475 652 738 3,805 6,255 6,998 10,003 10,829 12,055 Simandou iron ore project (m) - - - - - - 15 17 13 70 10 635 Evaluation projects/other - - 4 - - 1 41 41 38 33 25 763 Total Energy & Minerals 456 467 141 475 652 739 3,861 6,313 7,049 10,106 10,864 13,453 Other operations (n) 12 (35 ) (11 ) 26 32 34 (442 ) (328 ) 203 187 203 249 Product group total 5,279 4,691 3,355 4,622 4,980 5,269 45,742 50,611 50,923 43,026 42,925 47,652 Inter-segment transactions 129 206 142 Net assets/(liabilities) of disposal groups held for sale (r) 440 370 (7 ) Other items 65 70 (46 ) 43 42 51 (2,880 ) (2,631 ) (2,181 ) 4,432 3,882 3,377 Less: equity accounted units (500 ) (417 ) (651 ) (650 ) (647 ) (526 ) - - - - - - Total 4,844 4,344 2,658 4,015 4,375 4,794 43,431 48,556 48,877 47,458 46,807 51,029 Add back: Proceeds from disposal of property, plant and equipment 586 138 354 Total capital expenditure per cash flow statement 5,430 4,482 3,012 Less: Net cash/(debt) 255 (3,845 ) (9,587 ) Less: EAU funded balances excluded from net debt - - - Equity attributable to owners of Rio Tinto 43,686 44,711 39,290 Business units are classified according to the Group’s management structure. a) Gross sales revenue includes the sales revenue of equity accounted units on a proportionately consolidated basis (after adjusting for sales to subsidiaries) in addition to consolidated sales. Consolidated sales revenue includes subsidiary sales to equity accounted units which are not included in gross sales revenue. b) EBITDA of subsidiaries and the Group's share of EBITDA relating to equity accounted units represents profit before: tax, net finance items, depreciation and amortisation charged to the income statement in the period. Underlying EBITDA excludes the EBITDA impact of the same items that are excluded from underlying earnings. c) Represents profit after tax for the period attributable to the owners of the Rio Tinto Group. Business unit earnings are stated before finance items but after the amortisation of discount related to provisions. Earnings attributed to business units do not include amounts that are excluded in arriving at underlying earnings. d) Pilbara represents the Group’s 100% holding in Hamersley, 50% holding of Hope Downs Joint Venture and 65% holding of Robe River Iron Associates. The Group’s net beneficial interest in Robe River Iron Associates is 53%, as 30% is held through a 60% owned subsidiary and 35% is held through a 100% owned subsidiary. e) Presented on an integrated operations basis, splitting activities between Bauxite & Alumina, Primary Metal, Pacific Aluminium and Other integrated operations (which reflect the results of the integrated production of aluminium) and other product group items which relate to other commercial activities. f) Aluminium capital expenditure is reported net of US$508 million proceeds received on the sale of surplus land at Kitimat. These proceeds are not included in Aluminium’s free cash flow and the associated gain is excluded from business unit earnings and EBITDA. g) Through a joint venture agreement with Freeport-McMoRan Inc. (Freeport), we were entitled to 40% of material mined above an agreed threshold as a consequence of expansions and developments of the Grasberg facilities since 1998 (until 21 December 2018). On 28 September 2018, we entered into a binding agreement to sell our entire interest in the Grasberg mine to PT Indonesia Asahan Aluminium (Persero) (Inalum). The sale completed on 21 December 2018. h) Our interest in Oyu Tolgoi is held indirectly through our 50.8% investment in Turquoise Hill Resources Ltd (TRQ), where TRQ’s principal asset is its 66% investment in Oyu Tolgoi LLC, which owns the Oyu Tolgoi copper-gold mine. i) Includes our interests in Argyle (100%) and Diavik (60%). j) Includes our 82% interest in the Hail Creek coal mine (until 1 August 2018), our 80% interest in the Kestrel underground coal mine (until 1 August 2018) and interests in the Winchester South (until 1 June 2018) and Valeria development projects (until 1 August 2018). On 1 June 2018, we sold our entire 75% interest in the Winchester South coal development project in Queensland, Australia, to Whitehaven Coal Limited for US$200 million. On 1 August 2018, we sold our entire 82% interest in the Hail Creek coal mine and 71.2% interest in the Valeria coal development project in Queensland, Australia, to Glencore for US$1.7 billion. On 1 August 2018, we sold our entire 80% interest in the Kestrel underground coal mine in Queensland, Australia, to a consortium comprising private equity manager EMR Capital (EMR) and PT Adaro Energy Tbk (Adaro), an Indonesian listed coal company, for US$2.25 billion. On 1 September 2017, we sold our 100% shareholding in Coal & Allied Industries Limited to Yancoal Australia Limited for US$2.69 billion (before working capital adjustments). Rio Tinto Coal Australia’s operating assets of US$(837) million at 31 December 2018 include provisions for onerous contracts in relation to rail infrastructure capacity and capital gains tax payable on the divestments announced in the year, partly offset by financial assets and receivables relating to contingent royalties and disposal proceeds. k) Includes our interests in Rio Tinto Fer et Titane (100%), QIT Madagascar Minerals (QMM, 80%) and Richards Bay Minerals (attributable interest of 74%). l) Includes our interests in Energy Resources of Australia (68.4%) and Rössing Uranium Limited (Rössing) (68.6%). On 26 November 2018, we entered into a binding agreement with China National Uranium Corporation Limited (CNUC) to sell our entire 68.6% interest in the Rössing mine in Namibia, subject to certain conditions. m) Simfer Jersey Limited, a company incorporated in Jersey in which the Group has a 53% interest, has an 85% interest in Simfer S.A., the company that manages the Simandou project in Guinea. The Group therefore has a 45.05% indirect interest in Simfer S.A. These entities are consolidated as subsidiaries and together referred to as the Simandou iron ore project. n) Other operations include our 100% interest in the curtailed Gove alumina refinery and Rio Tinto Marine. o ) Capital expenditure is the net cash outflow on purchases less sales of property, plant and equipment, capitalised evaluation costs and purchases less sales of other intangible assets. The details provided include 100% of subsidiaries’ capital expenditure and Rio Tinto’s share of the capital expenditure of joint operations and equity accounted units. p) Operating assets of subsidiaries is comprised of net assets excluding post-retirement assets and liabilities, net of tax, and before deducting net debt. Operating assets are stated after the deduction of non-controlling interests – these are calculated by reference to the net assets of the relevant companies (ie inclusive of such companies’ debt and amounts due to or from Rio Tinto Group companies). q) Capital expenditure in 2016 for Rio Tinto Coal Australia includes net proceeds of US$192 million for the sale of our 100% interest in the Mount Pleasant thermal coal project to MACH Energy Australia Pty Ltd on 5 August 2016. r) Assets and liabilities held for sale at 31 December 2018 include our interest in Rössing Uranium Limited, the ISAL smelter, the Aluchemie anode plant, and the Alufluor aluminium fluoride plant. Assets and liabilities held for sale at 31 December 2017 included our interest in the Dunkerque aluminium smelter and certain other separate assets.

Principal accounting policies -

Principal accounting policies - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)Operation	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Disclosure of initial application of standards or interpretations [Line Items]
Retained earnings	$ 27,025,000,000	$ 23,761,000,000
Weighted average incremental borrowing rate applied to lease liabilities	4.70%
Undiscounted non-cancellable operating lease commitments	$ 1,717,000,000	1,845,000,000
Non-cancellable operating lease commitments	500,000
Non-cancellable operating lease commitments not expected to be charged against EBITDA	300,000
Operating lease expenses	$ 787,000,000	555,000,000	$ 541,000,000
Cash-generating units assessed for impairment	0
Depreciation or amortisation charges	$ 4,015,000,000	4,375,000,000	$ 4,794,000,000
Onerous contracts provision	$ 324,000,000
Operations with remaining lives	10 years
Number of operations | Operation	13
Decreasing provision	$ 800,000,000
Provision for carrying value close-down, restoration and environmental	$ 9,975,000,000	$ 9,983,000,000
Risk free rate decrease	0.50%
Risk free interest rate on provisions	2.00%
Intragroup loans	$ 14,000,000,000
Intangible assets [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Depreciation or amortisation charges	$ 0
Bottom of range [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Percent of certainty	50.00%
Assessment period of market prices	three years
Term of impairment review is under taken in relevant functional currency	five years
Risk free interest rate on provisions	0.50%
Top of range [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Percent of certainty	90.00%
Assessment period of market prices	five years
IFRS 16 [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Increase in lease liabilities (debt)	$ 1,200,000,000
Increase in right of use assets/net investments in leases	1,100,000,000
Net adjustments to other assets and liabilities	100,000,000
Retained earnings	100,000,000
Lease liability	1,300,000,000
IAS 17 [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Undiscounted non-cancellable operating lease commitments	1,700,000,000
IAS 17 [Member] | Entering into significant commitments or contingent liabilities
Disclosure of initial application of standards or interpretations [Line Items]
Undiscounted non-cancellable operating lease commitments	$ 1,700,000,000

Principal accounting policies_3

Principal accounting policies - Summary of significant differences between lease commitments and lease liability recorded on transition (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of initial application of standards or interpretations [Line Items]
Operating lease commitments under IAS 17 per note 31	$ 1,717	$ 1,845
Leases expiring in 12 months or fewer (a)	(100)
Committed leases not commenced (a)	(100)
Components excluded from the lease liability (a)	(200)
Cost of reasonably certain extensions (a)	300
Other (b)	100
Sub total	1,700
Effect of discounting on payments included in the calculation of the lease liability (excluding finance lease balances)	(400)
IAS 17 [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Operating lease commitments under IAS 17 per note 31	1,700
IFRS 16 [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Lease liability opening balance reported as at 1 January 2019 (IFRS 16)	$ 1,300

Operating segments - Addition_3

Operating segments - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Description of factors used to identify entity's reportable segments	Rio Tinto’s management structure is based on the principal product groups in the tables below together with the global functions that support the business, which include Growth & Innovation.
Description of types of products and services from which each reportable segment derives its revenues	Generally, business units are allocated to product groups based on their primary product. The Energy & Minerals product group includes businesses with products such as uranium, borates, salt and titanium dioxide feedstock together with coal operations (prior to the divestment of these assets), Iron Ore Company of Canada and the Simandou iron ore project, which is the responsibility of the Energy & Minerals product group chief executive. The Copper & Diamonds product group also produces gold, silver, molybdenum and other by-products.
Underlying profits of equity accounted units	$ 513	$ 339	$ 321
Subsidiaries [Member]
Disclosure of operating segments [Line Items]
Share of sales revenue of equity accounted units	$ 41	22	30
Percentage of capital expenditure	100.00%
Percentage of depreciation and amortisation	100.00%
Gross sales revenue [Member]
Disclosure of operating segments [Line Items]
Share of sales revenue of equity accounted units	$ 2,354	1,859	1,585
Underlying earnings [member]
Disclosure of operating segments [Line Items]
Underlying profits of equity accounted units	513	332	309
Underlying earnings [member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Underlying profits of equity accounted units	476	295	272
Underlying earnings [member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Underlying profits of equity accounted units	$ 38	$ 37	$ 37

Operating segments - Summary of

Operating segments - Summary of gross sales revenue within the reportable segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Consolidated sales revenue	$ 40,522	$ 40,030	$ 33,781
Reportable segments [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	42,850	41,872	35,329
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	18,485	18,251	14,605
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	12,191	11,005	9,458
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	6,468	4,842	4,524
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	5,697	7,764	6,734
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	9	10	8
Inter-segment transactions [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	(15)	(15)	(11)
Product group [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	42,835	41,857	35,318
Items excluded from underlying earnings [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		10	18
Gross sales revenue [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue	42,835	41,867	35,336
Share of equity accounted units and adjustments [Member]
Disclosure of operating segments [Line Items]
Sales revenue	$ (2,313)	$ (1,837)	$ (1,555)

Operating segments - Summary _2

Operating segments - Summary of capital expenditure within the reportable segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Capital expenditure	$ 4,844	$ 4,344	$ 2,658
Sales of property, plant and equipment and intangible assets	586	138	354
Capital expenditure per cash flow statement	5,430	4,482	3,012
Reportable segments [Member]
Disclosure of operating segments [Line Items]
Capital expenditure	5,279	4,691	3,355
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Capital expenditure	1,288	1,201	868
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Capital expenditure	1,373	1,436	916
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Capital expenditure	2,150	1,622	1,441
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Capital expenditure	456	467	141
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Capital expenditure	12	(35)	(11)
Other items [Member]
Disclosure of operating segments [Line Items]
Capital expenditure	65	70	(46)
Capital expenditure of equity accounted units
Disclosure of operating segments [Line Items]
Capital expenditure	$ (500)	$ (417)	$ (651)

Operating segments - Summary _3

Operating segments - Summary of depreciation and amortisation within the reportable segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	$ 4,015	$ 4,375	$ 4,794
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	1,682	1,645	1,645
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	1,122	1,199	1,250
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	1,317	1,452	1,601
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	475	652	739
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	26	32	34
Product group [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	4,622	4,980	5,269
Other items [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	43	42	51
Depreciation and amortisation of equity accounted units [Member]
Disclosure of operating segments [Line Items]
Depreciation and amortisation expense proportionately consolidated	$ (650)	$ (647)	$ (526)

Operating segments - Summary _4

Operating segments - Summary of tax charge within the reportable segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Tax charge	$ 4,242	$ 3,965	$ 1,567
Reportable segments [Member]
Disclosure of operating segments [Line Items]
Tax charge	3,929	4,030	2,114
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Tax charge	2,819	2,871	2,005
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Tax charge	532	543	171
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Tax charge	118	48	(320)
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Tax charge	511	652	331
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Tax charge	(51)	(84)	(73)
Other items [Member]
Disclosure of operating segments [Line Items]
Tax charge	(276)	(261)	(191)
Exploration and evaluation not attributed to product groups [Member]
Disclosure of operating segments [Line Items]
Tax charge	(38)	(36)	(27)
Finance costs [Member]
Disclosure of operating segments [Line Items]
Tax charge	(174)	(364)	(484)
Underlying earnings [member]
Disclosure of operating segments [Line Items]
Tax charge	3,441	3,369	1,412
Tax charge excluded from underlying earnings [Member]
Disclosure of operating segments [Line Items]
Tax charge	$ 801	$ 596	$ 155

Operating segments - Summary _5

Operating segments - Summary of Underlying EBITDA (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Underlying EBITDA	$ 18,136	$ 18,580	$ 13,510
Items excluded from underlying EBITDA	5,127	1,912	(687)
EBITDA	23,263	20,492	12,823
Depreciation, amortisation and impairment charges in subsidiaries and equity accounted units	(4,691)	(5,746)	(5,466)
Taxation and finance items in equity accounted units	(372)	(272)	(241)
Profit on ordinary activities before finance items and tax	18,200	14,474	7,116
Reportable segments [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	19,319	19,534	14,096
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	11,325	11,520	8,526
Profit on ordinary activities before finance items and tax	11,325	11,520	8,526
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	3,095	3,423	2,472
Profit on ordinary activities before finance items and tax	3,095	3,423	2,472
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	2,776	1,904	1,387
Profit on ordinary activities before finance items and tax	2,776	1,904	1,387
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	2,193	2,803	1,806
Profit on ordinary activities before finance items and tax	2,193	2,803	1,806
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	(70)	(116)	(95)
Profit on ordinary activities before finance items and tax	(70)	(116)	(95)
Central Pension Costs, Share-Based Payments & Insurance [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	(128)	(68)	(34)
Restructuring, Project and One-Off Costs [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	(272)	(177)	(13)
Profit on ordinary activities before finance items and tax	(272)	(177)	(13)
Exploration and evaluation not attributed to product groups [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	(231)	(218)	(175)
Central Costs [Member]
Disclosure of operating segments [Line Items]
Underlying EBITDA	(552)	(491)	(364)
Profit on ordinary activities before finance items and tax	$ (552)	$ (491)	$ (364)

Operating segments - Summary _6

Operating segments - Summary of underlying earnings within the reportable segments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Underlying earnings	$ 8,808	$ 8,627	$ 5,100
– attributable to owners of Rio Tinto (net earnings)	13,638	8,762	4,617
Items excluded from underlying earnings	4,830	135	(483)
Reportable segments [Member]
Disclosure of operating segments [Line Items]
Underlying earnings	9,825	9,642	6,064
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Underlying earnings	6,514	6,692	4,611
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Underlying earnings	1,347	1,583	947
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Underlying earnings	1,054	263	(18)
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Underlying earnings	1,012	1,242	612
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Underlying earnings	(102)	(138)	(88)
Central Pension Costs, Share-Based Payments & Insurance [Member]
Disclosure of operating segments [Line Items]
– attributable to owners of Rio Tinto (net earnings)	(90)	(48)	(24)
Restructuring, Project and One-Off Costs [Member]
Disclosure of operating segments [Line Items]
– attributable to owners of Rio Tinto (net earnings)	(190)	(124)	(9)
Exploration and evaluation not attributed to product groups [Member]
Disclosure of operating segments [Line Items]
– attributable to owners of Rio Tinto (net earnings)	(193)	(178)	(147)
Central Costs [Member]
Disclosure of operating segments [Line Items]
– attributable to owners of Rio Tinto (net earnings)	(410)	(311)	(208)
Finance costs [Member]
Disclosure of operating segments [Line Items]
– attributable to owners of Rio Tinto (net earnings)	(134)	(354)	(576)
Underlying earnings [member]
Disclosure of operating segments [Line Items]
– attributable to owners of Rio Tinto (net earnings)	$ 8,808	$ 8,627	$ 5,100

Operating segments - Reconcilia

Operating segments - Reconciliation of net earnings/(losses) to underlying earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Reconciliation Of Net Earnings Losses To Underlying Earnings [Abstract]
Impairment charges, Pre-tax	$ (132)
Net gains on consolidation and disposal of interests in businesses, Pre-tax	4,622
Exchange and derivative gains/(losses), Pre-tax
– Exchange (losses)/gains on external US dollar net debt and intragroup balances and derivatives, Pre-tax	694
Gain/(losses) on currency and interest rate derivatives not qualifying for hedge accounting, Pre-tax	(59)
(Losses)/gains on embedded commodity derivatives not qualifying for hedge accounting, Pre-tax	288
Losses from increases to closure estimates (non-operating and fully impaired sites), Pre-tax	(376)
Gain relating to surplus land at Kitimat, Pre-tax	602
Total excluded from underlying earnings, Pre-tax	5,639
Net earnings, Pre-tax	18,167	$ 12,816	$ 6,343
Underlying earnings, Pre-tax	12,528
Impairment charges, Tax	25
Net gains on consolidation and disposal of interests in businesses, Tax	(626)
– Exchange (losses)/gains on external US dollar net debt and intragroup balances and derivatives, Tax	(136)
- Gain/(losses) on currency and interest rate derivatives not qualifying for hedge accounting, Tax	11
- (Losses)/gains on embedded commodity derivatives not qualifying for hedge accounting, Tax	(83)
Losses from increases to closure estimates (non-operating and fully impaired sites), Tax	41
Gain relating to surplus land at Kitimat, Tax	(33)
Tax provision			(380)
Tax charge relating to expected divestments, Tax		(202)
Total excluded from underlying earnings, Tax	(801)
Taxation	(4,242)	(3,965)	(1,567)
Underlying earnings, Tax	(3,441)
Impairment charges, Non-controlling interests	3
Exchange and derivative gains/(losses, Non-controlling interests
– Exchange (losses)/gains on external US dollar net debt and intragroup balances and drivatives, Non-controlling interests	(8)
Total excluded from underlying earnings, Non-controlling interests	(8)
Net earnings, Non-controlling interests	(287)	(89)	(159)
Underlying earnings, Non-controlling interests	(279)
Impairment charges, Net	(104)	(481)	(183)
Net gains on consolidation and disposal of interests in businesses, Net	3,996	2,022	382
Exchange and derivative gains/(losses), Net
– Exchange (losses)/gains on external US dollar net debt and intragroup balances and derivatives, Net	550	(488)	516
- Gain/(losses) on currency and interest rate derivatives not qualifying for hedge accounting, Net	(48)	30	(12)
- (Losses)/gains on embedded commodity derivatives not qualifying for hedge accounting, Net	202	(352)	32
Losses from increases to closure estimates (non-operating and fully impaired sites), Net	(335)		(282)
Gain relating to surplus land at Kitimat, Net	569
Changes in corporate tax rates in the US and France, Net		(439)
Onerous port and rail contracts, Net			(329)
Restructuring costs and global headcount reductions, Net			(177)
Rio Tinto Kennecott insurance settlement, Net		45
Tax charge relating to expected divestments, Net		(202)
Other exclusions, Net			(50)
Total excluded from underlying earnings, Net	4,830	135	(483)
– attributable to owners of Rio Tinto (net earnings)	13,638	8,762	4,617
Underlying earnings, Net	$ 8,808	$ 8,627	$ 5,100

Operating segments - Reconcil_2

Operating segments - Reconciliation of net earnings/(losses) to underlying earnings (Parenthetical) (Detail) $ in Millions	Dec. 21, 2018USD ($)	Dec. 14, 2018USD ($)	Dec. 06, 2018USD ($)	Dec. 06, 2018AUD ($)	Aug. 01, 2018USD ($)	May 10, 2018USD ($)	Nov. 30, 2018USD ($)	Aug. 01, 2018	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Disclosure of operating segments [Line Items]
Net earnings, Pre-tax									$ 18,167,000,000	$ 12,816,000,000	$ 6,343,000,000
(Loss)/profit after tax									13,925,000,000	8,851,000,000	4,776,000,000
Post-tax foreign exchange gains									936,000,000
Post-tax foreign exchange loss									386,000,000
Impairment loss excluded from underlying earnings									134,000,000
Reversal of impairment loss			$ 242,000,000
Pre-tax gains on disposals of property, plant and equipment							$ 549,000,000		586,000,000	138,000,000	$ 354,000,000
Other income							53,000,000
Total impact							$ 569,000,000
Discount rate used in net present value of expected future cash flows for the port and rail capacity											2.00%
Post-tax onerous contract charge											$ 329,000,000
Underlying earnings [member]
Disclosure of operating segments [Line Items]
(Loss)/profit after tax									93,000,000
Increased closure provision				$ 296
US Dollar Net Debt [Member]
Disclosure of operating segments [Line Items]
Post-tax foreign exchange gains										420,000,000	123,000,000
Intragroup balances [Member]
Disclosure of operating segments [Line Items]
Post-tax foreign exchange gains											$ 393,000,000
Post-tax foreign exchange loss										908,000,000
Carbone savoie [Member] | Disposal of subsidiaries [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary											100.00%
Energy Resources of Australia Limited [Member]
Disclosure of operating segments [Line Items]
(Loss)/profit after tax									$ (241,000,000)	$ (29,000,000)
Ownership percentage in subsidiary			68.00%	68.00%
Elysis
Disclosure of operating segments [Line Items]
Pre-tax gain on consolidation						$ 171,000,000
Post-tax gain on consolidation						$ 141,000,000
Hail Creek [Member]
Disclosure of operating segments [Line Items]
Net earnings, Pre-tax					$ 1,141,000,000
(Loss)/profit after tax					836,000,000
Percentage of ownership interest exchanged in joint venture								82.00%
Kestrel Underground Coal Mine [Member]
Disclosure of operating segments [Line Items]
Net earnings, Pre-tax					1,010,000,000
(Loss)/profit after tax					$ 724,000,000
Percentage of ownership interest exchanged in joint venture								80.00%
Dunkerque Aluminium Smelter [Member]
Disclosure of operating segments [Line Items]
Net earnings, Pre-tax		$ 128,000,000
(Loss)/profit after tax		$ 122,000,000
Grasberg expansion [member]
Disclosure of operating segments [Line Items]
Net earnings, Pre-tax	$ 2,146,000,000
Tax payable	$ 0
Bengalla joint venture [Member] | Disposal of joint ventures [Member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture											40.00%

Operating segments - addition_4

Operating segments - additional information - Consolidated sales revenue by destination (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	100.00%	100.00%	100.00%
Consolidated sales revenue	$ 40,522	$ 40,030	$ 33,781
China [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	44.60%	44.20%	43.60%
Consolidated sales revenue	$ 18,061	$ 17,706	$ 14,742
Asia (excluding China and Japan) [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	11.50%	12.80%	13.90%
Consolidated sales revenue	$ 4,665	$ 5,108	$ 4,692
United States [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	15.50%	14.30%	13.90%
Consolidated sales revenue	$ 6,278	$ 5,716	$ 4,709
Japan [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	9.60%	11.70%	11.30%
Consolidated sales revenue	$ 3,873	$ 4,701	$ 3,809
Europe (excluding UK) [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	9.10%	7.50%	7.60%
Consolidated sales revenue	$ 3,706	$ 3,015	$ 2,579
Canada [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	3.20%	2.80%	3.00%
Consolidated sales revenue	$ 1,340	$ 1,111	$ 1,024
Australia [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	1.80%	1.80%	2.00%
Consolidated sales revenue	$ 720	$ 710	$ 675
United Kingdom [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	1.00%	1.10%	1.20%
Consolidated sales revenue	$ 386	$ 449	$ 391
Other countries [Member]
Disclosure Of Geographical Areas [Line Items]
Percentage of consolidated sales revenue	3.70%	3.80%	3.50%
Consolidated sales revenue	$ 1,493	$ 1,514	$ 1,160

Operating segments - addition_5

Operating segments - additional information - Consolidated sales revenue by product (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	$ 40,594
Other revenue	(72)
Consolidated sales revenue	40,522	$ 40,030	$ 33,781
Share of equity accounted units and adjustments [Member]
Disclosure Of Products And Services [Line Items]
Consolidated sales revenue	2,313	1,837	1,555
Gross sales revenue [Member]
Disclosure Of Products And Services [Line Items]
Consolidated sales revenue	42,835	41,867	35,336
Iron Ore [Member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	19,888
Other revenue	(21)
Consolidated sales revenue	19,867	20,010	15,855
Aluminium [Member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	12,041
Other revenue	(22)
Consolidated sales revenue	12,019	10,864	9,342
Copper [member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	2,420
Other revenue	(32)
Consolidated sales revenue	2,388	1,760	1,609
Coal [member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	986
Other revenue	3
Consolidated sales revenue	989	2,822	2,567
Industrial minerals [member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	2,093
Consolidated sales revenue	2,093	2,060	1,954
Gold [member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	869
Consolidated sales revenue	869	378	608
Diamonds [member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	695
Consolidated sales revenue	695	706	613
Other Product [Member]
Disclosure Of Products And Services [Line Items]
Revenue from contracts with customers	1,602
Consolidated sales revenue	$ 1,602	$ 1,430	$ 1,233

Operating segments - addition_6

Operating segments - additional information - Summary of non-current assets other than excluded items (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	$ 64,655	$ 71,063
Deferred tax assets	3,137	3,395
Other financial assets (including loans to equity accounted units)	814	510
Tax recoverable	8	30
Trade and other receivables	1,304	1,397
Total non-current assets	70,047	76,554
Quasi equity loans [member]
Disclosure Of Geographical Areas [Line Items]
Quasi equity loans to equity accounted units	129	159
Australia [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	28,592	32,890
Deferred tax assets	796	1,055
Canada [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	13,775	14,822
Deferred tax assets	545	546
Mongolia [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	9,912	8,582
Deferred tax assets	703	631
United States [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	4,815	4,812
Deferred tax assets	932	877
Africa [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	3,476	3,781
South America [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	3,047	3,304
Indonesia [member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items		1,458
Europe excluding France and the UK [member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	50	362
United Kingdom [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	59	66
France [member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	79	94
Other countries [Member]
Disclosure Of Geographical Areas [Line Items]
Non-current assets other than excluded items	850	892
Deferred tax assets	$ 161	$ 286

Operating segments - addition_7

Operating segments - additional information - Summary of non-current assets other than excluded items (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Quasi equity loans [member]
Disclosure Of Geographical Areas [Line Items]
Quasi equity loans to equity accounted units	$ 129	$ 159
Non-quasi equity loan [member]
Disclosure Of Geographical Areas [Line Items]
Investments in equity accounted units	38	39
Non-current assets [member]
Disclosure Of Geographical Areas [Line Items]
Investments in equity accounted units	4,170	$ 4,327
France [member]
Disclosure Of Geographical Areas [Line Items]
Change in non-current assets other than excluded items	$ 182

Net operating costs (excludin_3

Net operating costs (excluding items shown separately) - Summary of net operating costs (excluding items shown separately) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Expense By Nature [Abstract]
Raw materials, consumables, repairs and maintenance	$ 10,613	$ 9,286	$ 8,760
Amortisation of intangible assets	133	177	227
Depreciation of property, plant and equipment	3,882	4,198	4,567
Employment costs	4,728	4,765	4,881
Shipping and other freight costs	2,580	2,338	1,454
(Increase)/decrease in finished goods and work in progress	(186)	(82)	87
Royalties	2,117	2,228	1,889
Amounts charged by equity accounted units	1,200	980	1,184
Net foreign exchange (gains)/losses	(56)	61	38
Other external costs	3,184	3,967	3,512
Gain on sale of property, plant and equipment	(506)	(32)	(40)
Provisions (including exchange differences on provisions)	1,011	527	1,404
Research and development	45	58	60
Costs included above qualifying for capitalisation	(589)	(486)	(521)
Other operating income	(1,041)	(1,002)	(703)
Net operating costs (excluding items shown separately)	$ 27,115	$ 26,983	$ 26,799

Net operating costs (excludin_4

Net operating costs (excluding items shown separately) - Summary of net operating costs (excluding items shown separately) (Parenthetical) (Detail) £ in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2017GBP (£)	Dec. 31, 2016USD ($)
Disclosure Of Operating Costs [Line Items]
Operating lease expenses		$ 787	$ 555		$ 541
Purchases of the other investors' share of production		332	229		383
Pre-tax gains on disposals of property, plant and equipment	$ 549	586	138		$ 354
United Kingdoms Financial Conduct Authority (FCA) [Member]
Disclosure Of Operating Costs [Line Items]
Financial penalty			$ 36.4	£ 27.4
Kitimat [Member]
Disclosure Of Operating Costs [Line Items]
Pre-tax gains on disposals of property, plant and equipment		$ 549

Employment costs - Summary of e

Employment costs - Summary of employment costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Total employment costs
– Wages and salaries	$ 4,154	$ 4,129	$ 4,235
– Social security costs	336	337	429
– Net post-retirement charge	532	500	522
– Share-based payment charge	122	91	116
Total employment costs	4,728	4,765	4,881
Less: charged within provisions (a)	(416)	(292)	(421)
Employment costs before utilisation of provisions [Member]
Total employment costs
Total employment costs	$ 5,144	$ 5,057	$ 5,302

Impairment charges - Summary of

Impairment charges - Summary of impairment charges (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge	$ (132)	$ (796)	$ (249)
Total impairment charge net of reversals in the financial information by business unit	(132)	(796)	(249)
Taxation (including related to EAUs)	25	141	66
Non-controlling interests	3	174
Total impairment in the income statement	(104)	(481)	(183)
Impairment charges, Tax	25
Impairment charges, Non-controlling interests	3
Impairment charge, net amount	(104)
Intangible assets [Member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge	(2)	(357)	(1)
Property, plant and equipment [member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge	(130)	(435)	(248)
Other assets and liabilities [member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge		(4)
Aluminium [Member] | ISAL Smelter [member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge	(123)
Impairment charges, Tax	25
Impairment charge, net amount	(98)
Energy & Minerals [Member] | Roughrider [member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge		(357)
Energy & Minerals [Member] | Rossing [member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge	(9)	(267)
Impairment charges, Non-controlling interests	3
Impairment charge, net amount	$ (6)
Copper & Diamonds [member] | Argyle Diamond Mine [member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge		$ (172)	(241)
Other operations [Member]
Disclosure Of Impairment Loss Recognised Or Reversed [Line Items]
Pre-tax impairment charge			$ (8)

Impairment charges - Additional

Impairment charges - Additional information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge	$ 134,000,000
Deferred tax assets	3,137,000,000	$ 3,395,000,000
Pre-tax impairment charge net of reversals	$ 132,000,000	796,000,000	$ 249,000,000
Increase in discount rate	1.90%
Reduction of the copper price throughout the life of mine	$ 0.39
long term reduction in copper price	13.00%
Property, plant and equipment [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge net of reversals	$ 130,000,000	435,000,000	248,000,000
Australia [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Deferred tax assets	796,000,000	1,055,000,000
Canada [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Deferred tax assets	545,000,000	546,000,000
Mongolia [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Deferred tax assets	703,000,000	631,000,000
Mongolia [Member] | Copper & Diamonds [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Recoverable amount of asset or cash-generating unit	1,100,000,000	1,300,000,000
Pre-tax impairment charge net of reversals	$ 0
Net present value of post tax cash flows discounted percentage	8.00%
Carrying value from cash generating unit	$ 3,100,000,000
Assets and liabilities classified as held for sale [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Deferred tax assets	66,000,000	49,000,000
ISAL Smelter [member] | Assets and liabilities classified as held for sale [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Business acquisition binding offer amount	$ 345,000,000
ISAL Smelter [member] | Assets and liabilities classified as held for sale [member] | Aluminerie Alouette Inc | Netherlands [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Percentage of ownership interest to be sold	53.30%
ISAL Smelter [member] | Assets and liabilities classified as held for sale [member] | Alufluor Ab | Sweden [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Percentage of ownership interest to be sold	50.00%
Rossing [member] | Energy & Minerals [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge net of reversals	$ 9,000,000	267,000,000
Rossing [member] | Namibia [Member] | Energy & Minerals [Member] | Property, plant and equipment [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge		267,000,000
Rossing [member] | Namibia, Dollars | Energy & Minerals [Member] | Property, plant and equipment [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge	$ 9,000,000
Argyle Diamond Mine [member] | Copper & Diamonds [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge net of reversals		172,000,000	241,000,000
Argyle Diamond Mine [member] | Australia [Member] | Copper & Diamonds [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge		172,000,000
Description of impairment trigger assessment	In 2016, our annual impairment trigger assessment at the Argyle CGU identified the impact of lower production volumes compared with forecast and lower prices achieved for bulk diamonds as impairment indicators. We calculated a recoverable amount for Argyle of US$191 million, resulting in a pre-tax impairment charge of US$241 million to property, plant and equipment and intangible assets. In 2017, our annual impairment trigger assessment at the Argyle CGU identified impairment indicators because of lower production volumes compared with forecast, a smaller than expected contribution from productivity improvements and lower realised prices. In assessing the recoverable amount of the assets, we determined that the property, plant and equipment, including an updated closure asset, was fully impaired resulting in a pre-tax impairment charge of US$172 million. The impairment charge resulted in the recognition of deferred tax assets of US$34 million, which will be recovered by other business units in the same tax group.
Deferred tax assets		34,000,000
Recoverable amount of asset or cash-generating unit			191,000,000
Argyle Diamond Mine [member] | Australia [Member] | Copper & Diamonds [member] | Property, plant and equipment [member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge			$ 241,000,000
Roughrider [member] | Energy & Minerals [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge net of reversals		357,000,000
Roughrider [member] | Canada [Member] | Energy & Minerals [Member]
Disclosure Of Impairment Loss And Reversal Of Impairment Loss [Line Items]
Pre-tax impairment charge net of reversals		$ 357,000,000

Share of profit after tax of _3

Share of profit after tax of equity accounted units - Summary of share of profit after tax of equity accounted units (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Equity Accounted Units [Line Items]
Sales revenue: Rio Tinto share	$ 40,522	$ 40,030	$ 33,781
Operating costs	(27,115)	(26,983)	(26,799)
Finance items	(33)	(1,658)	(773)
Profit before taxation	18,167	12,816	6,343
Taxation	(4,242)	(3,965)	(1,567)
Rio Tinto [member]
Disclosure Of Equity Accounted Units [Line Items]
Sales revenue: Rio Tinto share	2,497	1,960	1,727
Operating costs	(1,656)	(1,400)	(1,237)
Profit before finance items and taxation	841	560	490
Finance items	(69)	(47)	(33)
Share of profit after tax of equity accounted units	14	17	20
Profit before taxation	786	530	477
Taxation	(273)	(191)	(156)
Profit for the year (Rio Tinto share)	$ 513	$ 339	$ 321

Finance income and finance co_3

Finance income and finance costs - Summary of finance income and finance costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Material Income And Expense [Abstract]
Finance income from equity accounted units (Rio Tinto share)	$ 7	$ 4	$ 6
Other finance income (including bank deposits and other financial assets)	242	137	83
Total finance income	249	141	89
Interest on:
– Financial liabilities at amortised cost and associated derivatives	(775)	(819)	(895)
– Finance leases	(2)	(3)	(3)
Fair value movements:
– Bonds designated as hedged items in fair value hedges	96	28	89
– Derivatives designated as hedging instruments in fair value hedges	(73)	(22)	(89)
Loss on early redemption of bonds	(94)	(256)	(324)
Amounts capitalised	296	224	111
Total finance costs	$ (552)	$ (848)	$ (1,111)

Finance income and finance co_4

Finance income and finance costs - Summary of finance income and finance costs (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Material Income And Expense [Abstract]
Premium charges for redemption of bonds	$ 72	$ 238	$ 441
Unamortized Debt Issuance Costs and Fees	9	14	42
Fair value hedge adjustment	16	$ 4	$ (159)
Reclassification of cost of hedging out of reserves	$ 3

Taxation - Summary of taxation

Taxation - Summary of taxation charge (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Major Components Of Tax Expense Income [Abstract]
– Current	$ 3,726	$ 3,270	$ 2,115
– Deferred	516	695	(548)
Total taxation charge	$ 4,242	$ 3,965	$ 1,567

Taxation - Summary of prima fac

Taxation - Summary of prima facie tax reconciliation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates [Abstract]
Profit before taxation	$ 18,167	$ 12,816	$ 6,343
Deduct: share of profit after tax of equity accounted units	(513)	(339)	(321)
Parent companies' and subsidiaries' profit before tax	17,654	12,477	6,022
Prima facie tax payable at UK rate of 19% (2017: 19%; 2016: 20%)	3,354	2,371	1,204
Higher rate of taxation on Australian underlying earnings	1,106	1,069	604
Impact of items excluded in arriving at underlying earnings
– Impairment charges		10	(16)
– Net gains and losses on consolidation and disposal of interests in businesses	(251)	(123)	30
– Exchange and gains/(losses) on derivatives	32	(48)	(33)
– Losses from increases to closure estimates (non-operating and fully impaired sites)	30		(40)
– Gain relating to surplus land at Kitimat	(81)
– Changes in corporate tax rates in the US and France		439
– Onerous port and rail contracts			(46)
– Tax provision			380
– Tax charge relating to expected divestments		202
– Other exclusions		14	(48)
Impact of changes in tax rates and laws	47	21	(9)
Other tax rates applicable outside the UK and Australia on underlying earnings	(47)	(92)	(283)
Resource depletion and other depreciation allowances	(46)	(33)	(15)
Recognition of previously unrecognised deferred tax assets		(40)	(154)
Write-down of previously recognised deferred tax assets	13	160
Other items	85	15	(7)
Total taxation charge	$ 4,242	$ 3,965	$ 1,567

Taxation - Summary of prima f_2

Taxation - Summary of prima facie tax reconciliation (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation Of Accounting Profit Multiplied By Applicable Tax Rates [Abstract]
UK tax payable (receivable) rate	19.00%	19.00%	20.00%
Groups share of profit of equity accounted units net of tax	$ 273	$ 191	$ 156

Taxation - Summary of tax relat

Taxation - Summary of tax relating to components of other comprehensive income or loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Relating To Components Of Other Comprehensive Income That Will Be Reclassified To Profit Or Loss [Abstract]
– Cash flow hedge fair value (gains)/losses	$ (54)	$ (1)	$ 4
Tax (charge)/credit on actuarial gains and losses on post-retirement benefit plans	(271)	(12)	29
Adjustments to deferred tax on post-retirement benefit plans due to changes in corporate tax rates in the US and France		(140)
Tax relating to components of other comprehensive income/(loss) for the year	$ (325)	$ (153)	$ 33

Taxation - Summary of tax rel_2

Taxation - Summary of tax relating to components of other comprehensive income or loss (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Relating To Components Of Other Comprehensive Income That Will Be Reclassified To Profit Or Loss [Abstract]
Deferred tax charge included in other comprehensive income	$ 325,000,000	$ 153,000,000	$ 33,000,000
Current tax charge included in other comprehensive income	$ 0	$ 0	$ 0

Earnings per ordinary share - S

Earnings per ordinary share - Summary of earnings (loss) per ordinary shares (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Basic earnings per share attributable to ordinary shareholders of Rio Tinto	$ 13,638	$ 8,762	$ 4,617
Diluted earnings per share attributable to ordinary shareholders of Rio Tinto	$ 13,638	$ 8,762	$ 4,617
Basic earnings per share attributable to ordinary shareholders of Rio Tinto, Weighted average number of shares	1,719.3	1,786.7	1,797.3
Diluted earnings per share attributable to ordinary shareholders of Rio Tinto, Weighted average number of shares	1,731.7	1,799.5	1,808.6
Basic earnings per share	$ 793.2	$ 490.4	$ 256.9
Diluted earnings per share	$ 787.6	$ 486.9	$ 255.3

Earnings per ordinary share -_2

Earnings per ordinary share - Summary of earnings (loss) per ordinary shares (Parenthetical) (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Line Items]
Weighted average number of shares outstanding	1,719.3	1,786.7	1,797.3
Effect of dilutive securities shares	12.4	12.8	11.3
Rio Tinto plc [member]
Earnings Per Share [Line Items]
Weighted average number of shares outstanding	1,312.7	1,364.5	1,373.7
Rio Tinto Limited [member]
Earnings Per Share [Line Items]
Weighted average number of shares outstanding	406.6	422.3	423.6

Dividends - Summary of dividend

Dividends - Summary of dividends paid (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Dividends [Line Items]
Dividends paid during the year	$ 5,356	$ 4,250	$ 2,725
Dividends per share: paid during the year	$ 3.07	$ 2.35	$ 1.525
Final Dividends [Member]
Disclosure of Dividends [Line Items]
Dividends per share: proposed in the announcement of the results for the year	1.80	$ 1.80	$ 1.25
Special Dividends [Member]
Disclosure of Dividends [Line Items]
Dividends per share: proposed in the announcement of the results for the year	$ 2.43
Rio Tinto plc [member]
Disclosure of Dividends [Line Items]
Previous year final dividend paid	$ 2,446	$ 1,725	$ 1,443
Interim dividend paid	1,666	1,530	604
Rio Tinto Limited [member]
Disclosure of Dividends [Line Items]
Previous year final dividend paid	731	523	473
Interim dividend paid	$ 513	$ 472	$ 205

Dividends - Summary of divide_2

Dividends - Summary of dividends per share (Detail)	12 Months Ended
	Dec. 31, 2018$ / shares	Dec. 31, 2018£ / shares	Dec. 31, 2018$ / shares	Dec. 31, 2017$ / shares	Dec. 31, 2017£ / shares	Dec. 31, 2017$ / shares	Dec. 31, 2016$ / shares	Dec. 31, 2016£ / shares	Dec. 31, 2016$ / shares	Dec. 31, 2015$ / shares
Disclosure of Dividends [Line Items]
Previous year final dividend per share				$ 1.8			$ 1.25			$ 1.075
Interim dividend per share	$ 1.27			$ 1.1			$ 0.45
Rio Tinto plc [member]
Disclosure of Dividends [Line Items]
Previous year final dividend per share | £ / shares		£ 1.2943			£ 1.0056			£ 0.7421
Interim dividend per share | £ / shares		£ 0.9682			£ 0.8313			£ 0.3380
Rio Tinto Limited [member]
Disclosure of Dividends [Line Items]
Previous year final dividend per share			$ 2.2853			$ 1.6362			$ 1.5189
Interim dividend per share			$ 1.7084			$ 1.3772			$ 0.5913

Dividends - Summary of divide_3

Dividends - Summary of dividends per share (Parenthetical) (Detail) - Rio Tinto Limited [member]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Dividends [Line Items]
Franked final dividend percentage	30.00%	30.00%	30.00%
Franked Interim dividend percentage	30.00%	30.00%	30.00%

Dividends - Summary of number o

Dividends - Summary of number of shares dividend distributed (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Rio Tinto plc [member]
Disclosure of Dividends [Line Items]
Previous year final dividend number of shares	1,334.8	1,374.6	1,373.9
Interim dividend number of shares	1,308.4	1,366.1	1,374.4
Rio Tinto Limited [member]
Disclosure of Dividends [Line Items]
Previous year final dividend number of shares	412.4	424	423.5
Interim dividend number of shares	412.4	424	424

Dividends - Additional informat

Dividends - Additional information (Detail) $ / shares in Units, $ in Millions	Mar. 01, 2019	Feb. 28, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2018£ / sharesshares	Dec. 31, 2018$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2017£ / sharesshares	Dec. 31, 2017$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2016£ / sharesshares	Dec. 31, 2016$ / sharesshares	Dec. 31, 2015$ / shares
Disclosure of Dividends [Line Items]
Final dividend per share | $ / shares						$ 1.8			$ 1.25			$ 1.075
Interim dividend per share | $ / shares			$ 1.27			$ 1.1			$ 0.45
Rio Tinto Limited shares were held by Rio Tinto plc | shares			0	0	0	0	0	0	0	0	0
Final Dividends [Member]
Disclosure of Dividends [Line Items]
Dividends per share: proposed in the announcement of the results for the year | $ / shares			$ 1.80			$ 1.80			$ 1.25
Special Dividends [Member]
Disclosure of Dividends [Line Items]
Dividends per share: proposed in the announcement of the results for the year | $ / shares			$ 2.43
Potential ordinary share transactions [Member]
Disclosure of Dividends [Line Items]
Dividends payment proposed in the announcement of the results for the year | $		$ 7,000
Dividends payment date	Apr. 18, 2019
Dividends record date	Mar. 8, 2019
Potential ordinary share transactions [Member] | Final Dividends [Member]
Disclosure of Dividends [Line Items]
Dividends per share: proposed in the announcement of the results for the year | $ / shares		$ 1.80
Potential ordinary share transactions [Member] | Special Dividends [Member]
Disclosure of Dividends [Line Items]
Dividends per share: proposed in the announcement of the results for the year | $ / shares		$ 2.43
Rio Tinto plc [member]
Disclosure of Dividends [Line Items]
Final dividend per share | £ / shares				£ 1.2943			£ 1.0056			£ 0.7421
Interim dividend per share | £ / shares				£ 0.9682			£ 0.8313			£ 0.3380
Rio Tinto plc [member] | Ordinary shares [Member]
Disclosure of Dividends [Line Items]
Number of share excluded from previous year final dividend calculation | shares			132,294	132,294	132,294	277,946	277,946	277,946	428,529	428,529	428,529
Number of share excluded from interim dividend calculation | shares			314,529	314,529	314,529	173,297	173,297	173,297	217,661	217,661	217,661
Rio Tinto plc [member] | American depository receipts [member]
Disclosure of Dividends [Line Items]
Number of share excluded from previous year final dividend calculation | shares			22,824	22,824	22,824	22,021	22,021	22,021	13,881	13,881	13,881
Number of share excluded from interim dividend calculation | shares			36,321	36,321	36,321	24,377	24,377	24,377	31,604	31,604	31,604
Rio Tinto Limited [member]
Disclosure of Dividends [Line Items]
Final dividend per share | $ / shares					$ 2.2853			$ 1.6362			$ 1.5189
Interim dividend per share | $ / shares					$ 1.7084			$ 1.3772			$ 0.5913
Number of share excluded from previous year final dividend calculation | shares			130,129	130,129	130,129	214,278	214,278	214,278	681,818	681,818	681,818
Number of share excluded from interim dividend calculation | shares			251,394	251,394	251,394	274,899	274,899	274,899	152,834	152,834	152,834
Rio Tinto Limited shares were held by Rio Tinto plc | shares			1,416,728	1,416,728	1,416,728
Retained profits and reserves distributed as dividends | $			$ 6,178			$ 8,542			$ 11,577

Goodwill - Summary of goodwill

Goodwill - Summary of goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill at beginning of period	$ 1,037	$ 951
Adjustment on currency translation	(125)	86
Goodwill at end of period	912	1,037
Cost [member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill at beginning of period	17,942	17,144
Goodwill at end of period	15,861	17,942
Accumulated impairment [Member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill at beginning of period	(16,905)	(16,193)
Goodwill at end of period	$ (14,949)	$ (16,905)

Goodwill - Summary of Allocated

Goodwill - Summary of Allocated goodwill (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill	$ 912	$ 1,037	$ 951
Richards Bay Minerals [member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill	474	552
Pilbara [member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill	351	389
Dampier Salt [member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Goodwill	$ 87	$ 96

Goodwill - Additional informati

Goodwill - Additional information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Richards Bay Minerals [member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Impairment charges	$ 0	$ 0
Fair value less costs of disposal, post-tax discount rate	8.80%	8.70%
Description of valuation techniques used to measure fair value less costs of disposal	The recoverable amount has been assessed by reference to FVLCD, in line with the policy set out in note 1(i) and classified as level 3 under the fair value hierarchy. FVLCD was determined by estimating cash flows until the end of the life-of-mine plan including anticipated expansions. In arriving at FVLCD, a post-tax discount rate of 8.8% (2017: 8.7%) has been applied to the post-tax cash flows expressed in real terms.
Description of level of fair value hierarchy within which fair value measurement is categorized	level 3
Description of basis on which recoverable amount determined	Other assumptions include the long-term pig iron and zircon prices and operating costs. Future selling prices and operating costs have been estimated in line with the policy set out in note 1(i). The recoverable amount of the CGU exceeds the carrying value when each of these sensitivities are applied whilst keeping all other assumptions constant.
Pilbara [member]
Disclosure of reconciliation of changes in goodwill [Line Items]
Fair value less costs of disposal, post-tax discount rate	6.80%	6.70%
Description of valuation techniques used to measure fair value less costs of disposal	The annual impairment review of the Pilbara CGU has been assessed by reference to FVLCD using discounted cash flows, which is in line with the policy set out in note 1(i) and is classified as level 3 under the fair value hierarchy. In arriving at FVLCD, a post-tax discount rate of 6.8% (2017: 6.7%) has been applied to the post-tax cash flows expressed in real terms. The recoverable amount was determined to be significantly in excess of carrying value, and there are no reasonably possible changes in key assumptions that would cause the remaining goodwill to be impaired.
Description of level of fair value hierarchy within which fair value measurement is categorized	level 3

Goodwill - Key assumptions calc

Goodwill - Key assumptions calculation of fair value less costs of disposal (Detail) - Richards Bay Minerals [member] $ in Millions	Dec. 31, 2018USD ($)
5% decrease in the titanium slag price [member]
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Corresponding decrease in FVLCD	$ 174
1% increase in the discount rate applied to post-tax cash flows [member]
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Corresponding decrease in FVLCD	195
10% strengthening of South African rand [member]
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Corresponding decrease in FVLCD	$ 328

Goodwill - Key assumptions ca_2

Goodwill - Key assumptions calculation of fair value less costs of disposal (Parenthetical) (Detail) - Richards Bay Minerals [member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Fair value less costs of disposal, post-tax discount rate	8.80%	8.70%
5% decrease in the titanium slag price [member] | Titanium [member]
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Percentage of decrease in the titanium slag price	5.00%
1% increase in the discount rate applied to post-tax cash flows [member]
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Fair value less costs of disposal, post-tax discount rate	1.00%
10% strengthening of South African rand [member]
Disclosure of key assumptions calculation of fair value less costs of disposal [Line Items]
Strengthening percentage of the South African rand	10.00%

Intangible assets - Summary of

Intangible assets - Summary of intangible assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	$ 3,119	$ 3,279
Adjustment on currency translation	(245)	216
Expenditure during the year	174	122
Amortisation for the year	(133)	(177)	$ (227)
Impairment charges	(2)	(357)
Disposals, transfers and other movements	(134)	36
Intangible assets at end of period	2,779	3,119	3,279
Cost [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	7,857
Intangible assets at end of period	7,215	7,857
Accumulated amortisation and impairment [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	(4,738)
Intangible assets at end of period	(4,436)	(4,738)
Exploration and evaluation [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	393	711
Adjustment on currency translation	(25)	27
Expenditure during the year	90	57
Impairment charges		(357)
Disposals, transfers and other movements	(225)	(45)
Intangible assets at end of period	233	393	711
Exploration and evaluation [member] | Cost [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	2,658
Intangible assets at end of period	2,346	2,658
Exploration and evaluation [member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	(2,265)
Intangible assets at end of period	(2,113)	(2,265)
Trademarks, patented and non-patented technology [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	75	78
Adjustment on currency translation	(3)	10
Expenditure during the year	1
Amortisation for the year	(14)	(13)
Intangible assets at end of period	59	75	78
Trademarks, patented and non-patented technology [member] | Cost [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	224
Intangible assets at end of period	217	224
Trademarks, patented and non-patented technology [member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	(149)
Intangible assets at end of period	(158)	(149)
Contract based intangible assets [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	2,188	2,103
Adjustment on currency translation	(171)	150
Amortisation for the year	(23)	(67)
Disposals, transfers and other movements	(12)	2
Intangible assets at end of period	1,982	2,188	2,103
Contract based intangible assets [member] | Cost [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	3,438
Intangible assets at end of period	3,114	3,438
Contract based intangible assets [member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	(1,250)
Intangible assets at end of period	(1,132)	(1,250)
Other intangible assets [Member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	463	387
Adjustment on currency translation	(46)	29
Expenditure during the year	83	65
Amortisation for the year	(96)	(97)
Impairment charges	(2)
Disposals, transfers and other movements	103	79
Intangible assets at end of period	505	463	$ 387
Other intangible assets [Member] | Cost [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	1,537
Intangible assets at end of period	1,538	1,537
Other intangible assets [Member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets at beginning of period	(1,074)
Intangible assets at end of period	$ (1,033)	$ (1,074)

Intangible assets - Summary o_2

Intangible assets - Summary of intangible assets (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets	$ 2,779	$ 3,119	$ 3,279
Disposals, transfers and other movements	$ (134)	$ 36
Quebec smelters [member]
Disclosure of detailed information about intangible assets [Line Items]
Fair value less costs of disposal, post-tax discount rate	6.80%	6.70%
Description of recoverable amount of asset is fair value less costs of disposal or value in use	the Quebec smelters CGU. The Quebec smelters CGU was tested for impairment by reference to FVLCD using discounted cash flows, which is in line with the policy set out in note 1(i). The recoverable amount of the Quebec smelters is classified as level 3 under the fair value hierarchy
Description of level of fair value hierarchy within which fair value measurement is categorized	level 3
Water rights [member] | Quebec smelters [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets	$ 1,684
Trademarks [member] | Bottom of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	14 years
Trademarks [member] | Top of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	20 years
Patented and non-patented technology [member] | Bottom of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	ten years
Patented and non-patented technology [member] | Top of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	20 years
Power contracts water rights [member] | Bottom of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	two years
Power contracts water rights [member] | Top of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	45 years
Other purchase and customer contracts [member] | Bottom of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	five years
Other purchase and customer contracts [member] | Top of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	15 years
Computer software [Member] | Bottom of range [Member] | Internally generated [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	two years
Computer software [Member] | Top of range [Member] | Internally generated [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	five years
Other intangible assets [Member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets	$ 505	$ 463	387
Disposals, transfers and other movements	$ 103	79
Other intangible assets [Member] | Bottom of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	two years
Other intangible assets [Member] | Top of range [Member]
Disclosure of detailed information about intangible assets [Line Items]
Finite life intangible assets, useful lives	20 years
Exploration and evaluation [member]
Disclosure of detailed information about intangible assets [Line Items]
Intangible assets	$ 233	393	$ 711
Disposals, transfers and other movements	$ (225)	(45)
Exploration and evaluation [member] | Kemano Tunnel Project [Member]
Disclosure of detailed information about intangible assets [Line Items]
Disposals, transfers and other movements		$ 34

Intangible assets - Summary o_3

Intangible assets - Summary of exploration and evaluation expenditure (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Exploration And Evaluation Expenditure [Abstract]
Net expenditure in the year (net of cash proceeds of US$233 million (2017: US$3 million; 2016: US$208 million) on disposal of undeveloped projects)	$ 345	$ 493	$ 284
Non-cash movements and non-cash proceeds on disposal of undeveloped projects	45	(24)	(177)
Amount capitalised during the year	90	57	8
Net charge for the year	(210)	(460)	(453)
Reconciliation to income statement
Exploration and evaluation costs	(488)	(445)	(497)
Profit/(loss) relating to interests in undeveloped projects	278	(15)	44
Net charge for the year	$ (210)	$ (460)	$ (453)

Intangible assets - Summary o_4

Intangible assets - Summary of exploration and evaluation expenditure (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about intangible assets [Line Items]
Net proceeds on disposal of undeveloped projects	$ 233	$ 3	$ 208
Valeria [Member]
Disclosure of detailed information about intangible assets [Line Items]
Gain on sales of undeveloped properties	83
Winchester South [Member]
Disclosure of detailed information about intangible assets [Line Items]
Gain on sales of undeveloped properties	$ 195

Intangible assets - Additional

Intangible assets - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about intangible assets [Line Items]
Exploration and evaluation costs	$ 488	$ 445	$ 497
Exploration and evaluation assets [Member]
Disclosure of detailed information about intangible assets [Line Items]
Capitalised related to projects which had not yet been approved to proceed	$ 233	420
Exploration and evaluation costs		393
Early works expenditure within property, plant and equipment		$ 27

Property, plant and equipment -

Property, plant and equipment - Summary of property, plant and equipment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	$ 62,093	$ 58,855
Adjustment on currency translation (c)	(4,157)	3,381
Adjustments to capitalised closure costs	486	710
Amounts capitalised	296	224	$ 111
Additions	5,301	4,751
Depreciation for the year (a) (e)	(3,882)	(4,198)	(4,567)
Impairment charges (f)	(130)	(435)
Disposals	(130)	(123)
Subsidiaries no longer consolidated (g)	(3,386)	(749)
Transfers and other movements (h)	(130)	(323)
Property, plant and equipment at end of period	56,361	62,093	58,855
Non-current assets held under finance leases (i)	31	37
Non-current assets pledged as security (j)	13,221	12,303
Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	115,889
Property, plant and equipment at end of period	104,294	115,889
Accumulated amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	(53,796)
Property, plant and equipment at end of period	(47,933)	(53,796)
Mining properties and leases [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	11,488	10,848
Adjustment on currency translation (c)	(689)	495
Adjustments to capitalised closure costs	486	710
Additions	403	230
Depreciation for the year (a) (e)	(664)	(673)
Impairment charges (f)	(3)	(304)
Disposals	(1)
Subsidiaries no longer consolidated (g)	(1,103)	(211)
Transfers and other movements (h)	1,146	393
Property, plant and equipment at end of period	11,063	11,488	10,848
Non-current assets pledged as security (j)	3,054	3,307
Mining properties and leases [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	24,691
Property, plant and equipment at end of period	23,318	24,691
Mining properties and leases [member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	(13,203)
Property, plant and equipment at end of period	(12,255)	(13,203)
Land and buildings [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	7,376	7,316
Adjustment on currency translation (c)	(548)	461
Additions	80	41
Depreciation for the year (a) (e)	(382)	(403)
Impairment charges (f)	(20)	(2)
Disposals	(54)	(57)
Subsidiaries no longer consolidated (g)	(377)	(95)
Transfers and other movements (h)	188	115
Property, plant and equipment at end of period	6,263	7,376	7,316
Non-current assets pledged as security (j)	385	410
Land and buildings [Member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	12,029
Property, plant and equipment at end of period	10,601	12,029
Land and buildings [Member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	(4,653)
Property, plant and equipment at end of period	(4,338)	(4,653)
Plant and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	36,285	35,706
Adjustment on currency translation (c)	(2,671)	2,242
Additions	459	646
Depreciation for the year (a) (e)	(2,836)	(3,122)
Impairment charges (f)	(101)	(128)
Disposals	(71)	(40)
Subsidiaries no longer consolidated (g)	(1,392)	(417)
Transfers and other movements (h)	2,346	1,398
Property, plant and equipment at end of period	32,019	36,285	35,706
Non-current assets held under finance leases (i)	31	37
Non-current assets pledged as security (j)	5,194	5,308
Plant and equipment [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	71,903
Property, plant and equipment at end of period	63,051	71,903
Plant and equipment [member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	(35,618)
Property, plant and equipment at end of period	(31,032)	(35,618)
Capital works in progress [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	6,944	4,985
Adjustment on currency translation (c)	(249)	183
Amounts capitalised	296	224
Additions	4,359	3,834
Impairment charges (f)	(6)	(1)
Disposals	(4)	(26)
Subsidiaries no longer consolidated (g)	(514)	(26)
Transfers and other movements (h)	(3,810)	(2,229)
Property, plant and equipment at end of period	7,016	6,944	$ 4,985
Non-current assets pledged as security (j)	4,588	3,278
Capital works in progress [member] | Cost [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	7,266
Property, plant and equipment at end of period	7,324	7,266
Capital works in progress [member] | Accumulated amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Property, plant and equipment at beginning of period	(322)
Property, plant and equipment at end of period	$ (308)	$ (322)

Property, plant and equipment_2

Property, plant and equipment - Summary of property, plant and equipment (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [Line Items]
Depreciation of property, plant and equipment	$ 3,882	$ 4,198	$ 4,567
Average borrowing rate used for capitalisation of interest	4.90%	4.45%
Loans secured by non-current assets collateral	$ 4,562	$ 4,677
Capitalised production phase stripping costs [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Capitalised production phase stripping costs, carrying amount	2,050	1,815
Capitalisation of property, plant and equipment	526
Capitalisation offset by depreciation	274
Capitalised production phase stripping costs [Member] | Property, plant and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Capitalised production phase stripping costs, carrying amount	1,572	1,374
Capitalised production phase stripping costs [Member] | Investment in equity accounted units [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Capitalised production phase stripping costs, carrying amount	478	441
Capitalised production phase stripping costs [Member] | Subsidiaries [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Depreciation of property, plant and equipment	134	194	$ 203
Freehold [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Land and buildings carrying amount	6,240	7,294
Long leasehold [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Land and buildings carrying amount	$ 23	82
Land [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	Not depreciated
Buildings [Member] | Bottom of range [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	5 years
Buildings [Member] | Top of range [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	50 years
Plant and equipment [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Depreciation of property, plant and equipment	$ 2,836	$ 3,122
Plant and equipment [member] | Bottom of range [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	3 years
Plant and equipment [member] | Top of range [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	P50Y
Power generating assets [Member] | Bottom of range [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	P25Y
Power generating assets [Member] | Top of range [Member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	P50Y
Capital works in progress [member]
Disclosure of detailed information about property, plant and equipment [Line Items]
Useful lives of property, plant and equipment	Not depreciated

Investments in equity account_3

Investments in equity accounted units - Summary of Investments in equity accounted units (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Investments in equity accounted units [Line Items]
– Non-current assets	$ 70,047	$ 76,554
– Current assets	20,168	18,678
Total assets	90,949	95,726
– Non-current liabilities	(30,261)	(33,262)
Total liabilities	(41,126)	(44,611)
Rio Tinto's share of net assets	4,299	4,486
Investment in equity accounted units [member]
Disclosure of Investments in equity accounted units [Line Items]
– Non-current assets	6,000	5,913
– Current assets	887	990
Total assets	6,887	6,903
– Current liabilities	(607)	(654)
– Non-current liabilities	(1,981)	(1,763)
Total liabilities	(2,588)	(2,417)
Rio Tinto's share of net assets	$ 4,299	$ 4,486	$ 5,019

Investments in equity account_4

Investments in equity accounted units - Additional information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Investments in equity accounted units [Line Items]
Investments in equity accounted units with shares listed on recognised stock exchanges	$ 0	$ 0
Net debt of the Group	(255,000,000)	3,845,000,000	$ 9,587,000,000
Investment in equity accounted units [member]
Disclosure of Investments in equity accounted units [Line Items]
Net debt of the Group	$ 1,158,000,000	$ 1,244,000,000

Inventories - Summary of invent

Inventories - Summary of inventories (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Classes Of Inventories [Abstract]
Raw materials and purchased components	$ 734	$ 648
Consumable stores	862	875
Work in progress	1,026	1,082
Finished goods and goods for resale	977	1,027
Total inventories	3,599	3,632
Expected to be used within one year	3,447	3,472
Expected to be used after more than one year	$ 152	$ 160

Inventories - Additional inform

Inventories - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Classes Of Inventories [Line Items]
Inventory write-downs, net of reversals	$ 48
Net inventory write- back		$ 7
Inventory partly write offs		74
Disclosure - Inventories - Additional information (Detail) [Line Items]
Inventories pledged as security for liabilities	$ 566	611
Previously Stated [Member]
Classes Of Inventories [Line Items]
Net inventory write- back		$ 81

Deferred Taxation - Reconciliat

Deferred Taxation - Reconciliation of changes in deferred tax liability asset (Detail) - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liability/(asset)			$ (607)
Adjustment on currency translation		$ (172)	53
Charged to the income statement		516	695
Charged to statement of comprehensive income		325	153	$ (33)
Disposals		(263)
Other movements		(32)	(61)
Deferred tax liability/(asset)	$ 162	536		$ (607)
– deferred tax liabilities		3,673	3,628
– deferred tax assets		(3,137)	(3,395)
Previously Stated [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liability/(asset)	233	$ 233
Deferred tax liability/(asset)			$ 233
Increase (decrease) due to application of IFRS 15 [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Adjustment to opening balance on transition to IFRS 15	$ (71)

Deferred Taxation - Deferred ta

Deferred Taxation - Deferred tax liabilities and assets, prior to offsetting of balances (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	$ 5,435	$ 6,440
Deferred tax assets	(4,899)	(6,207)
Charged/(credited) to the income statement	516	695
Capital allowances [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	4,408	5,208
Deferred tax assets	(154)	(579)
Charged/(credited) to the income statement	461	278
Unremitted earnings [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	454	588
Capitalised interest [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	259	391
Unrealised exchange gains (losses) [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	5	31
Deferred tax assets	(187)	(317)
Charged/(credited) to the income statement	57	36
Other temporary differences [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	309	222
Deferred tax assets	(786)	(682)
Charged/(credited) to the income statement	50	(235)
Tax losses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	(1,894)	(2,282)
Charged/(credited) to the income statement	(30)	12
Provisions [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	(1,585)	(1,731)
Charged/(credited) to the income statement	(19)	451
Post-retirement benefits [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	(293)	(616)
Charged/(credited) to the income statement	30	149
Tax on unremitted earnings [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Charged/(credited) to the income statement	$ (33)	$ 4

Deferred Taxation - Deferred _2

Deferred Taxation - Deferred tax liabilities and assets, prior to offsetting of balances (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	$ 3,673	$ 3,628
Deferred tax assets	3,137	3,395
Deferred tax is not recognised on the unremitted earnings of subsidiaries and joint ventures	3,726	3,242
Tax payable on unremitted earnings	$ 157	131
Deferred tax loss recovery period	6 years
Recognised and unrecognised deferred tax assets	$ 5,647	7,071
Unrecognised deferred tax assets	2,510	3,676
Unused tax losses [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	1,519	1,679
Later than one year [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	3,658	3,615
Deferred tax assets	$ 3,133	$ 3,386

Deferred Taxation - Recognised

Deferred Taxation - Recognised and unrecognised amounts in deferred tax assets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Recognised	$ 3,137	$ 3,395
Unrecognised	2,510	3,676
France [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Unrecognised	1,122	1,163
Canada [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Recognised	545	546
Unrecognised	559	674
United States [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Recognised	932	877
Unrecognised	12	7
Australia [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Recognised	796	1,055
Unrecognised	289	257
Mongolia [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Recognised	703	631
Unrecognised	87	61
Other countries [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Recognised	161	286
Unrecognised	$ 441	$ 1,514

Deferred Taxation - Recognise_2

Deferred Taxation - Recognised and unrecognised amounts in deferred tax assets (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	$ 3,137	$ 3,395
Deferred tax loss recovery period	6 years
Unrecognised deferred tax assets	$ 2,510	3,676
Realised or unrealised capital losses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	$ 96	250
Deferred tax loss recovery period	1 year
Unrecognised deferred tax assets	$ 684	777
Mongolia [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	703	631
Unrecognised deferred tax assets	87	61
Mongolia [Member] | Tax losses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	$ 469	$ 432
Deferred tax loss recovery period	8 years

Trade and other receivables - S

Trade and other receivables - Summary of trade and other receivables (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Trade And Other Receivables [Abstract]
Non-current trade receivables		$ 1
Non-current other financial receivables	$ 240	178
Non-current other receivables	129	348
Non-current prepayment of tolling charges to jointly controlled entities	228	269
Non-current pension surpluses	935	871
Non-current other prepayments	53	57
Total	1,585	1,724
Current trade receivables	2,167	2,314
Current other financial receivables	550	462
Current amounts due from equity accounted units	50	30
Current other receivables	226	358
Current other prepayments	186	279
Total	3,179	3,443
Trade receivables	2,167	2,315
Other financial receivables	790	640
Amounts due from equity accounted units	50	30
Other receivables	355	706
Prepayment of tolling charges to jointly controlled entities	228	269
Pension surpluses	935	871
Other prepayments	239	336
Total	$ 4,764	$ 5,167

Trade and other receivables -_2

Trade and other receivables - Summary of trade and other receivables (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Trade And Other Receivables [Line Items]
Net of provisions for doubtful debts	$ 8
Increase in provision	2
Provision utilised	$ 42
IAS 39 [member]
Trade And Other Receivables [Line Items]
Net of provisions for doubtful debts		$ 55
IFRS 9 [member]
Trade And Other Receivables [Line Items]
Net of provisions for doubtful debts		$ 7

Assets and liabilities held f_3

Assets and liabilities held for sale - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Rossing Uranium [member] | Mining properties [member]
Disclosure Of Assets And Liabilities Held For Sale Line Item
Expected loss on asset held for sale	$ 300
Assets and liabilities classified as held for sale [member] | Rossing Uranium [member]
Disclosure Of Assets And Liabilities Held For Sale Line Item
Ownership interest in subsidiary	106
Assets and liabilities classified as held for sale [member] | ISAL Smelter [member]
Disclosure Of Assets And Liabilities Held For Sale Line Item
Ownership interest in subsidiary	$ 334
Assets and liabilities classified as held for sale [member] | Dunkerque Aluminium Smelter [Member]
Disclosure Of Assets And Liabilities Held For Sale Line Item
Ownership interest in subsidiary		$ 355

Assets and liabilities held f_4

Assets and liabilities held for sale - Summary of major classes of assets and liabilities classified as held for sale (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Intangible assets	$ 2,779	$ 3,119	$ 3,279
Property, plant and equipment	56,361	62,093	$ 58,855
Investments in equity accounted units	4,299	4,486
Deferred tax assets	3,137	3,395
Cash and cash equivalents	10,773	10,550
Liabilities
Liabilities of disposal groups held for sale	(294)	(124)
Net assets	49,823	51,115
Assets and liabilities classified as held for sale [member]
Assets
Intangible assets	4	6
Property, plant and equipment	238	190
Investments in equity accounted units	5
Inventories	186	88
Deferred tax assets	66	49
Trade and other receivables	58	139
Other financial assets (including loans to equity accounted units)	60	22
Cash and cash equivalents	117
Assets of disposal groups held for sale	734	494
Liabilities
Trade and other payables	(134)	(60)
Provisions including post-retirement benefits	(160)	(64)
Liabilities of disposal groups held for sale	(294)	(124)
Net assets	$ 440	$ 370

Other financial assets (inclu_3

Other financial assets (including non-quasi equity loans to equity accounted units) - Summary of other financial assets including non-quasi equity loans to equity accounted units (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Other Assets [Abstract]
Non-current derivative financial instruments	$ 468	$ 238
Non-current equity shares and quoted funds	53	45
Other non-current investments, including loans	255	188
Non-current loans to equity accounted units	38	39
Other financial assets (including loans to equity accounted units)	814	510
Current derivative financial instruments	88	29
Current equity shares and quoted funds	77	91
Other current investments, including loans	2,527	964
Other financial assets (including loans to equity accounted units)	2,692	1,084
Derivative financial instruments	556	267
Equity shares and quoted funds	130	136
Other investments, including loans	2,782	1,152
Loans to equity accounted units	38	39
Total	$ 3,506	$ 1,594

Other financial assets (inclu_4

Other financial assets (including non-quasi equity loans to equity accounted units) - Summary of other financial assets including non-quasi equity loans to equity accounted units (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Other Assets [Abstract]
Highly liquid financial assets held in managed investment funds classified as held for trading	$ 2,522	$ 958

Cash and cash equivalents - Sum

Cash and cash equivalents - Summary of cash and cash equivalents (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Cash at bank and in hand	$ 740	$ 1,035
Money market funds and other cash equivalents	10,033	9,515
Balance per Group balance sheet	10,773	10,550
Bank overdrafts repayable on demand (unsecured)	(1)	(3)
Cash and cash equivalents included in Assets held for sale	117
Balance per Group cash flow statement	$ 10,889	$ 10,547	$ 8,189	$ 9,354

Cash and cash equivalents - Add

Cash and cash equivalents - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of cash and cash equivalents [Line Items]
Restricted cash and cash equivalents	$ 186	$ 290
Repayment of third party borrowings	142	158
Subsidiaries [Member]
Disclosure of cash and cash equivalents [Line Items]
Restricted cash and cash equivalents	1,090	1,089
Repayment of third party borrowings	$ 864	$ 703

Borrowings and other financia_3

Borrowings and other financial liabilities - Summary of detailed information about borrowings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of detailed information about borrowings [Line Items]
Non-current borrowing	$ 12,440	$ 14,624
Current borrowings including overdrafts	312	552
Total borrowings	$ 12,752	$ 15,176
Rio Tinto Finance plc Euro Bonds 2.0% due 2020 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	2.00%	2.00%
Borrowing maturity	2,020	2,020
Non-current borrowing	$ 468	$ 921
Total borrowings	$ 468	$ 921
Rio Tinto Finance (USA) Limited Bonds 4.125% 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	4.125%	4.125%
Borrowing maturity	2,021	2,021
Non-current borrowing		$ 428
Total borrowings		$ 428
Rio Tinto Finance (USA) Limited Bonds 3.750% 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	3.75%	3.75%
Borrowing maturity	2,021	2,021
Non-current borrowing		$ 347
Total borrowings		$ 347
Rio Tinto Finance (USA) plc Bonds 3.5% 2022 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	3.50%	3.50%
Borrowing maturity	2,022	2,022
Non-current borrowing		$ 227
Total borrowings		$ 227
Rio Tinto Finance (USA) plc Bonds 2.875% 2022 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	2.875%	2.875%
Borrowing maturity	2,022	2,022
Non-current borrowing		$ 377
Total borrowings		$ 377
Rio Tinto Finance plc Euro Bonds 2.875% due 2024 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	2.875%	2.875%
Borrowing maturity	2,024	2,024
Non-current borrowing	$ 514	$ 644
Total borrowings	$ 514	$ 644
Rio Tinto Finance (USA) Limited Bonds 3.75% 2025 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	3.75%	3.75%
Borrowing maturity	2,025	2,025
Non-current borrowing	$ 1,170	$ 1,192
Total borrowings	$ 1,170	$ 1,192
Rio Tinto Finance (USA) Limited Bonds 7.125% 2028 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	7.125%	7.125%
Borrowing maturity	2,028	2,028
Non-current borrowing	$ 927	$ 965
Total borrowings	$ 927	$ 965
Alcan Inc. Debentures 7.25% due 2028 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	7.25%	7.25%
Borrowing maturity	2,028	2,028
Non-current borrowing	$ 104	$ 105
Total borrowings	$ 104	$ 105
Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	4.00%	4.00%
Borrowing maturity	2,029	2,029
Non-current borrowing	$ 633	$ 669
Total borrowings	$ 633	$ 669
Alcan Inc. Debentures 7.25% due 2031 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	7.25%	7.25%
Borrowing maturity	2,031	2,031
Non-current borrowing	$ 421	$ 422
Total borrowings	$ 421	$ 422
Alcan Inc. Global Notes 6.125% due 2033 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	6.125%	6.125%
Borrowing maturity	2,033	2,033
Non-current borrowing	$ 741	$ 740
Total borrowings	$ 741	$ 740
Alcan Inc. Global Notes 5.75% due 2035 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	5.75%	5.75%
Borrowing maturity	2,035	2,035
Non-current borrowing	$ 288	$ 287
Total borrowings	$ 288	$ 287
Rio Tinto Finance (USA) Limited Bonds 5.2% 2040 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	5.20%	5.20%
Borrowing maturity	2,040	2,040
Non-current borrowing	$ 1,095	$ 1,102
Total borrowings	$ 1,095	$ 1,102
Rio Tinto Finance (USA) plc Bonds 4.75% 2042 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	4.75%	4.75%
Borrowing maturity	2,042	2,042
Non-current borrowing	$ 462	$ 467
Total borrowings	$ 462	$ 467
Oyu Tolgoi LLC MIGA Insured Loan LIBOR plus 2.65% due 2027 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	2.65%	2.65%
Borrowing maturity	2,027	2,027
Non-current borrowing	$ 676	$ 674
Total borrowings	$ 676	$ 674
Rio Tinto Finance (USA) plc Bonds 4.125% 2042 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	4.125%	4.125%
Borrowing maturity	2,042	2,042
Non-current borrowing	$ 685	$ 691
Total borrowings	$ 685	$ 691
Oyu Tolgoi LLC Commercial Banks "B Loan" LIBOR plus 3.4% due 2027 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	3.40%	3.40%
Borrowing maturity	2,027	2,027
Non-current borrowing	$ 1,588	$ 1,588
Total borrowings	$ 1,588	$ 1,588
Oyu Tolgoi LLC Export Credit Agencies Loan 2.3% due 2028 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	2.30%	2.30%
Borrowing maturity	2,028	2,028
Non-current borrowing	$ 272	$ 255
Total borrowings	$ 272	$ 255
Oyu Tolgoi LLC Export Credit Agencies Loan LIBOR plus 3.65% due 2029 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	3.65%	3.65%
Borrowing maturity	2,029	2,029
Non-current borrowing	$ 871	$ 869
Total borrowings	$ 871	$ 869
Oyu Tolgoi LLC International Financial Instritutions "A Loan" LIBOR plus 3.78% due 2030 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings, interest rate	3.78%	3.78%
Borrowing maturity	2,030	2,030
Non-current borrowing	$ 768	$ 761
Total borrowings	768	761
Loans from equity accounted units [member]
Disclosure of detailed information about borrowings [Line Items]
Current borrowings including overdrafts		31
Total borrowings		31
Other secured loans [member]
Disclosure of detailed information about borrowings [Line Items]
Non-current borrowing	345	451
Current borrowings including overdrafts	42	79
Total borrowings	387	530
Other unsecured loans [member]
Disclosure of detailed information about borrowings [Line Items]
Non-current borrowing	373	393
Current borrowings including overdrafts	264	435
Total borrowings	637	828
Finance leases [member]
Disclosure of detailed information about borrowings [Line Items]
Non-current borrowing	39	49
Current borrowings including overdrafts	5	4
Total borrowings	44	53
Bank overdrafts [member]
Disclosure of detailed information about borrowings [Line Items]
Current borrowings including overdrafts	1	3
Total borrowings	$ 1	$ 3

Borrowings and other financia_4

Borrowings and other financial liabilities - Summary of detailed information about borrowings (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of detailed information about borrowings [Line Items]
Cumulative amount utilised from debt issuance	$ 1,600	$ 2,200
Carrying value of bonds	$ 1,600	2,200
Increase in stated percentage	1.00%
Borrowings	$ 12,752	15,176
Subsidiary borrowings	2,400	2,700
Debt instrument restrictive covenants	4,600	4,700
European debt issuance programme [member]
Disclosure of detailed information about borrowings [Line Items]
Notional amount	$ 10,000	$ 10,000

Borrowings and other financia_5

Borrowings and other financial liabilities - Summary of borrowings and other financial liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of borrowings and other financial liabilities [Line Items]
Borrowings and other financial liabilities	$ 12,847	$ 15,148
Total non-current borrowings including overdrafts (as above)	12,440	14,624
Total other current financial liabilities	1,073	904
Total current borrowings including overdrafts (as above)	312	552
Total current borrowings and other financial liabilities	1,073	904
Total borrowings including overdrafts (as above)	12,752	15,176
Total borrowings and other financial liabilities	13,920	16,052
Derivative financial instruments [member]
Disclosure of borrowings and other financial liabilities [Line Items]
Borrowings and other financial liabilities	407	481
Total other current financial liabilities	95	50
Total other financial liabilities	502	531
Other financial liability [Member]
Disclosure of borrowings and other financial liabilities [Line Items]
Borrowings and other financial liabilities		43
Total other current financial liabilities	666	302
Total other financial liabilities	666	345
Total Other financial liabilities [member]
Disclosure of borrowings and other financial liabilities [Line Items]
Borrowings and other financial liabilities	407	524
Total other current financial liabilities	761	352
Total other financial liabilities	$ 1,168	$ 876

Borrowings and other financia_6

Borrowings and other financial liabilities - Additional information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Disclosure of detailed information about borrowings [Line Items]
Derivative financial assets	$ 556,000,000	$ 267,000,000
Derivative financial liabilities	(502,000,000)	(531,000,000)
Interest rate swaps [member]
Disclosure of detailed information about borrowings [Line Items]
Derivative financial liabilities	358,000,000	276,000,000
Rio Tinto Finance (USA) Limited Bonds 7.125% 2028 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings at amortised cost	75,000,000	75,000,000
Interest rate swaps [member]
Disclosure of detailed information about borrowings [Line Items]
Derivative financial assets	70,000,000	99,000,000
Cross currency interest rate swaps [member] | Rio Tinto Finance plc Sterling Bonds 4.0% due 2029 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings notional amount	600,000,000	700,000,000
US Dollars [Member] | Interest rate swaps [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings notional amount	4,300,000,000	5,700,000,000
Euro Member Countries, Euro | Interest rate swaps [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings notional amount	$ 900,000,000	$ 1,500,000,000

Capitalised finance leases - Su

Capitalised finance leases - Summary of capitalised finance leases (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Maturity Analysis Of Finance Lease Payments Payable [Line Items]
Total minimum lease payments undiscounted	$ 45	$ 57
Effect of discounting	(1)	(4)
Total	44	53
Due within 1 year [member]
Disclosure Of Maturity Analysis Of Finance Lease Payments Payable [Line Items]
Present value of minimum lease payments	5	4
Between 1 and 3 years [member]
Disclosure Of Maturity Analysis Of Finance Lease Payments Payable [Line Items]
Present value of minimum lease payments	10	14
Between 3 and 5 years [member]
Disclosure Of Maturity Analysis Of Finance Lease Payments Payable [Line Items]
Present value of minimum lease payments	18	28
More than 5 years [member]
Disclosure Of Maturity Analysis Of Finance Lease Payments Payable [Line Items]
Present value of minimum lease payments	$ 12	$ 11

Consolidated net cash_(debt) -

Consolidated net cash/(debt) - Analysis of changes in consolidated net cash/(debt) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial liabilities [Abstract]
Net debt at beginning balance	$ (3,845)	$ (9,587)
Foreign exchange adjustment	213	(70)
Cash movements excluding exchange movements, net debt	4,045	5,859
Other non-cash movements	(158)	(47)
Net debt at ending balance	255	(3,845)
Borrowings (including finance leases) Excluding Overdraft [Member]
Disclosure of financial liabilities [Abstract]
Financial liabilities, beginning balance	(15,173)	(17,618)
Foreign exchange adjustment	126	(303)
Cash movements excluding exchange movements	2,246	2,777
Other non-cash movements	50	(29)
Financial liabilities, ending balance	(12,751)	(15,173)
Debt-related derivatives (included in "Other financial assets/liabilities) [member]
Disclosure of financial liabilities [Abstract]
Financial liabilities, beginning balance	(177)	(408)
Foreign exchange adjustment	(64)	245
Cash movements excluding exchange movements	51	7
Other non-cash movements	(98)	(21)
Financial liabilities, ending balance	(288)	(177)
Other Investments [Member]
Disclosure of financial liabilities [Abstract]
Cash and Overdrafts, Beginning balance	10,547	8,189
Foreign exchange adjustment	151	(12)
Cash movements excluding exchange movements	191	2,370
Other non-cash movements	(117)
Cash and Overdrafts, ending balance	10,772	10,547
Other Investments [Member]
Disclosure of financial liabilities [Abstract]
Cash and Overdrafts, Beginning balance	958	250
Cash movements excluding exchange movements	1,557	705
Other non-cash movements	7	3
Cash and Overdrafts, ending balance	$ 2,522	$ 958

Consolidated net cash_(debt) _2

Consolidated net cash/(debt) - Analysis of changes in consolidated net cash/(debt) (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial liabilities [Abstract]
Overdrafts	$ 1	$ 3
Total other current financial liabilities	1,073	904
Highly liquid financial assets held in managed investment funds classified as held for trading	2,522	958
Borrowings (including finance leases) Excluding Overdraft [Member]
Disclosure of financial liabilities [Abstract]
Overdrafts	1	3
Total other current financial liabilities	761	352
Other current non-financial liabilities	407	524
Over Draft
Disclosure of financial liabilities [Abstract]
Overdrafts	$ 1	$ 3

Trade and other payables - Summ

Trade and other payables - Summary of Trade and other payables (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Trade And Other Payables [Abstract]
Non-current other financial payables	$ 256	$ 265
Non-current other payables	165	87
Non-current deferred income	176	246
Non-current accruals	11	13
Non-current royalties and mining taxes	1	4
Non-current amounts owed to equity accounted units	156	156
Non-current government grants deferred	76	85
Total	841	856
Current trade payables	3,180	3,255
Current other financial payables	653	867
Current other payables	114	97
Current deferred income	234	246
Current accruals	1,229	1,347
Current employee entitlements	630	734
Current royalties and mining taxes	487	492
Current amounts owed to equity accounted units	67	19
Current government grants deferred	6	4
Total	6,600	7,061
Trade payables	3,180	3,255
Other financial payables	909	1,132
Other payables	279	184
Deferred income	410	492
Accruals	1,240	1,360
Employee entitlements	630	734
Royalties and mining taxes	488	496
Amounts owed to equity accounted units	223	175
Government grants deferred	82	89
Total	$ 7,441	$ 7,917

Trade and other payables - Su_2

Trade and other payables - Summary of Trade and other payables (Parenthetical) (Detail) $ in Millions	Dec. 31, 2018USD ($)
Trade And Other Payables [Abstract]
Contract liabilities	$ 198

Provisions, including post-reti

Provisions, including post-retirement benefits - Summary of Provisions, including post-retirement benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disclosure of other provisions [Line Items]
Provisions (including post-retirement benefits) at beginning balance	$ 14,642	$ 13,794
Adjustment on currency translation	(898)	846
Adjustments to mining properties:
– changes in estimate	486	710
Charged/(credited) to profit:
– increases to existing and new provisions	1,137	797
– unused amounts reversed	(144)	(187)
– exchange losses/(gains) on provisions	16	(83)
– amortisation of discount	381	383
Utilised in year	(837)	(1,053)
Actuarial (gains)/losses recognised in equity	(781)	121
Subsidiaries no longer consolidated	(318)	(622)
Transfers and other movements	(76)	(64)
Provisions (including post-retirement benefits) at ending balance	13,608	14,642
Balance sheet analysis:
Current			$ 1,056	$ 1,275
Non-current			12,552	13,367
Total	14,642	14,642	13,608	14,642
Pensions and post retirement healthcare [member]
Disclosure of other provisions [Line Items]
Provisions (including post-retirement benefits) at beginning balance	3,370
Adjustment on currency translation	(145)
Charged/(credited) to profit:
– increases to existing and new provisions	267
Utilised in year	(219)
Actuarial (gains)/losses recognised in equity	(781)
Transfers and other movements	(6)
Provisions (including post-retirement benefits) at ending balance	2,486	3,370
Balance sheet analysis:
Current			79
Non-current			2,407
Total	3,370	3,370	2,486	3,370
Other employee entitlements [member]
Disclosure of other provisions [Line Items]
Provisions (including post-retirement benefits) at beginning balance	389
Adjustment on currency translation	(37)
Charged/(credited) to profit:
– increases to existing and new provisions	185
– unused amounts reversed	(36)
Utilised in year	(122)
Subsidiaries no longer consolidated	(29)
Transfers and other movements	10
Provisions (including post-retirement benefits) at ending balance	360	389
Balance sheet analysis:
Current			274
Non-current			86
Total	389	389	360	389
Close down and restoration/ environmental [member]
Disclosure of other provisions [Line Items]
Provisions (including post-retirement benefits) at beginning balance	9,983
Adjustment on currency translation	(656)
Adjustments to mining properties:
– changes in estimate	486
Charged/(credited) to profit:
– increases to existing and new provisions	456
– unused amounts reversed	(38)
– exchange losses/(gains) on provisions	13
– amortisation of discount	372
Utilised in year	(319)
Subsidiaries no longer consolidated	(257)
Transfers and other movements	(65)
Provisions (including post-retirement benefits) at ending balance	9,975	9,983
Balance sheet analysis:
Current			476
Non-current			9,499
Total	9,983	9,983	9,975	9,983
Other [member]
Disclosure of other provisions [Line Items]
Provisions (including post-retirement benefits) at beginning balance	900
Adjustment on currency translation	(60)
Charged/(credited) to profit:
– increases to existing and new provisions	229
– unused amounts reversed	(70)
– exchange losses/(gains) on provisions	3
– amortisation of discount	9
Utilised in year	(177)
Subsidiaries no longer consolidated	(32)
Transfers and other movements	(15)
Provisions (including post-retirement benefits) at ending balance	787	900
Balance sheet analysis:
Current			227
Non-current			560
Total	$ 900	$ 900	$ 787	$ 900

Provisions, including post-re_2

Provisions, including post-retirement benefits - Summary of Provisions, including post-retirement benefits (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of other provisions [Line Items]
Remaining lives of operations and infrastructure present closure obligation	17 years	20 years
Remaining lives of operations and infrastructure	one to over 60 years
Close-down and restoration costs and environmental clean-up obligations	$ 9,975	$ 9,983
Risk free interest rate on provisions	2.00%
Provision	$ 13,608	14,642	$ 13,794
Non-current provisions	$ 12,552	$ 13,367
Diavik Diamond Mines (2012) Inc. [Member]
Disclosure of other provisions [Line Items]
Adjustment to record obligations for close-down and restoration	100.00%	60.00%
Bottom of range [Member]
Disclosure of other provisions [Line Items]
Risk free interest rate on provisions	0.50%
Top of range [Member]
Disclosure of other provisions [Line Items]
Provision	$ 1,139
Other employee entitlements [member]
Disclosure of other provisions [Line Items]
Provision for long service leave	242	$ 292
Provision for redundancy and severance payments	46	24
Provision	360	389
Non-current provisions	86
Close down and restoration/ environmental [member]
Disclosure of other provisions [Line Items]
Provision	9,975	9,983
Non-current provisions	9,499
Provisions relating to insurance recoveries and other financial assets held	110	75
Close down and restoration/ environmental [member] | Between 1 and 5 years [Member]
Disclosure of other provisions [Line Items]
Non-current provisions	535	336
Close down and restoration/ environmental [member] | After 5 years [Member]
Disclosure of other provisions [Line Items]
Non-current provisions	$ 683	$ 839

Share capital - Rio Tinto plc -

Share capital - Rio Tinto plc - Summary of share capital (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Classes Of Share Capital [Line Items]
Rio Tinto Limited shares were held by Rio Tinto plc	0	0	0
Rio Tinto plc [member]
Disclosure Of Classes Of Share Capital [Line Items]
Issued and fully paid up share capital at beginning balance	$ 220,000	$ 224,000	$ 224,000
Shares purchased and cancelled	(9,000)	(4,000)
Issued and fully paid up share capital at ending balance	$ 211,000	$ 220,000	$ 224,000
Number of issued and fully paid up share capital at beginning balance	1,351,609,000	1,384,520,000	1,384,487,000
Number of shares held by public at beginning balance	1,351,609,000	1,384,520,000
Ordinary shares issued	35,380	26,241	33,210
Shares purchased and cancelled	$ (63,984)	$ (32,937)
Shares purchased and cancelled	(63,984,287)	(32,937,109)	0
Number of issued and fully paid up share capital at ending balance	1,287,660,000	1,351,609,000	1,384,520,000
Number of shares held by public at ending balance	1,287,660,000	1,351,609,000	1,384,520,000
Rio Tinto plc [member] | Shares held by public [member]
Disclosure Of Classes Of Share Capital [Line Items]
Number of shares held by public at beginning balance	1,342,058,000	1,374,822,000	1,374,046,000
Ordinary shares issued	35,000	26,000	33,000
Shares reissued from treasury	106,000	147,000	743,000
Shares purchased and cancelled	(63,984,000)	(32,937,000)
Rio Tinto Limited shares were held by Rio Tinto plc	9,445,000	9,551,000	9,698,000
Number of shares held by public at ending balance	1,278,215,000	1,342,058,000	1,374,822,000
Rio Tinto plc [member] | Special voting share [member]
Disclosure Of Classes Of Share Capital [Line Items]
Other share classes	1 only	1 only	1 only
Rio Tinto plc [member] | DLC dividend share [member]
Disclosure Of Classes Of Share Capital [Line Items]
Other share classes	1 only	1 only	1 only
Rio Tinto plc [member] | Equalisation share [member]
Disclosure Of Classes Of Share Capital [Line Items]
Other share classes	1 only	1 only	1 only

Share capital - Rio Tinto plc_2

Share capital - Rio Tinto plc - Summary of share capital (Parenthetical) (Detail) - Rio Tinto plc [member] $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)shares	Dec. 31, 2018USD ($)£ / sharesshares	Dec. 31, 2017USD ($)shares	Dec. 31, 2017USD ($)£ / sharesshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2016USD ($)£ / sharesshares	Dec. 31, 2015USD ($)
Disclosure Of Classes Of Share Capital [Line Items]
Ordinary shares issued	35,380	35,380	26,241	26,241	33,210	33,210
Number of shares bought back	63,984,287		32,937,109		0
Share capital | $	$ 211	$ 211	$ 220	$ 220	$ 224	$ 224	$ 224
Treasury stock reissued | $	$ 6		$ 2		$ 4
Rio Tinto Plc employee share based payment plans [member]
Disclosure Of Classes Of Share Capital [Line Items]
Ordinary shares issued	0	0	0	0	0	0
Exercise prices per share | £ / shares		$ 16.53		$ 28.63		$ 16.53
Market value per share | £ / shares		$ 43.79		$ 37.78		$ 32.23
Rio Tinto Plc employee share based payment plans [member] | Treasury shares [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Shares reissued from treasury	106,045		147,126		743,380
Global employee share plan [member]
Disclosure Of Classes Of Share Capital [Line Items]
Share capital | $	$ 1	$ 1	$ 1	$ 1	$ 0.9	$ 0.9

Share capital - Rio Tinto plc_3

Share capital - Rio Tinto plc - Additional information (Detail) - USD ($) $ in Millions	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
American depository receipts [member]
Disclosure Of Classes Of Share Capital [Line Items]
Value of shares purchased by employee share ownership trusts		$ 140	$ 38.9	$ 40.1
Rio Tinto plc [member]
Disclosure Of Classes Of Share Capital [Line Items]
Shares held in the employee share ownership trusts on behalf of Rio Tinto plc		1,770,651
Number of shares bought back		63,984,287	32,937,109	0
Rio Tinto plc [member] | Major ordinary share transactions [member]
Disclosure Of Classes Of Share Capital [Line Items]
Number of shares bought back	10,956,767
Rio Tinto plc [member] | American depository receipts [member]
Disclosure Of Classes Of Share Capital [Line Items]
ADRs held by the Employee share ownership Trust (ESOT)		72,809

Share capital - Rio Tinto Lim_3

Share capital - Rio Tinto Limited - Summary of share capital (Detail) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Classes Of Share Capital [Line Items]
Adjustment on currency translation			$ 386
Rio Tinto Limited [member]
Disclosure Of Classes Of Share Capital [Line Items]
Issued and fully paid up share capital at beginning balance			4,140	$ 3,915	$ 3,950
Adjustment on currency translation			(382)	310	(35)
Ordinary shares purchased and cancelled			(281)	(85)
Issued and fully paid up share capital at ending balance			$ 3,477	$ 4,140	$ 3,915
Number of issued and fully paid up share capital at beginning balance			412,410,000	424,190,000	424,190,000
Ordinary shares purchased and cancelled	(41,198,134)	(11,778,064)	(41,200,000)	(11,780,000)
Number of issued and fully paid up share capital at ending balance			371,210,000	412,410,000	424,190,000
Rio Tinto Limited [member] | Special voting share [member]
Disclosure Of Classes Of Share Capital [Line Items]
Other share classes			1 only	1 only	1 only
Rio Tinto Limited [member] | DLC dividend share [member]
Disclosure Of Classes Of Share Capital [Line Items]
Other share classes			1 only	1 only	1 only

Share capital - Rio Tinto Lim_4

Share capital - Rio Tinto Limited - Summary of share capital (Parenthetical) (Detail) - Rio Tinto Limited [member] - د.إ / shares	1 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Classes Of Share Capital [Line Items]
Ordinary shares purchased and cancelled	41,198,134	11,778,064	41,200,000	11,780,000
Price per purchased share	د.إ 69.69	د.إ 63.67
Top of range [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Number of shares bought back	41,200,000	42,400,000

Share capital - Rio Tinto Lim_5

Share capital - Rio Tinto Limited - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Classes Of Share Capital [Line Items]
Rio Tinto Limited shares were held by Rio Tinto plc	0	0	0
Rio Tinto Limited [member]
Disclosure Of Classes Of Share Capital [Line Items]
Value of shares purchased by employee share ownership trusts	$ 114	$ 37.5	$ 48.5
Rio Tinto Limited shares were held by Rio Tinto plc	1,416,728

Other reserves and retained e_3

Other reserves and retained earnings - Summary of other reserves and retained earnings (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance		$ 12,284
Change in equity interest held by Rio Tinto	[1]					$ (165)
Own shares purchased from Rio Tinto shareholders to satisfy share options		(254)	[2]	$ (82)	[2]	(80)
Companies no longer consolidated				(2)		8
Ending balance		8,661		12,284
Parent and subsidiaries currency translation and exchange adjustments		213		(70)
Beginning balance		23,761
Tax relating to components of other comprehensive income		(325)		(153)		33
Dividends		(5,771)		(4,653)		(3,077)
Employee share options and other IFRS 2 charges to the income statement		111		98		125
Ending balance		27,025		23,761
Capital redemption reserve [Member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance		38		34		34
Own shares purchased and cancelled		9		4
Ending balance		47		38		34
Cash flow hedge reserve [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance		32		32
Adjustment for transition to new accounting standards (note 45)		(4)
Cash flow hedge gains/(losses)		156		62		(88)
Cash flow hedge losses/(gains) transferred to the income statement		40		(62)		116
Tax on the above		(54)				4
Transfers and other movements		25
Ending balance		195		32		32
Available for sale revaluation reserves [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance		20		(126)		(139)
Adjustment for transition to new accounting standards (note 45)		(20)
Gains on available for sale securities				19		13
Losses on available for sale securities transferred to the income statement				6
Tax on the above				(1)
Transfers and other movements				122
Ending balance				20		(126)
Fair Value through Other Comprehensive Income reserve [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Adjustment for transition to new accounting standards (note 45)		8
Losses on equity investments		(11)
Transfers to retained earnings		(3)
Ending balance		(6)
Cost of Hedging Reserve [Member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Adjustment for transition to new accounting standards (note 45)		26
Cost of hedging deferred to reserves during the year		(36)
Transfer of cost of hedging to the income statement		(3)
Ending balance		(13)
Other reserves [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance		11,714		11,861		11,735
Change in equity interest held by Rio Tinto						108
Own shares purchased from Rio Tinto Limited shareholders to satisfy share options		(114)		(64)		(43)
Own shares purchased from Rio Tinto shareholders to satisfy share options		52		31		58
Deferred tax on share options		(2)		10		3
Companies no longer consolidated				(124)
Ending balance		11,650		11,714		11,861
Foreign currency translation reserve [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance		12,284		9,216
Ending balance		8,661		12,284		9,216
Beginning balance		480		(2,585)		(2,491)
Parent and subsidiaries currency translation and exchange adjustments		(3,658)		2,942		(204)
Equity accounted units currency translation adjustments		(48)		34		11
Currency translation reclassified on disposal		14		78		99
Transfers and other movements				11
Ending balance		(3,212)		480		(2,585)
Retained earnings [Member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Change in equity interest held by Rio Tinto		60		43		40	[1]
Own shares purchased from Rio Tinto Limited shareholders to satisfy share options		(22)		(133)
Own shares purchased from Rio Tinto shareholders to satisfy share options		(140)	[2]	(18)	[2]	(37)
Companies no longer consolidated				130
Beginning balance		23,761		21,631		19,736
Adjustment for transition to new accounting standards (note 45)		(179)
Parent and subsidiaries' profit for the year		13,125		8,423		4,298
Equity accounted units' profit after tax for the year		513		339		319
Actuarial gains/(losses)		894		1		(94)
Tax relating to components of other comprehensive income		(269)		(150)		30
Total comprehensive income for the year		14,263		8,613		4,553
Share buy-back programme		(5,423)		(2,312)
Dividends		(5,356)		(4,250)		(2,725)
Companies no longer consolidated				130
Employee share options and other IFRS 2 charges to the income statement		61		57		64
Transfer from FVOCI reserve		3
Transfers and other movements		(25)		(133)
Ending balance		$ 27,025		$ 23,761		$ 21,631
[1]	The restructure of Coal & Allied Industries Limited completed on 3 February 2016. The restructure involved the exchange of a 32.4% interest in Hunter Valley Operations mine for an additional 20% shareholding in Coal & Allied Industries Limited, increasing Rio Tinto’s shareholding of Coal & Allied Industries Limited from 80% to 100%. Rio Tinto sold its 100% interest in Coal & Allied Industries Limited on 1 September 2017.
[2]	Net of contributions received from employees for share options.

Other reserves and retained e_4

Other reserves and retained earnings - Summary of other reserves and retained earnings (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Share premium account	$ 4,312,000,000	$ 4,306,000,000
Other reserve, share premium	8,661,000,000	12,284,000,000
Actuarial losses to equity accounted units	(1,382,000,000)	855,000,000	$ 1,120,000,000
Investment in equity accounted units [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Actuarial losses to equity accounted units	0	$ 0	$ 0
Share premium [Member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Share premium account	0
Merger reserve [Member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Other reserve, share premium	$ 11,936,000,000

Financial instruments and ris_3

Financial instruments and risk management - Summary of financial assets by categories (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial assets [Line Items]
Cash and cash equivalents	$ 10,773	$ 10,550
Trade and other financial receivables	3,007	2,985
Equity shares and quoted funds	130	136
Other investments, including loans	2,782	1,152
IFRS 9 [member]
Disclosure of financial assets [Line Items]
Cash and cash equivalents	10,773
Trade and other financial receivables	3,007
Equity shares and quoted funds	130
Other investments, including loans	2,782
Derivatives related to net debt: designated as hedges	70
Derivatives and embedded derivatives not related to net debt: not designated as hedges	432
Embedded derivatives not related to net debt: designated as hedges	54
Loans to equity accounted units including quasi equity loans	167
Total financial assets	17,415
IFRS 9 [member] | Amortised Cost [member]
Disclosure of financial assets [Line Items]
Cash and cash equivalents	2,779
Trade and other financial receivables	2,015
Other investments, including loans	6
Loans to equity accounted units including quasi equity loans	167
Total financial assets	4,967
IFRS 9 [member] | Fair value through other comprehensive income [member]
Disclosure of financial assets [Line Items]
Equity shares and quoted funds	53
Total financial assets	53
IFRS 9 [member] | Fair value through profit and loss [member]
Disclosure of financial assets [Line Items]
Cash and cash equivalents	7,994
Trade and other financial receivables	992
Equity shares and quoted funds	77
Other investments, including loans	2,776
Derivatives related to net debt: designated as hedges	70
Derivatives and embedded derivatives not related to net debt: not designated as hedges	432
Embedded derivatives not related to net debt: designated as hedges	54
Total financial assets	$ 12,395
IAS 39 [Member]
Disclosure of financial assets [Line Items]
Cash and cash equivalents		10,550
Trade and other financial receivables		2,985
Equity shares and quoted funds		136
Other investments, including loans		1,152
Derivatives related to net debt: designated as hedges		99
Derivatives and embedded derivatives not related to net debt: not designated as hedges		168
Loans to equity accounted units including quasi equity loans		198
Total financial assets		15,288
IAS 39 [Member] | Loans and receivables [member]
Disclosure of financial assets [Line Items]
Cash and cash equivalents		10,550
Trade and other financial receivables		2,895
Other investments, including loans		15
Loans to equity accounted units including quasi equity loans		198
Total financial assets		13,658
IAS 39 [Member] | Available for sale securities [member]
Disclosure of financial assets [Line Items]
Equity shares and quoted funds		136
Total financial assets		136
IAS 39 [Member] | Held at fair value [member]
Disclosure of financial assets [Line Items]
Trade and other financial receivables		90
Other investments, including loans		1,125
Derivatives related to net debt: designated as hedges		99
Derivatives and embedded derivatives not related to net debt: not designated as hedges		168
Total financial assets		1,482
IAS 39 [Member] | Held to maturity assets [member]
Disclosure of financial assets [Line Items]
Other investments, including loans		12
Total financial assets		$ 12

Financial instruments and ris_4

Financial instruments and risk management - Summary of financial liabilities by categories (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of financial liabilities [Line Items]
Trade and other financial payables	$ (5,552)	$ (5,922)
Short-term borrowings and bank overdrafts	(312)	(552)
Medium-term and long-term borrowings	(12,440)	(14,624)
IFRS 9 [member]
Disclosure of financial liabilities [Line Items]
Trade and other financial payables	(5,552)
Short-term borrowings and bank overdrafts	(312)
Medium-term and long-term borrowings	(12,440)
Derivatives related to net debt: designated as hedges	(358)
Derivatives and embedded derivatives not related to net debt: not designated as hedges	(98)
Embedded derivatives not related to net debt: designated as hedges	(46)
Other financial liabilities	(666)
Total financial liabilities	(19,472)
IFRS 9 [member] | Amortised Cost [member]
Disclosure of financial liabilities [Line Items]
Trade and other financial payables	(5,513)
Short-term borrowings and bank overdrafts	(312)
Medium-term and long-term borrowings	(12,440)
Other financial liabilities	(666)
Total financial liabilities	(18,931)
IFRS 9 [member] | Fair value through profit loss [member]
Disclosure of financial liabilities [Line Items]
Trade and other financial payables	(39)
Derivatives related to net debt: designated as hedges	(358)
Derivatives and embedded derivatives not related to net debt: not designated as hedges	(98)
Embedded derivatives not related to net debt: designated as hedges	(46)
Total financial liabilities	$ (541)
IAS 39 [Member]
Disclosure of financial liabilities [Line Items]
Trade and other financial payables		(5,922)
Short-term borrowings and bank overdrafts		(552)
Medium-term and long-term borrowings		(14,624)
Derivatives related to net debt: designated as hedges		(276)
Other derivatives and embedded derivatives: not designated as hedges		(255)
Other financial liabilities		(345)
Total financial liabilities		(21,974)
IAS 39 [Member] | Held at fair value [member]
Disclosure of financial liabilities [Line Items]
Trade and other financial payables		(15)
Derivatives related to net debt: designated as hedges		(276)
Other derivatives and embedded derivatives: not designated as hedges		(255)
Total financial liabilities		(546)
IAS 39 [Member] | Other financial liability held to maturity [Member]
Disclosure of financial liabilities [Line Items]
Trade and other financial payables		(5,907)
Short-term borrowings and bank overdrafts		(552)
Medium-term and long-term borrowings		(14,624)
Other financial liabilities		(345)
Total financial liabilities		$ (21,428)

Financial instruments and ris_5

Financial instruments and risk management - Summary of financial assets by categories (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Assets [Abstract]
Highly liquid financial assets held in managed investment funds classified as held for trading	$ 2,522	$ 958

Financial instruments and ris_6

Financial instruments and risk management - Additional information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Abstract]
Description of exposure to risk	Rio Tinto’s policies on financial risk management are defined such that the Group has a capital structure in place to manage the organisation through the commodity cycle and that Group’s exposures may float with the market. Any exceptions to this general principle are formally approved. The Group is exposed to capital, liquidity, commodity price, credit, foreign exchange and interest rate risk.
Transfers between Level 1 and Level 2	$ 0	$ 0
Transfers between Level 2 and Level 3	$ 0	$ 0

Financial instruments and ris_7

Financial instruments and risk management - Capital and liquidity risk management - Additional information (Detail) - USD ($) $ in Millions	4 Months Ended	12 Months Ended
	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Financial Instruments [Line Items]
Net debt		$ (255)	$ 3,845	$ 9,587
Net cash		11,821	13,884	8,465
Buy-back of bonds	$ 1,900		2,500	$ 7,500
Borrowings		$ 12,752	15,176
Percentage of change in spot price		15.00%
Level 1 [member]
Disclosure Of Financial Instruments [Line Items]
Borrowings		$ 7,500	9,600
Borrowings at fair value		8,300	10,900
Level 3 [member]
Disclosure Of Financial Instruments [Line Items]
Borrowings		4,200	4,100
Borrowings at fair value		$ 4,600	4,700
Percentage of increase in copper price		10.00%
Period of London metal exchange curve		ten-year
Decrease in carrying value of forward contract due to long-term metal pricing assumptions		$ 22	41
Increase in carrying value of forward contract due to long-term metal pricing assumptions		$ 14	22
Percentage of change in coal spot price		15.00%
Increase in carrying value of forward contract due to coal spot price assumptions		$ 181
Decrease in carrying value of forward contract due to decrease in spot price		95
Capital and liquidity risk management [member]
Disclosure Of Financial Instruments [Line Items]
Net debt		(255)	$ 3,845
Net cash		$ 300
Net debt to total capital percentage		(1.00%)	7.00%
Description of interest coverage on debt		22 times	14 times
Revolving credit facilities period		1 year
Borrowing maturity		November 2,022
Description of rating agencies used		Standard & Poor’s and Moody’s investor services
Capital and liquidity risk management [member] | Rio Tinto Finance (USA) plc and Rio Tinto Finance (USA) Limited [member]
Disclosure Of Financial Instruments [Line Items]
Buy-back of bonds		$ 1,900	$ 2,500
Aggregate cash outflow before fees		2,000	$ 2,700
Capital and liquidity risk management [member] | November Two Thousand And Twenty One
Disclosure Of Financial Instruments [Line Items]
Revolving credit facilities		1,900
Capital and liquidity risk management [member] | November Two Thousand And Twenty Two
Disclosure Of Financial Instruments [Line Items]
Revolving credit facilities		$ 5,600
Bottom of range [Member] | Capital and liquidity risk management [member]
Disclosure Of Financial Instruments [Line Items]
Percentage of underlying earnings		40.00%
Top of range [Member] | Capital and liquidity risk management [member]
Disclosure Of Financial Instruments [Line Items]
Percentage of underlying earnings		60.00%

Financial instruments and ris_8

Financial instruments and risk management - Summary of capital and liquidity risk management (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about hedging instruments [Line Items]
Equity attributable to owners of Rio Tinto (see Group balance sheet)	$ 43,686	$ 44,542	$ 44,711	$ 39,290
Equity attributable to non-controlling interests (see Group balance sheet)	6,137		6,404
Net debt	(255)		3,845	$ 9,587
Capital and liquidity risk management [member]
Disclosure of detailed information about hedging instruments [Line Items]
Equity attributable to owners of Rio Tinto (see Group balance sheet)	43,686		44,711
Equity attributable to non-controlling interests (see Group balance sheet)	6,137		6,404
Net debt	(255)		3,845
Total capital	$ 49,568		$ 54,960

Financial instruments and ris_9

Financial instruments and risk management - Summary of credit ratings (Detail) - Capital and liquidity risk management [member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Long term rating [member]
Disclosure of external credit grades [Line Items]
Credit ratings	A/A3	A-/A3
Short term rating [member]
Disclosure of external credit grades [Line Items]
Credit ratings	A-1/P-2	A-1/P-2
Outlook [member]
Disclosure of external credit grades [Line Items]
Credit ratings	Stable/Stable	Positive/Stable

Financial instruments and ri_10

Financial instruments and risk management - Maturity analysis for non-derivative financial liabilities and derivative financial liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Trade and other financial payables	$ (5,552)	$ (5,922)
Borrowings before swaps	(12,917)	(15,297)
Expected future interest payments	(7,238)	(7,819)
Other financial liabilities	(666)	(345)
Derivatives related to net debt - net settled	(148)	88
– gross inflows	1,951	2,663
– gross outflows	(2,429)	(3,066)
Derivatives not related to net debt - net settled	(83)	(295)
– gross inflows	1,664	795
– gross outflows	(1,733)	(802)
Total	(27,151)	(30,000)
Due within 1 year [member]
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Trade and other financial payables	(5,129)	(5,488)
Borrowings before swaps	(312)	(552)
Expected future interest payments	(651)	(679)
Other financial liabilities	(666)	(302)
Derivatives related to net debt - net settled	(36)	10
– gross inflows	48	62
– gross outflows	(79)	(82)
Derivatives not related to net debt - net settled	(27)	(43)
– gross inflows	1,664	795
– gross outflows	(1,733)	(802)
Total	(6,921)	(7,081)
Between 1 and 2 years [member]
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Trade and other financial payables	(423)	(434)
Borrowings before swaps	(562)	(148)
Expected future interest payments	(653)	(673)
Other financial liabilities		(43)
Derivatives related to net debt - net settled	(36)	10
– gross inflows	508	62
– gross outflows	(595)	(82)
Derivatives not related to net debt - net settled	(13)	(36)
Total	(1,774)	(1,344)
Between 2 and 3 years [member]
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Borrowings before swaps	(166)	(1,011)
Expected future interest payments	(636)	(670)
Derivatives related to net debt - net settled	(36)	14
– gross inflows	39	958
– gross outflows	(58)	(1,051)
Derivatives not related to net debt - net settled	(5)	(33)
Total	(862)	(1,793)
Between 3 and 4 years [member]
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Borrowings before swaps	(660)	(916)
Expected future interest payments	(630)	(638)
Derivatives related to net debt - net settled	(36)	11
– gross inflows	39	44
– gross outflows	(58)	(55)
Derivatives not related to net debt - net settled	(5)	(24)
Total	(1,350)	(1,578)
Between 4 and 5 years [member]
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Borrowings before swaps	(741)	(1,283)
Expected future interest payments	(586)	(606)
Derivatives related to net debt - net settled	4	7
– gross inflows	39	44
– gross outflows	(58)	(55)
Derivatives not related to net debt - net settled	(5)	(21)
Total	(1,347)	(1,914)
More than 5 years [member]
Disclosure Of Maturity Analysis For Derivative Financial Liabilities [Line Items]
Borrowings before swaps	(10,476)	(11,387)
Expected future interest payments	(4,082)	(4,553)
Derivatives related to net debt - net settled	(8)	36
– gross inflows	1,278	1,493
– gross outflows	(1,581)	(1,741)
Derivatives not related to net debt - net settled	(28)	(138)
Total	$ (14,897)	$ (16,290)

Financial instruments and ri_11

Financial instruments and risk management - Commodity price risk - Additional information (Detail) - Commodity price risk [Member] lb in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)lb	Dec. 31, 2017USD ($)lb
Disclosure Of Financial Instruments [Line Items]
Description of hedging strategy	Rio Tinto’s exposure to commodity prices is diversified by virtue of its broad commodity base and the Group does not generally consider that commodity fixed price hedging would provide a long-term benefit to shareholders.
Copper [member]
Disclosure Of Financial Instruments [Line Items]
Quantity of unsettled copper sales | lb	240	250
Provisionally priced unsettled copper sales per pound	$ 277	$ 304
Increase (Decrease) in net earnings due to price change	$ 37	$ 41

Financial instruments and ri_12

Financial instruments and risk management - Summary of notional aluminium forward sales contracts embedded in power contracts (Detail) $ in Millions	Dec. 31, 2018USD ($)Tonne
Due within 1 year [member]
Disclosure Of Financial Instruments [Line Items]
Notional amount (in tonnes) | Tonne	56,481
Notional amount | $	$ 114
Average hedged rate (in US$ per tonne)	2,013
Between 1 and 5 years [Member]
Disclosure Of Financial Instruments [Line Items]
Notional amount (in tonnes) | Tonne	286,666
Notional amount | $	$ 634
Average hedged rate (in US$ per tonne)	2,210
Between 5 and 10 years [Member]
Disclosure Of Financial Instruments [Line Items]
Notional amount (in tonnes) | Tonne	358,416
Notional amount | $	$ 870
Average hedged rate (in US$ per tonne)	2,426
After 10 years [Member]
Disclosure Of Financial Instruments [Line Items]
Notional amount (in tonnes) | Tonne	65,548
Notional amount | $	$ 168
Average hedged rate (in US$ per tonne)	2,562

Financial instruments and ri_13

Financial instruments and risk management - Summary of impact of hedging instrument on statement of financial position (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Aluminium embedded derivatives separated from the power contract [Member]
Disclosure Of Financial Instruments [Line Items]
Notional amount	$ 1,786
Carrying value	8
Change in fair value used for measuring ineffectiveness for the period	205
Aluminium embedded derivatives separated from the power contract [Member] | Othe financial assets [Member]
Disclosure Of Financial Instruments [Line Items]
Line item in the statement of financial position	54
Aluminium embedded derivatives separated from the power contract [Member] | Other financial liability [Member]
Disclosure Of Financial Instruments [Line Items]
Line item in the statement of financial position	46
Highly Probable Forecast Aluminum Sales
Disclosure Of Financial Instruments [Line Items]
Change in fair value used for measuring ineffectiveness for the period	(182)
Cash flow hedge reserve US$m	$ 179

Financial instruments and ri_14

Financial instruments and risk management - Summary of effect of the cash flow hedge in statement of profit or loss and other comprehensive income (OCI) (Detail) - Cash flow hedge reserve [member] - Highly Probable Forecast Aluminum Sales $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Disclosure Of Financial Instruments [Line Items]
Total hedging gain recognised in OCI US$m	$ 181
Ineffectiveness recognised in profit or loss US$m	24
Amount reclassified from OCI to profit or loss US$m	$ 2
Net operating costs [Member]
Disclosure Of Financial Instruments [Line Items]
Line item in the statement of profit or loss	Net operating costs (raw materials, consumables, repairs and maintenance)
Consolidated sales revenue [Member]
Disclosure Of Financial Instruments [Line Items]
Line item in the statement of profit or loss	Consolidated sales revenue

Financial instruments and ri_15

Financial instruments and risk management - Summary of changes in market price relevant to alumina purchase price swaps outstanding (Detail) - Commodity price risk [Member] - Aluminium [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Effect on net earnings [Member]
Disclosure Of Financial Instruments [Line Items]
Percentage increase in market price change	10.00%
Percentage decrease in market price change	(10.00%)
Decrease in market price change of commodities	$ (102)	$ (203)
Increase in market price change of commodities	$ 35	$ 212
Effect on equity [Member]
Disclosure Of Financial Instruments [Line Items]
Percentage increase in market price change	10.00%
Percentage decrease in market price change	(10.00%)
Decrease in market price change of commodities	$ (101)
Increase in market price change of commodities	$ 103

Financial instruments and ri_16

Financial instruments and risk management - Credit risk - Additional information (Detail) - Credit risk [Member] - Customer	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]
Description of customers receivable owing	The Group had approximately 113 customers (2017: 115 customers) that owed the Group more than US$5 million each and these balances accounted for approximately 84% (2017: 78%) of all trade receivables. There were 17 customers (2017: 23 customers) with balances greater than US$20 million accounting for just over 34% (2017: 35%) of all trade receivables.
More than US dollar 5 million [member]
Disclosure Of Financial Instruments [Line Items]
Number of customers	113	115
Per cent of trade receivables	84.00%	78.00%
Greater than US dollar 20 million [member]
Disclosure Of Financial Instruments [Line Items]
Number of customers	17	23
Per cent of trade receivables	34.00%	35.00%

Financial instruments and ri_17

Financial instruments and risk management - Summary of maximum credit risk exposure of the Group's financial assets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Trade and other financial receivables [member]
Disclosure Of Credit Risk Exposure [Line Items]
Maximum credit risk exposure	$ 3,007	$ 2,985
Credit risk [Member]
Disclosure Of Credit Risk Exposure [Line Items]
Maximum credit risk exposure	17,156	14,993
Credit risk [Member] | Cash and cash equivalents [member]
Disclosure Of Credit Risk Exposure [Line Items]
Maximum credit risk exposure	10,773	10,550
Credit risk [Member] | Derivative assets [member]
Disclosure Of Credit Risk Exposure [Line Items]
Maximum credit risk exposure	556	267
Credit risk [Member] | Loans to equity accounted units [member]
Disclosure Of Credit Risk Exposure [Line Items]
Maximum credit risk exposure	38	39
Credit risk [Member] | Fair value [member] | Loans And Receivables [Member] | Held to maturity assets [member] | Investments [member]
Disclosure Of Credit Risk Exposure [Line Items]
Maximum credit risk exposure	$ 2,782	$ 1,152

Financial instruments and ri_18

Financial instruments and risk management - Summary by currency, Group's net debt, after taking into account relevant cross currency interest rate swaps and foreign exchange contracts (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	$ (12,752)	$ (15,176)
Cash and cash equivalents	10,773	10,550
Net cash/(debt)	255	(3,845)	$ (9,587)
Foreign exchange risk [member]
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	(12,751)
Derivatives related to net debt: designated as hedges	(288)
Cash and cash equivalents	10,772
Other investments	2,522
Net cash/(debt)	255	(3,845)
Foreign exchange risk [member] | US Dollars [Member]
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	(12,080)
Derivatives related to net debt: designated as hedges	(288)
Cash and cash equivalents	10,310
Other investments	2,522
Net cash/(debt)	464	(3,628)
Foreign exchange risk [member] | Australian dollar [Member]
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	(472)
Cash and cash equivalents	217
Net cash/(debt)	(255)	(208)
Foreign exchange risk [member] | Euro [Member]
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	(39)
Cash and cash equivalents	17
Net cash/(debt)	(22)	(58)
Foreign exchange risk [member] | South African rand [Member]
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	95
Net cash/(debt)	95	59
Foreign exchange risk [member] | Canadian dollar [Member]
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	(157)
Cash and cash equivalents	23
Net cash/(debt)	(134)	(148)
Foreign exchange risk [member] | Other currencies [member]
Disclosure Of Financial Instruments [Line Items]
Total borrowings excluding overdrafts	(3)
Cash and cash equivalents	110
Net cash/(debt)	$ 107	$ 138

Financial instruments and ri_19

Financial instruments and risk management - Foreign exchange risk - Additional information (Detail) - Foreign exchange risk [member]	12 Months Ended
	Dec. 31, 2018
Disclosure Of Financial Instruments [Line Items]
Description of hedging strategy	Under normal market conditions, the Group does not consider that active currency hedging of transactions would provide long-term benefits to shareholders. The Group reviews its exposure on a regular basis and will undertake hedging if deemed appropriate. Currency protection measures may be deemed appropriate in specific commercial circumstances. Capital expenditures and other significant financial items such as acquisitions, disposals, tax and dividend cash flows may be hedged subject to strict limits laid down by the board. Refer to section B for details of the cross-currency interest rate swaps, and the currency forward and option contracts used to manage the currency risk exposures
Description of sensitivity analysis	Estimated retranslation effect on financial assets and financial liabilities, including intragroup balances, of a 10% strengthening in the closing exchange rate of the US dollar against significant currencies. 10% is the annual exchange rate movement that management deems to be reasonably probable (on an annual basis over the long run) for one of the Group’s significant currencies and as such provides an appropriate representation. Sensitivities are calculated in the functional currencies of individual Group entities. The impact of these on net earnings and underlying earnings is translated into US dollars at the year-end exchange rates present in note 41. The sensitivity associated with a 10% weakening of a particular currency would be broadly equal and opposite within equity to the figures presented below. The impact is expressed in terms of the effect on net earnings, underlying earnings and equity, assuming that each exchange rate moves in isolation.
Percentage of change in annual foreign exchange rate	10.00%

Financial instruments and ri_20

Financial instruments and risk management - Gains or Losses Associated with Ten Percent Strengthening of US Dollar (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Disclosure of detailed information about hedging instruments [Line Items]
Effect on net earnings	$ 56,000,000	$ (61,000,000)	$ (38,000,000)
Australian dollar [Member]
Disclosure of detailed information about hedging instruments [Line Items]
Closing exchange rate	0.70	0.78	0.72
Canadian dollar [Member]
Disclosure of detailed information about hedging instruments [Line Items]
Closing exchange rate	0.73	0.79	0.74
Euro Member Countries, Euro
Disclosure of detailed information about hedging instruments [Line Items]
Closing exchange rate	1.14	1.20	1.05
Foreign exchange risk [member] | Australian dollar [Member]
Disclosure of detailed information about hedging instruments [Line Items]
Closing exchange rate	0.70	0.78
Effect on net earnings	$ 346,000,000	$ 608,000,000
Amount impacting underlying earnings	1,000,000	47,000,000
Foreign Exchange Gain Loss Amount Impact Directly On Equity	$ (993,000,000)	$ (1,657,000,000)
Foreign exchange risk [member] | Canadian dollar [Member]
Disclosure of detailed information about hedging instruments [Line Items]
Closing exchange rate	0.73	0.79
Effect on net earnings	$ (82,000,000)	$ (134,000,000)
Amount impacting underlying earnings	$ 7,000,000	$ 3,000,000
Foreign exchange risk [member] | Euro Member Countries, Euro
Disclosure of detailed information about hedging instruments [Line Items]
Closing exchange rate	1.14	1.20
Effect on net earnings	$ 202,000,000	$ 165,000,000
Amount impacting underlying earnings	$ 5,000,000	$ (2,000,000)

Financial instruments and ri_21

Financial instruments and risk management - Interest rate risk - Additional information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Interest rate swaps [member] | US Dollars [Member]
Disclosure Of Financial Instruments [Line Items]
Notional amount	$ 4,300,000,000	$ 5,700,000,000
Interest rate risk [Member]
Disclosure Of Financial Instruments [Line Items]
Adjusted total borrowings	$ 10,200,000,000	$ 12,500,000,000
Weighted average maturity period	11 years	ten years
Description of borrowings, interest rate basis	the effect on net earnings of a 100 basis point increase in US dollar LIBOR interest rates, with all other variables held constant, would be an income of US$8 million (2017: charge of US$8 million) due to the net cash position in 2018 versus the net debt position in 2017. The Group has an exposure to interest rate volatility within shareholders’ equity arising from fair value movements on derivatives in the cash flow hedge reserve. These derivatives have an underlying exposure to sterling and US dollars. With all factors remaining constant, and based on the composition of derivatives impacting the cash flow reserve at 31 December 2018, the sensitivity of a 100 basis point increase in interest rates in each of the currencies in isolation would impact equity, before tax, by a charge of US$69 million (2017: US$84 million charge) for sterling and a credit of US$78 million (2017: US$88 million credit) for US dollars. A 100 basis point decrease would have broadly the same impact in the opposite direction. These balances will not remain constant throughout 2019, and therefore this information should be used with care.
Interest rate risk [Member] | United Kingdom, Pounds
Disclosure Of Financial Instruments [Line Items]
Increase in financial derivative charges on interest rate before tax	$ 69,000,000	$ 84,000,000
Interest rate risk [Member] | US Dollars [Member]
Disclosure Of Financial Instruments [Line Items]
Increase in financial derivative charges on interest rate before tax	$ 78,000,000	$ 88,000,000
Interest rate risk [Member] | Floating interest rate [Member]
Disclosure Of Financial Instruments [Line Items]
Adjusted borrowings, interest rate	79.00%	82.00%
Interest rate risk [Member] | Fixed interest rate [Member]
Disclosure Of Financial Instruments [Line Items]
Adjusted borrowings, interest rate	21.00%	18.00%
Interest rate risk [Member] | LIBOR [member]
Disclosure Of Financial Instruments [Line Items]
Borrowings, interest rate basis	1.00%
Borrowing cost recognised	$ (8,000,000)	$ 8,000,000
Interest rate risk [Member] | Interest rate swaps [member]
Disclosure Of Financial Instruments [Line Items]
Description of hedging strategy	The Group hedges its interest rate risk by entering into interest rate derivatives to achieve its policies. The Group reviews the positions on a regular basis. During 2018, in conjunction with its liability management programme
Notional amount	$ 1,900,000,000	2,000,000,000
Inflows of cash from liability management programme	40,000,000	5,000,000
Accrued interest	$ 11,000,000	$ 2,000,000

Financial instruments and ri_22

Financial instruments and risk management - Summary of derivative financial instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]
Total net derivative instruments	$ 54	$ (264)
Derivative financial assets	556	267
Derivative financial liabilities	(502)	(531)
Non-current derivative financial instruments	468	238
Current derivative financial instruments	88	29
Current liabilities	(95)	(50)
Non-current liabilities	(407)	(481)
Total net derivative instruments	54	(264)
Derivatives designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	124	99
Derivative financial liabilities	(404)	(276)
Derivatives not designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	432	168
Derivative financial liabilities	(98)	(255)
Interest rate swaps [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	70	99
Interest rate swaps [member] | Derivatives designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	70	99
Derivative financial liabilities	(137)	(127)
Cross currency interest rate swaps [member] | Derivatives designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial liabilities	(221)	(149)
Aluminium Embedded Derivatives | Derivatives designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	54
Derivative financial liabilities	(46)
Aluminium Embedded Derivatives | Derivatives not designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	346	140
Derivative financial liabilities		(238)
Currency Forward Contracts Options And Swaps | Derivatives not designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets		7
Derivative financial liabilities	(68)	(2)
Aluminium forward contracts [member] | Derivatives not designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	26	21
Derivative financial liabilities	(19)	(9)
Other embedded derivatives [member] | Derivatives not designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	6
Derivative financial liabilities		(5)
Other commodity contracts [member] | Derivatives not designated as hedges [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	54
Derivative financial liabilities	(11)	(1)
Due within 1 year [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	88	29
Derivative financial liabilities	(95)	(50)
Between 1 and 5 years [Member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	153	31
Derivative financial liabilities	(205)	(233)
More than 5 years [member]
Disclosure Of Financial Instruments [Line Items]
Derivative financial assets	315	207
Derivative financial liabilities	$ (202)	$ (248)

Financial instruments and ri_23

Financial instruments and risk management - Summary of fair value of financial instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Abstract]
Short term borrowings, carrying value	$ (312)	$ (552)
Medium and long term borrowings, carrying value	(12,440)	(14,624)
Short term borrowings, fair value	(312)	(552)
Medium and long term borrowings, fair value	$ (13,554)	$ (16,385)

Financial instruments and ri_24

Financial instruments and risk management - Summary of financial instruments carried at fair value (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	$ 10,773	$ 10,550
Investments in equity shares and funds	130
Equity shares and quoted funds	130	136
Other investments, including loans	2,782	1,152
Trade and other financial receivables	3,007	2,985
Financial assets (excluding derivative assets)	16,692	14,823
Forward contracts and option contracts: designated as hedges(f) (Section B)	8
Forward contracts and option contracts, not designated as hedges	334	(87)
Derivatives related to net debt	(288)	(177)
Trade and other financial payables	(5,552)	(5,922)
Total	11,194	8,637
Fair value [member] | Level 1 [member]
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	7,994
Investments in equity shares and funds	92
Equity shares and quoted funds		88
Other investments, including loans	2,544	1,037
Trade and other financial receivables	20
Financial assets (excluding derivative assets)	10,650	1,125
Total	10,650	1,125
Fair value [member] | Level 2 [member]
Disclosure Of Financial Instruments [Line Items]
Trade and other financial receivables	972	90
Financial assets (excluding derivative assets)	972	90
Forward contracts and option contracts, not designated as hedges	(25)	11
Derivatives related to net debt	(288)	(177)
Trade and other financial payables	(39)	(15)
Total	620	(91)
Fair value [member] | Level 3 [member]
Disclosure Of Financial Instruments [Line Items]
Investments in equity shares and funds	38
Equity shares and quoted funds		3
Other investments, including loans	232	88
Financial assets (excluding derivative assets)	270	91
Forward contracts and option contracts: designated as hedges(f) (Section B)	8
Forward contracts and option contracts, not designated as hedges	359	(98)
Total	637	(7)
Not held at fair value [member]
Disclosure Of Financial Instruments [Line Items]
Cash and cash equivalents	2,779	10,550
Equity shares and quoted funds		45
Other investments, including loans	6	27
Trade and other financial receivables	2,015	2,895
Financial assets (excluding derivative assets)	4,800	13,517
Trade and other financial payables	(5,513)	(5,907)
Total	$ (713)	$ 7,610

Financial instruments and ri_25

Financial instruments and risk management - Summary of financial instruments carried at fair value (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]
Provisionally priced receivables recognised relating to sales contracts	$ 889,000,000	$ 90,000,000
Aluminium embedded derivatives separated from the power contract [Member] | Level 3 [member]
Disclosure Of Financial Instruments [Line Items]
Long-term embedded derivatives expiry term	Level 3 derivatives consist of derivatives embedded in electricity purchase contracts linked to the LME with terms expiring between 2025 and 2030 (2017: 2018 and 2030).
Long-term embedded derivatives with fair value	$ 338,000,000	(98,000,000)
Aluminium forward contracts [member]
Disclosure Of Financial Instruments [Line Items]
Range of market price	In valuing these derivatives, aluminium prices are flatlined beyond the market forward curve and increased by projected inflation up to the date of expiry of each contract. Future market premiums are estimated based on historical trends. The range of market prices are US$2,426 per metric tonne in 2029 to US$2,507 in 2030 (2017: US$2,679 per metric tonne in 2028 to US$2,848 in 2030).
Aluminium forward contracts [member] | Bottom of range [Member]
Disclosure Of Financial Instruments [Line Items]
Fair value of derivative commodity price per metric tonne	$ 2,426	2,679
Aluminium forward contracts [member] | Top of range [Member]
Disclosure Of Financial Instruments [Line Items]
Fair value of derivative commodity price per metric tonne	$ 2,507	$ 2,848

Financial instruments and ri_26

Financial instruments and risk management - Summary of changes in fair value of Level 3 financial assets and financial liabilities (Detail) - Level 3 [member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]
Opening balance	$ (7)	$ 479
Adjustment from transition to IFRS 9	19
Currency translation adjustments	(23)	8
– consolidated sales revenue		1
– net operating costs	9	(5)
- consolidated sales revenue		17
– net operating costs	375	(508)
Total unrealised gains transferred into other comprehensive income through cash flow hedges	181
Additions	67
Disposals/maturity of financial instruments	(6)	(5)
Transfers	22	6
Closing balance	637	(7)
Total gains/(losses) for the year included in the income statement for assets and liabilities held at year end	$ 346	$ (491)

Contingencies and commitments -

Contingencies and commitments - Summary of capital commitments (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Capital Commitments
Capital Commitments	$ 2,283	$ 2,641
Due within 1 year [member]
Capital Commitments
Capital Commitments	1,742	2,052
Between 1 and 3 years [member]
Capital Commitments
Capital Commitments	439	531
Between 3 and 5 years [member]
Capital Commitments
Capital Commitments	66	58
More than 5 years [member]
Capital Commitments
Capital Commitments	36
Joint ventures [Member]
Capital Commitments
Capital Commitments	116	29
Joint ventures [Member] | Due within 1 year [member]
Capital Commitments
Capital Commitments	115	$ 29
Joint ventures [Member] | Between 1 and 3 years [member]
Capital Commitments
Capital Commitments	$ 1

Contingencies and commitments_2

Contingencies and commitments - Additional information (Detail) £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2017GBP (£)
Disclosure of commitments and contingencies [Line Items]
Contractual capital commitments	$ 400	$ 500
Borrowings	$ 12,752	15,176
Turquoise Hill Resources Ltd (including Oyu Tolgoi LLC) [member]
Disclosure of commitments and contingencies [Line Items]
Ownership percentage in subsidiary	51.00%
Company of operation, Subsidiary	Turquoise Hill Resources Ltd
Oyu Tolgoi LLC [member]
Disclosure of commitments and contingencies [Line Items]
Borrowings	$ 4,300	4,300
Erdenes Oyu Tolgoi LLC [member]
Disclosure of commitments and contingencies [Line Items]
Percentage of ownership interest exchanged in joint venture	34.00%
Company of operation	Oyu Tolgoi LLC
Turquoise Hill Resources Ltd [member]
Disclosure of commitments and contingencies [Line Items]
Percentage of ownership interest exchanged in joint venture	66.00%
Company of operation	Oyu Tolgoi LLC
Contingent liabilities related to joint ventures [Member]
Disclosure of commitments and contingencies [Line Items]
Ownership percentage in subsidiary	100.00%
United Kingdoms Financial Conduct Authority (FCA) [Member]
Disclosure of commitments and contingencies [Line Items]
Financial penalty		36.4	£ 27.4
Minera Escondida Limitada [member]
Disclosure of commitments and contingencies [Line Items]
Minera Escondida Limitada undrawn shareholder line of credit Rio Tinto share	$ 225	$ 225
Percentage of ownership interest exchanged in joint venture	30.00%	30.00%	30.00%
Company of operation	Minera Escondida Limitada
Rio Tinto Finance (USA) Limited and Rio Tinto Finance (USA) plc [member] | Contingent liabilities related to joint ventures [Member] | Financial guarantee contracts [Member]
Disclosure of commitments and contingencies [Line Items]
Amounts guaranteed by parent companies	$ 7,500	$ 7,500
Rio Tinto Finance (USA) Limited and Rio Tinto Finance (USA) plc [member] | Contingent liabilities related to joint ventures [Member] | Financial guarantee contracts [Member] | Bonds [member]
Disclosure of commitments and contingencies [Line Items]
Amounts guaranteed by parent companies	4,400	5,800
Rio Tinto Finance (USA) Limited and Rio Tinto Finance (USA) plc [member] | Contingent liabilities related to joint ventures [Member] | Financial guarantee contracts [Member] | Bonds [member]
Disclosure of commitments and contingencies [Line Items]
Amounts guaranteed by parent companies	$ 1,600	$ 2,100

Contingencies and commitments_3

Contingencies and commitments - Summary of aggregate amount of minimum lease payments under non-cancellable operating leases (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure of finance lease and operating lease by lessee [Line Items]
Aggregate amount of minimum lease payments under non-cancellable operating leases	$ 1,717	$ 1,845
Due within 1 year [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Aggregate amount of minimum lease payments under non-cancellable operating leases	475	397
Between 1 and 3 years [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Aggregate amount of minimum lease payments under non-cancellable operating leases	587	542
Between 3 and 5 years [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Aggregate amount of minimum lease payments under non-cancellable operating leases	270	313
More than 5 years [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Aggregate amount of minimum lease payments under non-cancellable operating leases	$ 385	$ 593

Contingencies and commitments_4

Contingencies and commitments - Summary of aggregate amount of future payment commitments under purchase obligations outstanding (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	$ 17,050	$ 19,480
Due within 1 year [member]
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	2,804	2,874
Between 1 and 2 years [member]
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	1,565	1,712
Between 2 and 3 years [member]
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	1,344	1,401
Between 3 and 4 years [member]
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	1,097	1,282
Between 4 and 5 years [member]
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	882	1,026
More than 5 years [member]
Disclosure of future payment commitments under purchase obligations [Line Items]
Aggregate amount of future payment commitments under purchase obligations outstanding	$ 9,358	$ 11,185

Contingencies and commitments_5

Contingencies and commitments - Summary of aggregate amount of future payment commitments under purchase obligations outstanding (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Future Payment Commitments Under Purchase Obligations [Abstract]
Reduction In Future Payment Commitments	$ 309

Contingencies and commitments_6

Contingencies and commitments - Summary of subsidiaries and joint operations contingent liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Contingent Liabilities [Abstract]
Indemnities and other performance guarantees	$ 317	$ 552

Average number of employees - S

Average number of employees - Summary of average number of employees (Detail) - Employee	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of average number of employees [Line Items]
Average number of employees	47,458	46,807	51,029
Investment in equity accounted units [member]
Disclosure of average number of employees [Line Items]
Average number of employees	3,129	3,108	3,507
Australia and New Zealand [member]
Disclosure of average number of employees [Line Items]
Average number of employees	19,595	19,643	21,338
Australia and New Zealand [member] | Investment in equity accounted units [member]
Disclosure of average number of employees [Line Items]
Average number of employees	578	602	849
Canada [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	10,620	10,256	10,239
United Kingdom [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	287	309	487
Europe [member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,418	1,505	1,722
Africa [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	4,758	4,730	6,145
Africa [Member] | Investment in equity accounted units [member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,262	1,269	1,270
United States [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	3,792	3,429	3,196
Mongolia [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	2,886	2,861	2,737
Indonesia [member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,615	1,642	2,862
South America [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,499	1,434	1,554
South America [Member] | Investment in equity accounted units [member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,289	1,237	1,388
Other countries [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	988	998	749
Subsidiaries And Joint Operations [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	44,329	43,699	47,522
Subsidiaries And Joint Operations [Member] | Australia and New Zealand [member]
Disclosure of average number of employees [Line Items]
Average number of employees	19,017	19,041	20,489
Subsidiaries And Joint Operations [Member] | Canada [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	10,620	10,256	10,239
Subsidiaries And Joint Operations [Member] | United Kingdom [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	287	309	487
Subsidiaries And Joint Operations [Member] | Europe [member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,418	1,505	1,722
Subsidiaries And Joint Operations [Member] | Africa [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	3,496	3,461	4,875
Subsidiaries And Joint Operations [Member] | United States [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	3,792	3,429	3,196
Subsidiaries And Joint Operations [Member] | Mongolia [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	2,886	2,861	2,737
Subsidiaries And Joint Operations [Member] | Indonesia [member]
Disclosure of average number of employees [Line Items]
Average number of employees	1,615	1,642	2,862
Subsidiaries And Joint Operations [Member] | South America [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	210	197	166
Subsidiaries And Joint Operations [Member] | Other countries [Member]
Disclosure of average number of employees [Line Items]
Average number of employees	988	998	749

Average number of employees -_2

Average number of employees - Summary of average number of employees (Parenthetical) (Detail) - Employee	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of average number of employees [Line Items]
Average number of employees	47,458	46,807	51,029
Singapore [member]
Disclosure of average number of employees [Line Items]
Average number of employees	422	434	262
India [member]
Disclosure of average number of employees [Line Items]
Average number of employees	288	310	280

Average number of employees - A

Average number of employees - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018
Number And Average Number Of Employees [Abstract]
Per cent of employees of subsidiary companies	100.00%

Principal subsidiaries - Summar

Principal subsidiaries - Summary of principal in subsidiaries (Detail)	12 Months Ended
	Dec. 31, 2018
Argyle Diamonds Limited [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	100.00%
Argyle Diamonds Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	Argyle Diamonds Limited
Principal activities, Subsidiary	Mining and processing of diamonds
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Dampier Salt Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	Dampier Salt Limited
Principal activities, Subsidiary	Salt and gypsum
Proportion of class held (%), Subsidiary	68.36%
Ownership percentage in subsidiary	68.36%
Non-controlling interest (%), Subsidiary	31.64%
Energy Resources of Australia Limited [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	68.40%
Energy Resources of Australia Limited [Member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	Energy Resources of Australia Limited
Principal activities, Subsidiary	Uranium mining
Proportion of class held (%), Subsidiary	68.39%
Ownership percentage in subsidiary	68.39%
Non-controlling interest (%), Subsidiary	31.61%
Hamersley Iron Pty Limited [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	100.00%
Hamersley Iron Pty Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	Hamersley Iron Pty Limited
Principal activities, Subsidiary	Iron ore mining
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
North Mining Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	North Mining Limited
Principal activities, Subsidiary	Iron ore mining
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Queensland Coal Pty Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Subsidiary name	Queensland Coal Pty Limited
Principal activities, Subsidiary	Coal mining
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Rio Tinto Aluminium (Holdings) Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	Rio Tinto Aluminium (Holdings) Limited
Principal activities, Subsidiary	Bauxite mining; alumina production; primary aluminium smelting
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Robe River Mining Co Pty Ltd [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Australia
Subsidiary name	Robe River Mining Co Pty Ltd
Principal activities, Subsidiary	Iron ore mining
Ownership percentage in subsidiary	60.00%
Non-controlling interest (%), Subsidiary	40.00%
Robe River Mining Co Pty Ltd [member] | Class A shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Proportion of class held (%), Subsidiary	40.00%
Robe River Mining Co Pty Ltd [member] | Class B shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Proportion of class held (%), Subsidiary	76.36%
Alcan Alumina Ltda. [member] | Quota shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Brazil
Subsidiary name	Alcan Alumina Ltda.
Principal activities, Subsidiary	Alumina production and bauxite mining
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Iron Ore Company of Canada [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Canada
Subsidiary name	Iron Ore Company of Canada
Principal activities, Subsidiary	Iron ore mining; iron ore pellets
Proportion of class held (%), Subsidiary	58.72%
Ownership percentage in subsidiary	58.72%
Non-controlling interest (%), Subsidiary	41.28%
Rio Tinto Fer et Titane Inc. [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	100.00%
Rio Tinto Fer et Titane Inc. [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Canada
Subsidiary name	Rio Tinto Fer et Titane Inc.
Principal activities, Subsidiary	Titanium dioxide feedstock; high purity iron and steel
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Rio Tinto Fer et Titane Inc. [member] | Class B preference shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Canada
Subsidiary name	Rio Tinto Fer et Titane Inc.
Principal activities, Subsidiary	Titanium dioxide feedstock; high purity iron and steel
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Rio Tinto Fer et Titane Inc. [member] | Preferred shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Canada
Subsidiary name	Rio Tinto Fer et Titane Inc.
Principal activities, Subsidiary	Titanium dioxide feedstock; high purity iron and steel
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Diavik Diamond Mines (2012) Inc. [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Canada
Subsidiary name	Diavik Diamond Mines (2012) Inc.
Principal activities, Subsidiary	Diamond mining and processing
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Rio Tinto Alcan Inc. [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Canada
Subsidiary name	Rio Tinto Alcan Inc.
Principal activities, Subsidiary	Bauxite mining; alumina refining; aluminium smelting
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
Simfer Jersey Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Guinea
Subsidiary name	Simfer Jersey Limited
Principal activities, Subsidiary	Iron ore project
Proportion of class held (%), Subsidiary	53.00%
Ownership percentage in subsidiary	53.00%
Non-controlling interest (%), Subsidiary	47.00%
QIT Madagascar Minerals SA [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	80.00%
QIT Madagascar Minerals SA [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Madagascar
Subsidiary name	QIT Madagascar Minerals SA
Principal activities, Subsidiary	Ilmenite mining
Proportion of class held (%), Subsidiary	80.00%
Ownership percentage in subsidiary	80.00%
QIT Madagascar Minerals SA [member] | Common Shares and Investment Certificates [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Non-controlling interest (%), Subsidiary	15.00%
QIT Madagascar Minerals SA [member] | Investment certificates [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Madagascar
Subsidiary name	QIT Madagascar Minerals SA
Principal activities, Subsidiary	Ilmenite mining
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
QIT Madagascar Minerals SA [member] | Voting certificates [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Madagascar
Subsidiary name	QIT Madagascar Minerals SA
Principal activities, Subsidiary	Ilmenite mining
Proportion of class held (%), Subsidiary	80.00%
Ownership percentage in subsidiary	80.00%
Non-controlling interest (%), Subsidiary	20.00%
Turquoise Hill Resources Ltd (including Oyu Tolgoi LLC) [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Subsidiary name	Turquoise Hill Resources Ltd
Ownership percentage in subsidiary	51.00%
Turquoise Hill Resources Ltd (including Oyu Tolgoi LLC) [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Mongolia
Subsidiary name	Turquoise Hill Resources Ltd (including Oyu Tolgoi LLC)
Principal activities, Subsidiary	Copper and gold mining
Proportion of class held (%), Subsidiary	50.79%
Ownership percentage in subsidiary	50.79%
Non-controlling interest (%), Subsidiary	49.21%
Rossing Uranium [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	68.60%
Rossing Uranium [member] | B class of shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Namibia
Subsidiary name	Rössing Uranium Limited
Principal activities, Subsidiary	Uranium mining
Proportion of class held (%), Subsidiary	71.22%
Ownership percentage in subsidiary	68.62%
Non-controlling interest (%), Subsidiary	31.38%
Rossing Uranium [member] | C class of shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	Namibia
Subsidiary name	Rössing Uranium Limited
Principal activities, Subsidiary	Uranium mining
Proportion of class held (%), Subsidiary	70.59%
Richards Bay Titanium (Proprietary) Limited [member] | B ordinary shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	South Africa
Subsidiary name	Richards Bay Titanium (Proprietary) Limited
Principal activities, Subsidiary	Titanium dioxide;high purity iron production
Proportion of class held (%), Subsidiary	100.00%
Richards Bay Titanium (Proprietary) Limited [member] | B preference shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	South Africa
Subsidiary name	Richards Bay Titanium (Proprietary) Limited
Principal activities, Subsidiary	Titanium dioxide/high purity iron production
Proportion of class held (%), Subsidiary	100.00%
Richards Bay Titanium (Proprietary) Limited [member] | Parent preference shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	South Africa
Subsidiary name	Richards Bay Titanium (Proprietary) Limited
Principal activities, Subsidiary	Titanium dioxide/high purity iron production
Proportion of class held (%), Subsidiary	100.00%
Richards Bay Titanium (Proprietary) Limited [member] | B Ordinary, B Preference and Parent Preference Shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	74.00%
Non-controlling interest (%), Subsidiary	26.00%
Richards Bay Mining (Proprietary) Limited [member] | B ordinary shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	South Africa
Subsidiary name	Richards Bay Mining (Proprietary) Limited
Principal activities, Subsidiary	Ilmenite, rutile and zircon mining
Proportion of class held (%), Subsidiary	100.00%
Richards Bay Mining (Proprietary) Limited [member] | B preference shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	South Africa
Subsidiary name	Richards Bay Mining (Proprietary) Limited
Principal activities, Subsidiary	Ilmenite, rutile and zircon mining
Proportion of class held (%), Subsidiary	100.00%
Richards Bay Mining (Proprietary) Limited [member] | Parent preference shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	South Africa
Subsidiary name	Richards Bay Mining (Proprietary) Limited
Principal activities, Subsidiary	Ilmenite, rutile and zircon mining
Proportion of class held (%), Subsidiary	100.00%
Richards Bay Mining (Proprietary) Limited [member] | B Ordinary, B Preference and Parent Preference Shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary	74.00%
Non-controlling interest (%), Subsidiary	26.00%
Kennecott Holdings Corporation (including Kennecott Utah Copper, Kennecott Land and Kennecott Exploration) [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	United States of America
Subsidiary name	Kennecott Holdings Corporation (including Kennecott Utah Copper and Kennecott Exploration)
Principal activities, Subsidiary	Copper and gold mining, smelting and refining and exploration activities
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%
U.S. Borax Inc. [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Country of incorporation, Subsidiary	United States of America
Subsidiary name	U.S. Borax Inc.
Principal activities, Subsidiary	Mining, refining and marketing of borates
Proportion of class held (%), Subsidiary	100.00%
Ownership percentage in subsidiary	100.00%

Principal subsidiaries - Summ_2

Principal subsidiaries - Summary of principal in subsidiaries (Parenthetical) (Detail)	Aug. 01, 2018	Aug. 01, 2018	Dec. 31, 2018
Oyu Tolgoi LLC [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Indirect interest in subsidiary			33.50%
Robe river iron associates [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			65.00%
Non-controlling interest (%), Subsidiary			12.00%
Proportion of net beneficial interest			53.00%
Percentage of ownership interest exchanged in joint venture			65.00%
Hail Creek [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Percentage of ownership interest exchanged in joint venture		82.00%
Hail Creek [Member] | 2018 Disposals [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership interest in joint venture disposed	82.00%
Kestrel Underground Coal Mine [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Percentage of ownership interest exchanged in joint venture		80.00%
Kestrel Underground Coal Mine [Member] | 2018 Disposals [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership interest in joint venture disposed	80.00%
Consorcio De Aluminio Do Maranhao [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Percentage of ownership interest exchanged in joint venture			10.00%
Diavik Joint Venture [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Percentage of ownership interest exchanged in joint venture			60.00%
Contractual obligations corresponding to receivable or contingent asset			40.00%
Robe River Mining Co Pty Ltd [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			60.00%
Non-controlling interest (%), Subsidiary			40.00%
Robe River Mining Co Pty Ltd [member] | Robe river iron associates [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Non-controlling interest (%), Subsidiary			30.00%
North Mining Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			100.00%
North Mining Limited [member] | Robe river iron associates [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Non-controlling interest (%), Subsidiary			35.00%
Queensland Coal Pty Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			100.00%
Queensland Coal Pty Limited [member] | Hail Creek [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Percentage of ownership interest exchanged in joint venture			82.00%
Queensland Coal Pty Limited [member] | Kestrel Underground Coal Mine [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Percentage of ownership interest exchanged in joint venture			80.00%
Simfer Jersey Limited [member] | Ordinary shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			53.00%
Non-controlling interest (%), Subsidiary			47.00%
Simfer S.A. [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			85.00%
Non-controlling interest (%), Subsidiary			45.05%
Indirect interest in subsidiary			45.05%
QIT Madagascar Minerals SA [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			80.00%
Portion of additional economic interest held through non voting investment			5.00%
Portion of economic interest held through non voting investment			85.00%
Non-controlling interest voting rights			20.00%
QIT Madagascar Minerals SA [member] | Common shares [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			80.00%
Proportion of class held (%), Subsidiary			80.00%
QIT Madagascar Minerals SA [member] | Common Shares and Investment Certificates [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Non-controlling interest (%), Subsidiary			15.00%
Turquoise Hill Resources Ltd [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			50.79%
Turquoise Hill Resources Ltd [member] | Oyu Tolgoi LLC [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			66.00%
Rossing Uranium [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			68.60%
Proportion of class held (%), Subsidiary			35.57%
Non-controlling interest voting rights			64.43%
Richards Bay Mining (Proprietary) Limited [member] | B Ordinary, B Preference and Parent Preference Shares [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Ownership percentage in subsidiary			74.00%
Non-controlling interest (%), Subsidiary			26.00%

Principal subsidiaries - Summ_3

Principal subsidiaries - Summary of subsidiaries financial information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		$ 40,522	$ 40,030	$ 33,781
Profit after tax for the year		13,925	8,851	4,776
– attributable to non-controlling interests		287	89	159
– attributable to owners of Rio Tinto (net earnings)		13,638	8,762	4,617
Other comprehensive (loss)/income		(3,139)	3,088	(63)
Total comprehensive income for the year	[1]	10,786	11,939	4,713
– Non-current assets		70,047	76,554
– Current assets		20,168	18,678
– Non-current liabilities		(30,261)	(33,262)
Net assets/(liabilities)		49,823	51,115
Attributable to non-controlling interests		6,137	6,404
Equity attributable to owners of Rio Tinto (see Group balance sheet)		43,686	44,711	39,290	$ 44,542
Cash flow from operations		11,821	13,884	8,465
Dividends paid to holders of non-controlling interests in subsidiaries		(420)	(399)	$ (341)
Iron Ore Company of Canada [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		1,561	1,867
Profit after tax for the year		298	377
– attributable to non-controlling interests		122	156
– attributable to owners of Rio Tinto (net earnings)		176	221
Other comprehensive (loss)/income		(136)	144
Total comprehensive income for the year		162	521
– Non-current assets		2,376	2,535
– Current assets		459	714
– Current liabilities		(351)	(449)
– Non-current liabilities		(791)	(838)
Net assets/(liabilities)		1,693	1,962
Attributable to non-controlling interests		699	809
Equity attributable to owners of Rio Tinto (see Group balance sheet)		994	1,153
Cash flow from operations		553	840
Dividends paid to holders of non-controlling interests in subsidiaries		(178)	(162)
Energy Resources of Australia Limited [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		151	157
Profit after tax for the year		(241)	(29)
– attributable to non-controlling interests		1	(9)
– attributable to owners of Rio Tinto (net earnings)		(242)	(20)
Other comprehensive (loss)/income		2
Total comprehensive income for the year		(239)	(29)
– Non-current assets		74	57
– Current assets		311	406
– Current liabilities		(123)	(128)
– Non-current liabilities		(522)	(356)
Net assets/(liabilities)		(260)	(21)
Attributable to non-controlling interests		(6)	(7)
Equity attributable to owners of Rio Tinto (see Group balance sheet)		(254)	(14)
Cash flow from operations		(64)	(2)
Turquoise Hill [Member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		1,180	940
Profit after tax for the year		139	22
– attributable to non-controlling interests		14	(49)
– attributable to owners of Rio Tinto (net earnings)		125	71
Other comprehensive (loss)/income		(4)	4
Total comprehensive income for the year		135	26
– Non-current assets		10,375	9,008
– Current assets		3,813	4,953
– Current liabilities		(540)	(504)
– Non-current liabilities		(4,367)	(4,311)
Net assets/(liabilities)		9,281	9,146
Attributable to non-controlling interests		3,936	3,982
Equity attributable to owners of Rio Tinto (see Group balance sheet)		5,345	5,164
Cash flow from operations		357	295
Robe River Mining Co Pty Ltd [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		1,082	1,164
Profit after tax for the year		561	617
– attributable to non-controlling interests		218	242
– attributable to owners of Rio Tinto (net earnings)		343	375
Other comprehensive (loss)/income		(313)	238
Total comprehensive income for the year		248	855
– Non-current assets		2,610	2,927
– Current assets		710	875
– Current liabilities		(111)	(186)
– Non-current liabilities		(117)	(174)
Net assets/(liabilities)		3,092	3,442
Attributable to non-controlling interests		1,237	1,375
Equity attributable to owners of Rio Tinto (see Group balance sheet)		1,855	2,067
Cash flow from operations		933	1,048
Dividends paid to holders of non-controlling interests in subsidiaries		(224)	(230)
Other companies and eliminations [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		1,262	1,351
Profit after tax for the year		543	637
– attributable to owners of Rio Tinto (net earnings)		543	637
Other comprehensive (loss)/income		(203)	158
Total comprehensive income for the year		340	795
– Non-current assets		3,739	4,187
– Current assets		2,368	1,149
– Current liabilities		(235)	(1,357)
– Non-current liabilities		(3,977)	(2,244)
Net assets/(liabilities)		1,895	1,735
Equity attributable to owners of Rio Tinto (see Group balance sheet)		1,895	1,735
Cash flow from operations		1,151	1,207
Robe River [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Consolidated sales revenue		2,344	2,515
Profit after tax for the year		1,104	1,254
– attributable to non-controlling interests		218	242
– attributable to owners of Rio Tinto (net earnings)		886	1,012
Other comprehensive (loss)/income		(516)	396
Total comprehensive income for the year		588	1,650
– Non-current assets		6,349	7,114
– Current assets		3,078	2,024
– Current liabilities		(346)	(1,543)
– Non-current liabilities		(4,094)	(2,418)
Net assets/(liabilities)		4,987	5,177
Attributable to non-controlling interests		1,237	1,375
Equity attributable to owners of Rio Tinto (see Group balance sheet)		3,750	3,802
Cash flow from operations		2,084	2,255
Dividends paid to holders of non-controlling interests in subsidiaries		$ (224)	$ (230)
[1]	Refer to Group statement of comprehensive income for further details. Adjustments to other reserves include currency translation attributable to owners of Rio Tinto, other than that arising on Rio Tinto Limited’s share capital.

Principal subsidiaries - Summ_4

Principal subsidiaries - Summary of subsidiaries financial information (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Goodwill	$ 912	$ 1,037	$ 951
North Mining Limited [member] | Robe river iron associates [member]
Disclosure Of Significant Investments In Subsidiaries [Line Items]
Goodwill	$ 351	$ 389

Principal joint operations - Su

Principal joint operations - Summary of principle joint operations (Detail)	12 Months Ended
	Dec. 31, 2018
Tomago Aluminium Joint Venture [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Tomago Aluminium Joint Venture
Country of incorporation, Joint Operation	Australia
Principal activities, Joint Operation	Aluminium smelting
Group interest (%), Joint Operation	51.60%
Gladstone Power Station [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Gladstone Power Station
Country of incorporation, Joint Operation	Australia
Principal activities, Joint Operation	Power generation
Group interest (%), Joint Operation	42.10%
Hope Downs Joint Venture [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Hope Downs Joint Venture
Country of incorporation, Joint Operation	Australia
Principal activities, Joint Operation	Iron ore mining
Group interest (%), Joint Operation	50.00%
Queensland Alumina Limited [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Queensland Alumina Limited
Country of incorporation, Joint Operation	Australia
Principal activities, Joint Operation	Alumina production
Group interest (%), Joint Operation	80.00%
Pilbara Iron arrangement [Member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Pilbara Iron arrangement
Country of incorporation, Joint Operation	Australia
Principal activities, Joint Operation	Infrastructure, corporate and mining services
New Zealand Aluminium Smelters Limited [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	New Zealand Aluminium Smelters Limited
Country of incorporation, Joint Operation	New Zealand
Principal activities, Joint Operation	Aluminium smelting
Group interest (%), Joint Operation	79.36%
Aluminerie Alouette Inc. [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Aluminerie Alouette Inc.
Country of incorporation, Joint Operation	Canada
Principal activities, Joint Operation	Aluminium production
Group interest (%), Joint Operation	40.00%
Pechiney Reynolds Quebec Inc [member]
Disclosure Of Joint Operations [Line Items]
Company of operation, Joint Operation	Pechiney Reynolds Quebec Inc
Country of incorporation, Joint Operation	United States of America
Principal activities, Joint Operation	Aluminium smelting
Group interest (%), Joint Operation	50.20%

Principal joint operations - _2

Principal joint operations - Summary of principle joint operations (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018Subsidiary
New Zealand Aluminium Smelters Limited [member]
Disclosure Of Joint Operations [Line Items]
Group interest (%), Joint Operation	79.36%
Principal activities, Joint Operation	Aluminium smelting
Queensland Alumina Limited [member]
Disclosure Of Joint Operations [Line Items]
Group interest (%), Joint Operation	80.00%
Principal activities, Joint Operation	Alumina production
Pilbara Iron arrangement [Member]
Disclosure Of Joint Operations [Line Items]
Number of subsidiary	2
Company of operation, Subsidiary	Pilbara Iron (Company) Services Pty Ltd and Pilbara Iron Pty Ltd.
Principal activities, Joint Operation	Infrastructure, corporate and mining services
Pechiney Reynolds Quebec Inc [member]
Disclosure Of Joint Operations [Line Items]
Group interest (%), Joint Operation	50.20%
Principal activities, Joint Operation	Aluminium smelting
Pechiney Reynolds Quebec Inc [member] | Aluminerie De Becancour Inc [member]
Disclosure Of Joint Operations [Line Items]
Group interest (%), Joint Venture	50.10%
Company of operation	Aluminerie de Bécancour, Inc.
Principal activities, Joint Operation	Aluminium smelter
Country of incorporation, Joint Venture	Canada

Principal joint ventures - Summ

Principal joint ventures - Summary of joint ventures (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Joint Ventures [Line Items]
Rio Tinto Limited shares were held by Rio Tinto plc	0	0	0
Minera Escondida Limitada [member]
Disclosure Of Joint Ventures [Line Items]
Company of operation	Minera Escondida Limitada
Country of incorporation, Joint Venture	Chile
Principal activities, Joint Venture	Copper mining and refining
Group interest (%), Joint Venture	30.00%	30.00%
Sohar Aluminium Co. L.L.C. [member]
Disclosure Of Joint Ventures [Line Items]
Group interest (%), Joint Venture	20.00%	20.00%
Sohar Aluminium Co. L.L.C. [member] | Ordinary shares [Member]
Disclosure Of Joint Ventures [Line Items]
Company of operation	Sohar Aluminium Co. L.L.C.
Country of incorporation, Joint Venture	Oman
Principal activities, Joint Venture	Aluminium smelting; power generation
Rio Tinto Limited shares were held by Rio Tinto plc	37,500
Proportion of class held (%), Joint Venture	20.00%
Group interest (%), Joint Venture	20.00%

Principal joint ventures - Su_2

Principal joint ventures - Summary of joint ventures (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Minera Escondida Limitada [member]
Disclosure Of Joint Ventures [Line Items]
Group interest (%), Joint Venture	30.00%	30.00%
Minera Escondida Limitada [member] | BHP Billiton Member
Disclosure Of Joint Ventures [Line Items]
Ownership interest in joint venture held by joint partner	57.50%
Sohar Aluminium Co. L.L.C. [member]
Disclosure Of Joint Ventures [Line Items]
Group interest (%), Joint Venture	20.00%	20.00%

Principal joint ventures - Addi

Principal joint ventures - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Joint Ventures [Abstract]
Description of basis of preparation of summarized financial information of joint venture	Summarised financial information is shown on a 100 per cent basis. It represents the amounts shown in the joint ventures? financial statements prepared in accordance with IFRS under Group accounting policies, including fair value adjustments and amounts due to and from Rio Tinto.

Principal joint ventures - Su_3

Principal joint ventures - Summary financial information for joint ventures by fair value (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Joint Ventures [Line Items]
Consolidated sales revenue		$ 40,522	$ 40,030	$ 33,781
Depreciation and amortisation		(4,015)	(4,375)	(4,794)
Finance costs		(552)	(848)	(1,111)
Taxation		(4,242)	(3,965)	(1,567)
Profit after tax for the year		13,925	8,851	4,776
Total comprehensive income for the year	[1]	10,786	11,939	$ 4,713
– Non-current assets		70,047	76,554
– Current assets		20,168	18,678
– Non-current liabilities		(30,261)	(33,262)
Net assets		49,823	51,115
Cash and cash equivalents		10,773	10,550
Minera Escondida Limitada [member]
Disclosure Of Joint Ventures [Line Items]
Consolidated sales revenue		7,580	6,037
Depreciation and amortisation		(1,727)	(1,690)
Other operating costs		(3,230)	(2,617)
Operating profit		2,623	1,730
Finance costs		(163)	(120)
Taxation		(873)	(627)
Profit after tax for the year		1,587	983
Total comprehensive income for the year		1,587	983
– Non-current assets		13,027	13,814
– Current assets		2,413	2,760
– Current liabilities		(1,637)	(1,727)
– Non-current liabilities		(4,460)	(4,617)
Net assets		9,343	10,230
Cash and cash equivalents		697	460
– current financial liabilities		(230)	(330)
– non-current financial liabilities		(2,763)	(2,840)
Dividends received from joint venture (Rio Tinto share)		786	780
Sohar Aluminium Co. L.L.C. [member]
Disclosure Of Joint Ventures [Line Items]
Consolidated sales revenue		810	460
Depreciation and amortisation		(120)	(145)
Other operating costs		(440)	(205)
Operating profit		250	110
Finance costs		(35)	(35)
Taxation		(40)
Profit after tax for the year		175	75
Total comprehensive income for the year		175	75
– Non-current assets		3,085	3,230
– Current assets		340	305
– Current liabilities		(230)	(205)
– Non-current liabilities		(955)	(1,270)
Net assets		2,240	2,060
Cash and cash equivalents		15	95
– current financial liabilities		(100)	(130)
– non-current financial liabilities		$ (795)	$ (1,120)
[1]	Refer to Group statement of comprehensive income for further details. Adjustments to other reserves include currency translation attributable to owners of Rio Tinto, other than that arising on Rio Tinto Limited’s share capital.

Principal joint ventures - Reco

Principal joint ventures - Reconciliation of financial information for joint ventures by carrying value (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Joint Ventures [Line Items]
Net assets/(liabilities)	$ 49,823	$ 51,115
Minera Escondida Limitada [member]
Disclosure Of Joint Ventures [Line Items]
Group interest	30.00%	30.00%
Net assets/(liabilities)	$ 9,343	$ 10,230
Group's ownership interest	2,803	3,069
Other adjustments		4
Carrying value of Group's interest	$ 2,803	$ 3,073
Sohar Aluminium Co. L.L.C. [member]
Disclosure Of Joint Ventures [Line Items]
Group interest	20.00%	20.00%
Net assets/(liabilities)	$ 2,240	$ 2,060
Group's ownership interest	448	412
Other adjustments	(1)	(3)
Carrying value of Group's interest	$ 447	$ 409

Principal joint ventures - Re_2

Principal joint ventures - Reconciliation of financial information for joint ventures by carrying value (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Joint Ventures [Line Items]
– deferred tax liabilities	$ 3,673	$ 3,628
Investment in equity accounted units [member]
Disclosure Of Joint Ventures [Line Items]
– deferred tax liabilities	$ 413	$ 500

Principal associates - Summary

Principal associates - Summary of principal associates (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of associates [Line Items]
Rio Tinto Limited shares were held by Rio Tinto plc	0	0	0
Boyne Smelters Limited [member]
Disclosure of associates [Line Items]
Group interest (%), Associate	59.40%	59.40%
Boyne Smelters Limited [member] | Ordinary shares [Member]
Disclosure of associates [Line Items]
Company of operation, Associate	Boyne Smelters Limited
Country of incorporation, Associate	Australia
Principal activities, Associate	Aluminium smelting
Rio Tinto Limited shares were held by Rio Tinto plc	153,679,560
Proportion of class held (%), Associate	59.40%
Group interest (%), Associate	59.40%
Mineracao Rio do Norte S.A. [member]
Disclosure of associates [Line Items]
Group interest (%), Associate	12.00%
Mineracao Rio do Norte S.A. [member] | Ordinary shares [Member]
Disclosure of associates [Line Items]
Principal activities, Associate	Bauxite mining
Rio Tinto Limited shares were held by Rio Tinto plc	25,000,000,000
Proportion of class held (%), Associate	12.50%
Group interest (%), Associate	12.00%
Mineracao Rio do Norte S.A. [member] | Preferred Shares [member]
Disclosure of associates [Line Items]
Company of operation, Associate	Mineracao Rio do Norte S.A.
Principal activities, Associate	Bauxite mining
Rio Tinto Limited shares were held by Rio Tinto plc	47,000,000,000
Proportion of class held (%), Associate	11.75%
Halco (Mining) Inc [member] | Common shares [member]
Disclosure of associates [Line Items]
Company of operation, Associate	Halco (Mining) Inc
Country of incorporation, Associate	United States of America
Rio Tinto Limited shares were held by Rio Tinto plc	4,500
Proportion of class held (%), Associate	45.00%
Group interest (%), Associate	45.00%

Principal associates - Summar_2

Principal associates - Summary of principal associates (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018
Mineracao Rio do Norte S.A. [member]
Disclosure of associates [Line Items]
Group interest (%), Associate	12.00%
Halco (Mining) Inc [member] | Compagnie des Bauxites de Guine [member]
Disclosure of associates [Line Items]
Indirect interest in associate	51.00%
Company of operation, Subsidiary	Compagnie des Bauxites de Guinée
Country of incorporation, Subsidiary	Guinea

Principal associates - Addition

Principal associates - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Significant Investments In Associates [Abstract]
Description of basis of preparation of summarised financial information of associate	summarised financial information is shown on a 100% basis

Principal associates - Reconcil

Principal associates - Reconciliation of financial information for principal associates by carrying value (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of associates [Line Items]
Revenue		$ 40,522	$ 40,030	$ 33,781
(Loss)/profit after tax		13,925	8,851	4,776
Other comprehensive (loss)/income		(3,139)	3,088	(63)
Total comprehensive income for the year	[1]	10,786	11,939	$ 4,713
– Non-current assets		70,047	76,554
– Current assets		20,168	18,678
– Non-current liabilities		(30,261)	(33,262)
Net assets		49,823	51,115
Net assets/(liabilities)		49,823	51,115
Boyne Smelters Limited [member]
Disclosure of associates [Line Items]
(Loss)/profit after tax		(12)	5
Other comprehensive (loss)/income		(68)	56
Total comprehensive income for the year		(80)	61
– Non-current assets		1,268	1,468
– Current assets		93	88
– Current liabilities		(113)	(99)
– Non-current liabilities		(842)	(996)
Net assets		$ 406	$ 461
Group interest (%), Associate		59.40%	59.40%
Net assets/(liabilities)		$ 406	$ 461
Group's ownership interest		241	274
Quasi equity loans to equity accounted units		129	159
Carrying value of Group's interest		$ 370	$ 433
[1]	Refer to Group statement of comprehensive income for further details. Adjustments to other reserves include currency translation attributable to owners of Rio Tinto, other than that arising on Rio Tinto Limited’s share capital.

Principal associates - Summar_3

Principal associates - Summary information for joint ventures and associates that are not individually material to the group (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of associates [Line Items]
(Loss)/profit after tax		$ 13,925	$ 8,851	$ 4,776
Other comprehensive income		(3,139)	3,088	(63)
Total comprehensive income for the year	[1]	10,786	11,939	$ 4,713
Associates [Member]
Disclosure of associates [Line Items]
Carrying value of Group's interest		679	571
(Loss)/profit after tax		9	25
Other comprehensive income		(23)	14
Total comprehensive income for the year		$ (14)	$ 39
[1]	Refer to Group statement of comprehensive income for further details. Adjustments to other reserves include currency translation attributable to owners of Rio Tinto, other than that arising on Rio Tinto Limited’s share capital.

Purchases and sales of subsid_2

Purchases and sales of subsidiaries, joint ventures, associates and other interests in businesses - Additional information (Detail) - USD ($)

Dec. 21, 2018

Dec. 14, 2018

Aug. 01, 2018

Jun. 01, 2018

May 10, 2018

Sep. 01, 2017

Nov. 23, 2016

Jul. 20, 2016

Mar. 01, 2016

May 31, 2017

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Disclosure Of Acquisitions And Disposals [Line Items]

Purchased amount

$ 194,000,000

Current trade receivables

$ 2,167,000,000

$ 2,314,000,000

Profit before taxation

18,167,000,000

12,816,000,000

$ 6,343,000,000

Disposals of subsidiaries, joint ventures, unincorporated joint operations, and associates

7,733,000,000

2,675,000,000

761,000,000

2018 Disposals [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 1,700,000,000

2017 disposals [member] | Yancoal Australia Limited [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 2,690,000,000

Ownership interest in joint venture disposed

100.00%

Cash consideration for disposal

$ 2,450,000,000

2,540,000,000

Expected unconditional royalty payments to be received

$ 240,000,000

Unconditional guaranteed royalty payments received

$ 110,000,000

Unconditional guaranteed royalty received

90,000,000

Expected unconditional royalty payments

$ 40,000,000

2016 disposals [member] | New hope corporation limited [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 617,000,000

Ownership interest in joint venture disposed

40.00%

2016 disposals [member] | SIMEC [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 410,000,000

Cash received

$ 224,000,000

Simfer Jersey Limited [member] | Ordinary shares [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of purchased interest

53.00%

Non-controlling interest (%), Subsidiary

47.00%

Simfer S.A. [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of purchased interest

4.25%

Non-controlling interest (%), Subsidiary

45.05%

Simfer S.A. [member] | 2016 disposals [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of non-contributory shares

7.50%

Percentage of ordinary contributory shares upon second tranche

10.00%

Percentage of ordinary contributory shares

5.00%

Simfer S.A. [member] | Bottom of range [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of purchased interest

42.80%

Simfer S.A. [member] | Top of range [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of purchased interest

45.05%

Dunkerque Aluminium Smelter [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 500,000,000

Profit before taxation

$ 128,000,000

Proceeds from sale of a business

$ 385,000,000

Cash received from disposals

52,000,000

Grasberg [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 3,500,000,000

Gains on disposals of projects

2,146,000,000

Disposals of subsidiaries, joint ventures, unincorporated joint operations, and associates

$ 3,392,000,000

Grasberg [Member] | Copper and Gold Revenues [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Revenues, net of capital contribution.

$ 107,000,000

Carbone savoie [Member] | 2016 disposals [member] | Alandia industries [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Ownership interest in cash generating units disposed

100.00%

Bougainville Copper Limited [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Non-controlling interest (%), Subsidiary

36.40%

Bougainville Copper Limited [Member] | Equity Trustees Limited [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 0

Percentage of share holding transferred

53.83%

Bougainville Copper Limited [Member] | Autonomous Bougainville Government [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of ownership shares distributed

36.40%

Bougainville Copper Limited [Member] | Independent State of Papua New Guinea [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Percentage of ownership shares distributed

17.40%

Lochaber [member] | 2016 disposals [member] | SIMEC [member]

Disclosure Of Acquisitions And Disposals [Line Items]

Proportion of ownership interest disposed

100.00%

Elysis

Disclosure Of Acquisitions And Disposals [Line Items]

Cash investment in joint venture

$ 5,000,000

Fare value of patents

171,000,000

Fair value of intellectual property

$ 141,000,000

Whitehaven Coal Limited [Member] | 2018 Disposals [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 200,000,000

Ownership interest in joint venture disposed

75.00%

Cash received from disposals

$ 150,000,000

Gains on disposals of projects

195,000,000

Whitehaven Coal Limited [Member] | Due within 1 year [member] | 2018 Disposals [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Current trade receivables

$ 50,000,000

Hail Creek [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Profit before taxation

$ 1,141,000,000

Hail Creek [Member] | 2018 Disposals [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Ownership interest in joint venture disposed

82.00%

Net proceeds disposal of project

$ 1,545,000,000

Profit before taxation

$ 1,141,000,000

Valeria Project [Member] | 2018 Disposals [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Ownership interest in joint venture disposed

71.20%

Net proceeds disposal of project

$ 170,000,000

Valeria Project [Member] | 2018 Disposals [Member] | Land and Investments [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Net proceeds disposal of project

87,000,000

Profit before taxation

18,000,000

Valeria Project [Member] | 2018 Disposals [Member] | Undeveloped Properties [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Cash received from disposals

83,000,000

Profit before taxation

83,000,000

Kestrel Underground Coal Mine [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Profit before taxation

1,010,000,000

Kestrel Underground Coal Mine [Member] | 2018 Disposals [Member]

Disclosure Of Acquisitions And Disposals [Line Items]

Disposal amount

$ 2,250,000,000

Ownership interest in joint venture disposed

80.00%

Net proceeds disposal of project

$ 2,270,000,000

Profit before taxation

$ 1,010,000,000

Directors' and key management_3

Directors' and key management remuneration - Summary of aggregate remuneration calculated in accordance with UK companies act 2006 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Directors And Key Management Remuneration [Abstract]
Emoluments	$ 9,069	$ 8,339	$ 9,186
Long term incentive plans	2,923	4,685	3,071
Total	11,992	13,024	12,257
Pension contributions: defined contribution plans	80	$ 135	$ 69
Gains made on exercise of share options	$ 107

Directors' and key management_4

Directors' and key management remuneration - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)Director	Dec. 31, 2017USD ($)Director	Dec. 31, 2016USD ($)Director
Disclosure Of Directors And Key Management Remuneration [Line Items]
Aggregate remuneration incurred	$ 39,592,000	$ 31,543,000	$ 44,218,000
Aggregate pension contribution to defined contribution plans	629,000	415,000	3,461,000
Other employment costs	$ 2,360,000	$ 2,122,000	$ 2,295,000
Defined Benefit Plan
Disclosure Of Directors And Key Management Remuneration [Line Items]
Number of directors accrued retirement benefits under defined contribution arrangements | Director	0		1
Defined Contribution Plans
Disclosure Of Directors And Key Management Remuneration [Line Items]
Number of directors accrued retirement benefits under defined contribution arrangements | Director	3	2	2
Rio Tinto plc [member]
Disclosure Of Directors And Key Management Remuneration [Line Items]
Aggregate remuneration incurred	$ 11,465,000	$ 12,624,000	$ 10,630,000
Aggregate pension contribution to defined contribution plans	80,000	135,000	69,000
Rio Tinto Limited [member]
Disclosure Of Directors And Key Management Remuneration [Line Items]
Aggregate pension contribution to defined contribution plans	0	0	0
Aggregate remuneration including pension contributions and other retirement benefits	$ 607,000	$ 535,000	$ 1,696,000

Directors' and key management_5

Directors' and key management remuneration - Summary of aggregate compensation representing the expense recognised under IFRS (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Directors And Key Management Remuneration [Abstract]
Short-term employee benefits and costs	$ 23,978	$ 23,095	$ 22,269
Post-employment benefits	629	415	3,461
Employment termination benefits	69		2,682
Share-based payments	14,916	8,033	15,806
Total	$ 39,592	$ 31,543	$ 44,218

Auditors' remuneration - Audito

Auditors' remuneration - Auditors' remuneration (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Auditors Remuneration [Line Items]
Audit of the Group	$ 16.7	$ 14.3	$ 13.5
Audit-related assurance service	0.9	1	0.9
Other assurance services	3.3	2.3	0.6
Total assurance services	4.2	3.3	1.5
Tax compliance		0.3	0.5
Tax advisory services		0.2	0.1
Other non-audit services not covered above	0.2	0.7	1.8
Total non-audit services	4.4	4.5	3.9
Total Group Auditors’ remuneration	21.1	18.8	17.4
Audit of the financial statements of the Group’s subsidiaries	1.4	2	2.1
Fees in respect of pension scheme audits	0.1	0.5	0.3
Total audit fees payable to other accounting firms	1.5	2.5	2.4
Rio Tinto [member]
Auditors Remuneration [Line Items]
Audit of the Group	9.2	6.2	4.5
Subsidiaries [Member]
Auditors Remuneration [Line Items]
Audit of the Group	$ 7.5	$ 8.1	$ 9

Auditors' remuneration - Audi_2

Auditors' remuneration - Auditors' remuneration (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Auditors Remuneration [Line Items]
Tax advisory services		$ 200	$ 100
PWC [Member]
Auditors Remuneration [Line Items]
Auditors remuneration for audit services	$ 100
Auditors remuneration for non audit services	100
Tax advisory services	$ 40

Related-party transactions - Su

Related-party transactions - Summary of transactions and balances with equity accounted units (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of transactions between related parties [Line Items]
Dividends from equity accounted units	$ 800	$ 817	$ 253
Investments in equity accounted units	4,299	4,486
Loans to equity accounted units	38	39
Investment in equity accounted units [member]
Disclosure of transactions between related parties [Line Items]
Purchases from equity accounted units	(1,209)	(993)	(1,216)
Sales to equity accounted units	493	210	248
Dividends from equity accounted units	800	817	253
Net funding of equity accounted units	(9)	(3)	(12)
Investments in equity accounted units	4,299	4,486	5,019
Loans to equity accounted units	38	39	39
Loans from equity accounted units		(31)	(49)
Trade and other receivables: amounts due from equity accounted units (b)	278	299	298
Trade and other payables: amounts due to equity accounted units	$ (223)	$ (175)	$ (243)

Exchange rates in US$ - Summary

Exchange rates in US$ - Summary of principal exchange rate used in preparation of financial statements (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United Kingdom, Pounds
Disclosure Of Foreign Exchange Rates [Line Items]
Full-year average exchange rate per U.S.$	1.34	1.29	1.36
Year-end exchange rate per U.S.$	1.27	1.34	1.22
Australian dollar [Member]
Disclosure Of Foreign Exchange Rates [Line Items]
Full-year average exchange rate per U.S.$	0.75	0.77	0.74
Year-end exchange rate per U.S.$	0.70	0.78	0.72
Canadian dollar [Member]
Disclosure Of Foreign Exchange Rates [Line Items]
Full-year average exchange rate per U.S.$	0.77	0.77	0.76
Year-end exchange rate per U.S.$	0.73	0.79	0.74
Euro Member Countries, Euro
Disclosure Of Foreign Exchange Rates [Line Items]
Full-year average exchange rate per U.S.$	1.18	1.13	1.11
Year-end exchange rate per U.S.$	1.14	1.20	1.05
South African rand [Member]
Disclosure Of Foreign Exchange Rates [Line Items]
Full-year average exchange rate per U.S.$	0.076	0.075	0.068
Year-end exchange rate per U.S.$	0.069	0.081	0.073

Share-based payments - Charge h

Share-based payments - Charge has been recognised in income statement for Rio Tinto's share-based incentive plans, and the related liability (for cash-settled plans) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Liability at the end of the year	$ 16	$ 15
Charge recognised for the year	122	91	$ 116
Equity-settled plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Charge recognised for the year	118	88	$ 116
Cash-settled plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Liability at the end of the year	16	15
Charge recognised for the year	$ 4	$ 3

Share-based payments - Addition

Share-based payments - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)OptionInstrumentshares	Dec. 31, 2017USD ($)Optionshares
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Percentage of cancellations employees electing to withdraw their investment shares before vesting of their matching shares	15.00%
Options outstanding, number of options | Option	40,114	188,766
Aggregate Intrinsic Value Of Outstanding Share Options		$ 3,000,000
Liability for cash-settled awards	$ 16,000,000	$ 15,000,000
Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Percentage of share-based payment charge for plan	100.00%	100.00%
Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Percentage of share-based payment charge for plan	100.00%	100.00%
Share Option Plan [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Option expiry period	2,019
UK share plan [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of method of settlement for share-based payment arrangement	equity
Performance share plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of method of settlement for share-based payment arrangement	equity-settled
Information on how the fair value of share options granted was measured	Monte Carlo simulation model
Description of award granted for share-based payment arrangement	One-third of the awards granted from 2013 to 2017 (inclusive) are subject to an earnings margin performance target relative to ten global mining comparators.
Number of global mining comparators | Instrument	10
Percentage of forfeitures, prior to vesting, on outstanding awards	5.00%	5.00%
Share-based payments, fair value measurement description	As this is a non-market related performance condition, under IFRS 2, the fair value recognised is reviewed at each accounting date based on the directors’ expectations for the proportion vesting.
Vesting requirements for share based awards	Forfeitures prior to vesting are assumed at 5% per annum of outstanding awards (2017: 5% per annum).
Performance share plans [member] | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Cash-settled awards outstanding | shares	40,365
Liability for cash-settled awards	$ 11,000,000
Performance share plans [member] | Rio Tinto plc [member] | Top of range [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Cash-settled awards outstanding | shares		26,590
Liability for cash-settled awards		$ 9,000,000
Performance share plans [member] | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Cash-settled awards outstanding | shares	276,722	276,722
Management share plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of method of settlement for share-based payment arrangement	equity
Percentage of forfeitures, prior to vesting, on outstanding awards	7.00%	7.00%
Vesting requirements for share based awards	The vesting of these awards is dependent on service conditions being met.
Bonus deferral plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of method of settlement for share-based payment arrangement	equity
Percentage of forfeitures, prior to vesting, on outstanding awards	3.00%	3.00%
Vesting requirements for share based awards	The vesting of these awards is dependent only on service conditions being met.
Bonus deferral plans [member] | Executive directors and product group executives [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Vesting requirements for share based awards	50% of the bonuses
Bonus deferral plans [member] | Other executives [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of method of settlement for share-based payment arrangement	25% of the bonuses
Global employee share plans [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Description of method of settlement for share-based payment arrangement	equity
Percentage of forfeitures, prior to vesting, on outstanding awards	5.00%	5.00%
Vesting requirements for share based awards	The vesting of these matching awards is dependent on service conditions being met and the continued holding of investment shares by the participant until vesting.
Share Incentive Plans
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Liability for cash-settled awards	$ 5,000,000
Share Incentive Plans | Top of range [Member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Liability for cash-settled awards		$ 6,000,000
Share Incentive Plans | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Cash-settled awards outstanding | shares	46,543	33,443
Share Incentive Plans | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Cash-settled awards outstanding | shares	83,092	87,019

Share-based payments - Summary

Share-based payments - Summary of options outstanding and exercisable (Detail) $ in Millions	Dec. 31, 2018USD ($)Option	Dec. 31, 2018GBP (£)Option	Dec. 31, 2017Option
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Options outstanding, number	40,114	40,114	188,766
Aggregate intrinsic value | $	$ 1
Rio Tinto plc [member] | Exercise price GBPXX - GBPXX [member] | Share Option Plan [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Options outstanding, number	23,659	23,659
Weighted average exercise price per option | £		£ 17
Weighted average remaining contractual life Years	0.22	0.22
Aggregate intrinsic value | $	$ 1
Rio Tinto Limited [member] | Exercise price A$XX [member] | Share Option Plan [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Options outstanding, number	16,455	16,455
Weighted average exercise price per option | £		£ 33
Weighted average remaining contractual life Years	0.21	0.21

Share-based payments - Summar_2

Share-based payments - Summary of options outstanding and exercisable (Parenthetical) (Detail) - Dec. 31, 2018 - Share Option Plan [member] $ in Millions	AUD ($)	GBP (£)
Rio Tinto plc [member] | Bottom of range [Member] | Ranges Of Exercise Prices For Outstanding Share Options Three
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Options outstanding, exercise price		£ 16
Rio Tinto plc [member] | Top of range [Member] | Ranges Of Exercise Prices For Outstanding Share Options Three
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Options outstanding, exercise price		£ 25
Rio Tinto Limited [member] | Ranges Of Exercise Prices For Outstanding Share Options Four
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Options outstanding, exercise price | $	$ 33

Share-based payments -Summary o

Share-based payments -Summary of performance share plans (Detail)	12 Months Ended
	Dec. 31, 2018AUD ($)shares	Dec. 31, 2018GBP (£)shares	Dec. 31, 2017AUD ($)shares	Dec. 31, 2017GBP (£)shares
Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of transfers from equity to cash settled			(276,722)	(276,722)
Performance share plans [member] | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Weighted average fair value at grant date, non-vested shares at beginning balance | £		£ 20.47		£ 18.27
Weighted average fair value at grant date, non-vested shares, awarded | £		26.87		24.64
Weighted average fair value at grant date, non-vested shares, forfeited | £		21.45		16.28
Weighted average fair value at grant date, non-vested shares, failed performance conditions | £		14.54		16.25
Weighted average fair value at grant date, non-vested shares, vested | £		21.57		21.51
Weighted average fair value at grant date, non-vested shares at ending balance | £		£ 21.86		£ 20.47
Number of non-vested shares at beginning balance	3,555,274	3,555,274	2,883,053	2,883,053
Number of non-vested shares, awarded	801,047	801,047	1,198,677	1,198,677
Number of non-vested shares, forfeited	(188,761)	(188,761)	(199,435)	(199,435)
Number of non-vested shares, failed performance conditions	(107,625)	(107,625)	(161,966)	(161,966)
Number of non-vested shares, vested	(214,853)	(214,853)	(165,055)	(165,055)
Number of non-vested shares at ending balance	3,845,082	3,845,082	3,555,274	3,555,274
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | £		£ 42.57		£ 31.04
Weighted average share price, Vested awards settled in cash during the year (including dividend shares applied on vesting) | £		£ 42.40
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	248,965	248,965	188,383	188,383
Number of vested awards settled in cash during the year (including dividend shares applied on vesting)	991	991
Performance share plans [member] | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Weighted average fair value at grant date, non-vested shares at beginning balance | $	$ 40.13		$ 37.52
Weighted average fair value at grant date, non-vested shares, awarded | $	53.85		45.84
Weighted average fair value at grant date, non-vested shares, forfeited | $	43.83		36.59
Weighted average fair value at grant date, non-vested shares, failed performance conditions | $	27.67		30.89
Weighted average fair value at grant date, non-vested shares, vested | $	40.85		40.79
Weighted average fair value transfers from equity to cash settled | $			40.11
Weighted average fair value at grant date, non-vested shares at ending balance | $	$ 43.34		$ 40.13
Number of non-vested shares at beginning balance	1,609,154	1,609,154	1,590,957	1,590,957
Number of non-vested shares, awarded	387,298	387,298	529,776	529,776
Number of non-vested shares, forfeited	(36,530)	(36,530)	(36,716)	(36,716)
Number of non-vested shares, failed performance conditions	(54,322)	(54,322)	(113,857)	(113,857)
Number of non-vested shares, vested	(108,321)	(108,321)	(84,284)	(84,284)
Number of non-vested shares at ending balance	1,797,279	1,797,279	1,609,154	1,609,154
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $	$ 82.97		$ 63.09
Weighted average share price, Vested awards settled in cash during the year (including dividend shares applied on vesting) | $	$ 82.08		$ 62.81
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	105,374	105,374	73,311	73,311
Number of vested awards settled in cash during the year (including dividend shares applied on vesting)	9,959	9,959	5,010	5,010

Share-based payments -Managemen

Share-based payments -Management Share Plans, Bonus Deferral Plans, Global Employee Share Plans and UK Share Plan (combined) (Detail)	12 Months Ended
	Dec. 31, 2018AUD ($)	Dec. 31, 2018GBP (£)	Dec. 31, 2017AUD ($)	Dec. 31, 2017GBP (£)	Dec. 31, 2018GBP (£)	Dec. 31, 2017GBP (£)	Dec. 31, 2016AUD ($)	Dec. 31, 2016GBP (£)
Share Incentive Plans | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	3,042,020		3,473,092		3,042,020	3,473,092	3,305,966	3,305,966
Number of non-vested shares, awarded	1,135,103	1,135,103	1,499,374	1,499,374
Number of non-vested shares, forfeited	250,853	250,853	159,669	159,669
Number of non-vested shares, Cancelled	(33,563)	(33,563)	(51,773)	(51,773)
Number of non-vested shares, vested	1,281,759	1,281,759	1,120,806	1,120,806
Weighted average fair value at grant date, non-vested shares at beginning balance					£ 31.43	£ 27.23		£ 26
Weighted average fair value at grant date, non-vested shares, awarded		£ 39.49		£ 32.50
Weighted average fair value at grant date, non-vested shares, forfeited		30.26		29.46
Weighted average fair value at grant date, non-vested shares, cancelled		26.52		25.82
Weighted average fair value at grant date, non-vested shares, vested		£ 27.54		£ 30.41
Share Incentive Plans | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	2,613,930		2,933,237		2,613,930	2,933,237	2,986,080	2,986,080
Number of non-vested shares, awarded	943,315	943,315	1,156,078	1,156,078
Number of non-vested shares, forfeited	185,062	185,062	127,905	127,905
Number of non-vested shares, Cancelled	(36,613)	(36,613)	(95,203)	(95,203)
Number of non-vested shares, vested	1,040,947	1,040,947	985,813	985,813
Weighted average fair value at grant date, non-vested shares at beginning balance | $	$ 61.71		$ 54.15				$ 53.32
Weighted average fair value at grant date, non-vested shares, awarded | $	78.36		61.05
Weighted average fair value at grant date, non-vested shares, forfeited | $	64.60		53.61
Weighted average fair value at grant date, non-vested shares, cancelled | $	52.84		51.18
Weighted average fair value at grant date, non-vested shares, vested | $	$ 55.30		$ 60.06
Management share plans [member] | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	1,666,082		1,897,318		1,666,082	1,897,318
Weighted average fair value at grant date, non-vested shares at beginning balance					£ 32.52	£ 27.99
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	669,678	669,678	653,776	653,776
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)		£ 40.03		£ 35.33
Management share plans [member] | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	1,520,292		1,617,838		1,520,292	1,617,838
Weighted average fair value at grant date, non-vested shares at beginning balance | $	$ 64.06		$ 55.42
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	570,173	570,173	577,083	577,083
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $	$ 80.87		$ 67.93
Bonus deferral plans [member] | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	203,900		281,994		203,900	281,994
Weighted average fair value at grant date, non-vested shares at beginning balance					£ 37.86	£ 25.53
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	221,198	221,198	170,036	170,036
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)		£ 37.69		£ 34.44
Bonus deferral plans [member] | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	127,423		153,966		127,423	153,966
Weighted average fair value at grant date, non-vested shares at beginning balance | $	$ 71.93		$ 52.83
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	108,001	108,001	88,644	88,644
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $	$ 75.36		$ 69.98
Global employee share plans [member] | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	1,102,322		1,196,937		1,102,322	1,196,937
Weighted average fair value at grant date, non-vested shares at beginning balance					£ 28.68	£ 26.42
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	451,710	451,710	382,585	382,585
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)		£ 39.06		£ 33.56
Global employee share plans [member] | Rio Tinto Limited [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	966,215		1,161,433		966,215	1,161,433
Weighted average fair value at grant date, non-vested shares at beginning balance | $	$ 56.66		$ 52.54
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	473,420	473,420	466,308	466,308
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $	$ 78.78		$ 65.10
UK share plan [member] | Rio Tinto plc [member]
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]
Number of non-vested shares at beginning balance	69,716		96,843		69,716	96,843
Weighted average fair value at grant date, non-vested shares at beginning balance					£ 29.90	£ 27.14
Number of vested awards settled in shares during the year (including dividend shares applied on vesting)	16,968	16,968	11,120	11,120
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)		£ 38.21		£ 34.56

Post-retirement benefits - Summ

Post-retirement benefits - Summary of fair value of plan assets (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	100.00%	100.00%
Equities [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	20.70%	32.40%
Quoted [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	16.70%	28.60%
Private [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	4.00%	3.80%
Bonds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	63.60%	53.20%
Government fixed income bonds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	18.00%	14.30%
Government inflation- linked bonds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	15.50%	13.10%
Corporate and other publicly quoted bonds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	27.10%	23.50%
Private bonds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	3.00%	2.30%
Property [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	11.00%	11.20%
Quoted property funds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	5.10%	5.80%
Unquoted property funds [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	5.90%	5.40%
Qualifying Insurance policies [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	0.10%	0.20%
Cash & other [member]
Disclosure of fair value of plan assets [Line Items]
Proportions of total fair value of assets	4.60%	3.00%

Post-retirement benefits - Addi

Post-retirement benefits - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of defined benefit plans [Line Items]
Securities included in fair value of plan assets	$ 3	$ 13
Defined benefit expenses excluded form unerlying earnings	0	$ 0	$ 0
Estimated contributions to defined benefit pension plans for 2019	$ 260
Percentage of costs, contributions, gains and losses	100.00%
Defined benefit obligation weighted average expected future life time	27 years	27 years
Defined benefit obligation weighted average expected future life time at man aged 60 in 2036	28 years	28 years
Healthcare plans [member]
Disclosure of defined benefit plans [Line Items]
Discount rate	4.20%	3.60%
Medical trend rate	7.60%	9.80%
Reduction in medical trend rate	4.60%	4.70%
UK Schemes [Member]
Disclosure of defined benefit plans [Line Items]
Past service cost, to the current estimate cost of benefits	$ 9
Discount rate	2.80%	2.30%

Post-retirement benefits - Su_2

Post-retirement benefits - Summary of maturity of defined benefit obligations (Detail) - yr	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of defined benefit plans [Line Items]
Proportion relating to current employees	19.00%	20.00%	21.00%
Proportion relating to former employees not yet retired	11.00%	11.00%	12.00%
Proportion relating to retirees	70.00%	69.00%	67.00%
Defined benefit obligation	100.00%	100.00%	100.00%
Average duration of obligations (years)	13.4	13.9	14.3
Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Proportion relating to current employees	20.00%
Proportion relating to former employees not yet retired	11.00%
Proportion relating to retirees	69.00%
Defined benefit obligation	100.00%
Average duration of obligations (years)	13.4
Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Proportion relating to current employees	15.00%
Proportion relating to former employees not yet retired	2.00%
Proportion relating to retirees	83.00%
Defined benefit obligation	100.00%
Average duration of obligations (years)	12.7

Post-retirement benefits - Su_3

Post-retirement benefits - Summary of geographical distribution of defined benefit obligations (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	100.00%	100.00%	100.00%
Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	100.00%
Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	100.00%
Canada [Member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	48.00%	49.00%	46.00%
Canada [Member] | Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	49.00%
Canada [Member] | Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	39.00%
United Kingdom [Member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	28.00%	27.00%	27.00%
United Kingdom [Member] | Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	30.00%
United Kingdom [Member] | Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	2.00%
United States [Member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	14.00%	14.00%	16.00%
United States [Member] | Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	11.00%
United States [Member] | Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	56.00%
Switzerland [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	5.00%	5.00%	5.00%
Switzerland [member] | Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	5.00%
Switzerland [member] | Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	0.00%
Other countries [Member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	5.00%	5.00%	6.00%
Other countries [Member] | Pension benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	5.00%
Other countries [Member] | Other Benefits [member]
Disclosure of defined benefit plans [Line Items]
Defined benefit obligation	3.00%

Post-retirement benefits - Su_4

Post-retirement benefits - Summary of total expense recognised in the income statement (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]
Current employer service cost for defined benefit plans	$ (165)	$ (155)	$ (158)
Past service (cost)/income	(36)	4
Curtailment gains	2	1	5
Settlement gains	5	1
Net interest on net defined benefit liability	(79)	(79)	(90)
Non-investment expenses paid from the plans	(15)	(17)	(22)
Total defined benefit expense	(288)	(245)	(265)
Current employer service cost for defined contribution and industry-wide plans	(244)	(255)	(257)
Total expense recognised in the income statement	(532)	$ (500)	$ (522)
Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Current employer service cost for defined benefit plans	(156)
Past service (cost)/income	(34)
Curtailment gains	2
Settlement gains	5
Net interest on net defined benefit liability	(44)
Non-investment expenses paid from the plans	(15)
Total defined benefit expense	(242)
Current employer service cost for defined contribution and industry-wide plans	(242)
Total expense recognised in the income statement	(484)
Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Current employer service cost for defined benefit plans	(9)
Past service (cost)/income	(2)
Net interest on net defined benefit liability	(35)
Total defined benefit expense	(46)
Current employer service cost for defined contribution and industry-wide plans	(2)
Total expense recognised in the income statement	$ (48)

Post-retirement benefits - Su_5

Post-retirement benefits - Summary of total amount recognised in other comprehensive income before tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Abstract]
Actuarial gains/(losses)	$ 1,382	$ (855)	$ (1,120)
Return on assets (net of interest on assets)	(527)	894	1,031
Gain/(loss) on application of asset ceiling	52	(33)	(1)
Total gain/(loss) recognised in other comprehensive income	$ 907	$ 6	$ (90)

Post-retirement benefits - Su_6

Post-retirement benefits - Summary of amount recognised in balance sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	$ (1,551)	$ (2,499)	$ (2,542)
Effect of asset ceiling		(111)
Deficits	(2,486)	(3,370)
Surpluses	935	871
Net deficits on pension plans	(680)	(1,501)
Unfunded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Unfunded post-retirement healthcare obligation	(871)	(998)
Pension benefits [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(680)	(1,501)
Deficits	(1,615)
Surpluses	935
Net deficits on pension plans	(680)
Other Benefits [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(871)	(998)
Deficits	(871)
Other Benefits [member] | Unfunded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Unfunded post-retirement healthcare obligation	(871)
Plan assets [Member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	13,203	15,257	13,749
Plan assets [Member] | Pension benefits [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	13,203	15,257
Present value of defined benefit obligation [Member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(14,754)	(17,645)	$ (16,228)
Present value of defined benefit obligation [Member] | Funded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(13,482)	(16,199)
Present value of defined benefit obligation [Member] | Unfunded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(1,272)	(1,446)
Present value of defined benefit obligation [Member] | Pension benefits [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(13,883)	(16,647)
Present value of defined benefit obligation [Member] | Pension benefits [member] | Funded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(13,482)
Present value of defined benefit obligation [Member] | Pension benefits [member] | Unfunded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(401)
Present value of defined benefit obligation [Member] | Other Benefits [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	(871)	$ (998)
Present value of defined benefit obligation [Member] | Other Benefits [member] | Unfunded [member]
Disclosure of information about amounts recognized in balance sheet [Line Items]
Net deficit to be shown in the balance sheet	$ (871)

Post-retirement benefits - Su_7

Post-retirement benefits - Summary of funding policy and contributions to plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]
Contributions to defined benefit plans	$ 248	$ 404	$ 464
Contributions to defined contribution plans	244	243	240
Contributions to industry-wide plans		12	17
Total	492	$ 659	$ 721
Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Contributions to defined benefit plans	204
Contributions to defined contribution plans	242
Total	446
Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Contributions to defined benefit plans	44
Contributions to defined contribution plans	2
Total	$ 46

Post-retirement benefits - Su_8

Post-retirement benefits - Summary of movement in net defined benefit liability (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	$ (2,499)	$ (2,542)
Amounts recognised in Income statement	(288)	(245)	$ (265)
Amounts recognised in Other comprehensive income	907	6	(90)
Contributions by employer	248	404	464
Arrangements divested	(10)	13
Currency exchange rate (loss)/gain	91	(135)
Ending balance	(1,551)	(2,499)	$ (2,542)
Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(1,501)
Amounts recognised in Income statement	(242)
Amounts recognised in Other comprehensive income	812
Contributions by employer	204
Arrangements divested	(10)
Currency exchange rate (loss)/gain	57
Ending balance	(680)	(1,501)
Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(998)
Amounts recognised in Income statement	(46)
Amounts recognised in Other comprehensive income	95
Contributions by employer	44
Currency exchange rate (loss)/gain	34
Ending balance	$ (871)	$ (998)

Post-retirement benefits - Su_9

Post-retirement benefits - Summary of movement in present value of obligation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	$ (2,499)	$ (2,542)
Current employer service costs	165	155	$ 158
Curtailment gains	2	1	5
Settlements	(5)	(1)
Interest	(79)	(79)	(90)
Actuarial losses to equity accounted units	(1,382)	855	1,120
Arrangements divested	(10)	13
Currency exchange rate (loss)/gain	91	(135)
Ending balance	(1,551)	(2,499)	(2,542)
Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(1,501)
Current employer service costs	156
Curtailment gains	2
Settlements	(5)
Interest	(44)
Arrangements divested	(10)
Currency exchange rate (loss)/gain	57
Ending balance	(680)	(1,501)
Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(998)
Current employer service costs	9
Interest	(35)
Currency exchange rate (loss)/gain	34
Ending balance	(871)	(998)
Present value of defined benefit obligation [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(17,645)	(16,228)
Current employer service costs	(165)	(155)
Past service (cost)/income	(36)	4
Curtailment gains	2	1
Settlements	299	307
Interest	(503)	(532)
Contributions by plan participants	(24)	(23)
Benefits paid	915	949
Experience gains	32	7
Actuarial losses to equity accounted units	1,349	(718)
Changes in demographic assumptions gain/(loss)	1	(144)
Arrangements divested	94	13
Currency exchange rate (loss)/gain	927	(1,126)
Ending balance	(14,754)	(17,645)	$ (16,228)
Present value of defined benefit obligation [Member] | Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(16,647)
Current employer service costs	(156)
Past service (cost)/income	(34)
Curtailment gains	2
Settlements	299
Interest	(468)
Contributions by plan participants	(24)
Benefits paid	871
Experience gains	11
Actuarial losses to equity accounted units	1,276
Arrangements divested	94
Currency exchange rate (loss)/gain	893
Ending balance	(13,883)	(16,647)
Present value of defined benefit obligation [Member] | Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(998)
Current employer service costs	(9)
Past service (cost)/income	(2)
Interest	(35)
Benefits paid	44
Experience gains	21
Actuarial losses to equity accounted units	73
Changes in demographic assumptions gain/(loss)	1
Currency exchange rate (loss)/gain	34
Ending balance	$ (871)	$ (998)

Post-retirement benefits - S_10

Post-retirement benefits - Summary of movement in plan assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	$ (2,499)	$ (2,542)
Settlements	(5)	(1)
Interest	(79)	(79)	$ (90)
Contributions by employer	248	404	464
Non-investment expenses	(15)	(17)	(22)
Return on plan assets (net of interest on assets)	527	(894)	(1,031)
Arrangements divested	(10)	13
Currency exchange rate (loss)/gain	91	(135)
Ending balance	(1,551)	(2,499)	(2,542)
Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(1,501)
Settlements	(5)
Interest	(44)
Contributions by employer	204
Non-investment expenses	(15)
Arrangements divested	(10)
Currency exchange rate (loss)/gain	57
Ending balance	(680)	(1,501)
Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(998)
Interest	(35)
Contributions by employer	44
Currency exchange rate (loss)/gain	34
Ending balance	(871)	(998)
Plan assets [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	15,257	13,749
Settlements	(294)	(306)
Interest	434	459
Contributions by plan participants	24	23
Contributions by employer	248	404
Benefits paid	(915)	(949)
Non-investment expenses	(15)	(17)
Return on plan assets (net of interest on assets)	(527)	894
Arrangements divested	(161)
Currency exchange rate (loss)/gain	(848)	1,000
Ending balance	13,203	15,257	$ 13,749
Plan assets [Member] | Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	15,257
Settlements	(294)
Interest	434
Contributions by plan participants	24
Contributions by employer	204
Benefits paid	(871)
Non-investment expenses	(15)
Return on plan assets (net of interest on assets)	(527)
Arrangements divested	(161)
Currency exchange rate (loss)/gain	(848)
Ending balance	13,203	$ 15,257
Plan assets [Member] | Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Contributions by employer	44
Benefits paid	$ (44)

Post-retirement benefits - S_11

Post-retirement benefits - Summary of movement in effect of the asset ceiling (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	$ (2,499)	$ (2,542)
Interest	(79)	(79)	$ (90)
Movement in the effect of the asset ceiling	52	(33)	(1)
Currency exchange rate (loss)/gain	91	(135)
Ending balance	(1,551)	(2,499)	(2,542)
Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(1,501)
Interest	(44)
Currency exchange rate (loss)/gain	57
Ending balance	(680)	(1,501)
Other Benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(998)
Interest	(35)
Currency exchange rate (loss)/gain	34
Ending balance	(871)	(998)
Effect of asset ceiling [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(111)	(63)
Interest	(10)	(6)
Movement in the effect of the asset ceiling	52	(33)
Arrangements divested and other transfers	57
Currency exchange rate (loss)/gain	12	(9)
Ending balance		(111)	$ (63)
Effect of asset ceiling [member] | Pension benefits [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	(111)
Interest	(10)
Movement in the effect of the asset ceiling	52
Arrangements divested and other transfers	57
Currency exchange rate (loss)/gain	$ 12
Ending balance		$ (111)

Post-retirement benefits - S_12

Post-retirement benefits - Summary of main assumptions rate for valuations of plans (Detail)	Dec. 31, 2018	Dec. 31, 2017
Canada [Member]
Disclosure of defined benefit plans [Line Items]
Discount rate	3.90%	3.40%
Inflation	1.60%	1.80%
Rate of increase in pensions	0.20%	0.50%
Rate of increase in salaries	2.90%	3.10%
United Kingdom [Member]
Disclosure of defined benefit plans [Line Items]
Discount rate	2.80%	2.30%
Inflation	3.30%	3.20%
Rate of increase in pensions	2.90%	2.80%
Rate of increase in salaries	3.70%	3.60%
United States [Member]
Disclosure of defined benefit plans [Line Items]
Discount rate	4.20%	3.50%
Inflation	2.00%	2.10%
Rate of increase in pensions	0.00%	0.00%
Rate of increase in salaries	3.50%	3.60%
Switzerland [member]
Disclosure of defined benefit plans [Line Items]
Discount rate	0.70%	0.50%
Inflation	1.20%	1.20%
Rate of increase in pensions	0.00%	0.40%
Rate of increase in salaries	2.20%	2.20%

Post-retirement benefits - S_13

Post-retirement benefits - Summary of main assumptions rate for valuations of plans (Parenthetical) (Detail)	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Net Defined Benefit Liability Asset [Abstract]
Assumption for the consumer price index	2.20%	2.10%

Post-retirement benefits - Resu

Post-retirement benefits - Results summary of sensitivity analysis (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Actuarial assumption of discount rates [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	$ 782	$ 1,091
Decrease of actuarial assumption	(832)	(1,169)
Actuarial assumption of discount rates [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	51	59
Decrease of actuarial assumption	(55)	(63)
Actuarial assumption of expected rates of inflation [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	(389)	(579)
Decrease of actuarial assumption	369	550
Actuarial assumption of expected rates of inflation [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	(17)	(20)
Decrease of actuarial assumption	15	18
Actuarial assumption of expected rates of salary increases [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	(46)	(74)
Decrease of actuarial assumption	45	72
Actuarial assumption of expected rates of salary increases [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	(1)	(1)
Decrease of actuarial assumption	1	1
Actuarial assumption of allowance for future improvements in longevity [member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	381	509
Decrease of actuarial assumption	(381)	(509)
Actuarial assumption of allowance for future improvements in longevity [member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of actuarial assumption	18	20
Decrease of actuarial assumption	$ (18)	$ (20)

Post-retirement benefits - Re_2

Post-retirement benefits - Results summary of sensitivity analysis (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Actuarial assumption of discount rates [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of discount rates [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of inflation [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of inflation [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of salary increases [Member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of expected rates of salary increases [Member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase of percentage points	0.50%	0.50%
Decrease of percentage points	0.50%	0.50%
Actuarial assumption of allowance for future improvements in longevity [member] | Pensions [member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase in actuarial assumption of longevity trend	1 year	1 year
Decrease in actuarial assumption of longevity trend	1 year	1 year
Actuarial assumption of allowance for future improvements in longevity [member] | Other retirement benefits [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase in actuarial assumption of longevity trend	1 year	1 year
Decrease in actuarial assumption of longevity trend	1 year	1 year

New Standards and Interpretat_3

New Standards and Interpretations Adopted in the Current Year - Schedule of impact on equity attributable to owners of Rio Tinto due to adoption of IFRS 9 and IFRS 15 (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of initial application of standards or interpretations [Line Items]
Equity attributable to owners of Rio Tinto (see Group balance sheet)	$ 43,686	$ 44,542	$ 44,711	$ 39,290
Previously Stated [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Equity attributable to owners of Rio Tinto (see Group balance sheet)		44,711
Increase (decrease) due to changes in accounting policy required by IFRSs [Member] | IFRS 9 [member]
Disclosure of initial application of standards or interpretations [Line Items]
IFRS 9 Impairment provision resulting from application of the Expected Credit Loss (ECL) model and revaluations		(5)
Increase (decrease) due to changes in accounting policy required by IFRSs [Member] | IFRS 15 [member]
Disclosure of initial application of standards or interpretations [Line Items]
IFRS 15 De-recognition of receivable arising from uplift transaction		$ (164)

New Standards and Interpretat_4

New Standards and Interpretations Adopted in the Current Year - Summary of impact of transition to IFRS 9 on retained earnings (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]
Retained earnings	$ 27,025		$ 23,761
Revaluation of funds		$ 1
IFRS 9 [member]
Disclosure Of Financial Instruments [Line Items]
Retained earnings			$ 23,761
Costs of hedging adjustment		22
Reclassification of equity investments from available-for-sale to FVPL		12
Impairment provision resulting from the application of the ECL model		(7)
Tax impact		1
Revaluation of funds		1
Adjustment to retained earnings from adoption of IFRS 9 on 1 January 2018 (sub-total)		(15)
Retained Earnings 1 January 2018 IFRS 9 (Before Restatement for IFRS 15) [Member] | IFRS 9 [member]
Disclosure Of Financial Instruments [Line Items]
Retained earnings		$ 23,746

New Standards and Interpretat_5

New Standards and Interpretations Adopted in the Current Year - Summary of financial assets classified into appropriate IFRS 9 categories (Detail) $ in Millions	Jan. 01, 2018USD ($)
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	$ 1,300
Revaluation of funds	1
Opening balance – IFRS 9 (including expected credit losses and revaluation of funds)	15,282
IAS 39 [member]
Disclosure Of Financial Instruments [Line Items]
Financial Assets	15,288
IFRS 9 [member]
Disclosure Of Financial Instruments [Line Items]
Financial Assets	15,288
Impairment provision resulting from the application of the ECL model	(7)
IFRS 9 [member] | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Financial Assets	10,707
IFRS 9 [member] | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Financial Assets	46
IFRS 9 [member] | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Financial Assets	4,535
IAS 39 Classification Loans Receivable Held To Maturity | IAS 39 [member]
Disclosure Of Financial Instruments [Line Items]
Financial Assets	1,482
IAS 39 Classification Loans Receivable Held To Maturity | Other Investment Including Loans | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassification of a financial asset from held to maturity to FVPL	6
IAS 39 Classification Loans Receivable Held To Maturity | Cash and cash equivalents [member] | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	7,813
IAS 39 Classification Loans Receivable Held To Maturity | Trade And Other Receivable | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	1,316
IAS 39 Classification Loans Receivable Held To Maturity | Investments In Equity Shares And Funds | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	90
IAS 39 Classification Loans Receivable Held To Maturity | IAS 39 [member]
Disclosure Of Financial Instruments [Line Items]
Financial Assets	136
IAS 39 Classification Loans Receivable Held To Maturity | Investments In Equity Shares And Funds | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	(90)
IAS 39 Classification Loans Receivable Held To Maturity | IAS 39 [member]
Disclosure Of Financial Instruments [Line Items]
Financial Assets	13,670
IAS 39 Classification Loans Receivable Held To Maturity | Other Investment Including Loans | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassification of a financial asset from held to maturity to FVPL	(6)
IAS 39 Classification Loans Receivable Held To Maturity | Cash and cash equivalents [member] | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	(7,813)
IAS 39 Classification Loans Receivable Held To Maturity | Trade And Other Receivable | IFRS 9 Classification Amortised Cost
Disclosure Of Financial Instruments [Line Items]
Reclassifcation of money market funds from amortised cost to FVPL	$ (1,316)

New Standards and Interpretat_6

New Standards and Interpretations Adopted in the Current Year - Summary of financial assets classified into appropriate IFRS 9 categories (Parenthetical) (Detail) $ in Billions	Jan. 01, 2018USD ($)
Disclosure Of Initial Application Of Standards Or Interpretations [Abstract]
Money market funds	$ 7.8
Reclassification of trade and other receivables from amortised cost to FVPL	$ 1.3

New Standards and Interpretat_7

New Standards and Interpretations Adopted in the Current Year - Summary of retained earnings and reserves (Detail)Disclosure - Other disclosures - Summary of retained earnings and reserves (Detail) $ in Millions	Jan. 01, 2018USD ($)
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance	$ 12,284
Available for sale revaluation reserves [member] | IFRS 9 [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance	20
Reclassification of equity investments from AfS	(20)
Total impact	(20)
Effect On FVOCI Reserve [Member] | IFRS 9 [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Reclassification of equity investments from AfS	8
Total impact	8
Ending balance	8
Cost of Hedging Reserve [Member] | IFRS 9 [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Impact of costs of hedging adjustment	26
Total impact	26
Ending balance	26
Cash Flow Hedge Reserve [Member] | IFRS 9 [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance	32
Impact of costs of hedging adjustment	(4)
Total impact	(4)
Ending balance	28
Effect on Retained Earnings [Member] | IFRS 9 [member]
Disclosure Of Other Reserves And Retained Earnings [Line Items]
Beginning balance	23,761
Reclassification of equity investments from AfS	12
Impact of costs of hedging adjustment	(22)
Impairment provisions	(7)
Tax impact	1
Re-measurement of funds	1
Total impact	(15)
Ending balance	$ 23,746

New Standards and Interpretat_8

New Standards and Interpretations Adopted in the Current Year - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Disclosure of initial application of standards or interpretations [Line Items]
Reclassification of retained earnings to cost of hedging reserve	$ 22
Reclassification of cash flow hedge reserve to cost of hedging reserve	4
Transition adjustment reduction in trade and other receivables				$ 235
Transition adjustment reduction in deferred tax liabilities				71
Consolidated sales revenue	40,522	$ 40,030	$ 33,781
Increase (decrease) due to changes in accounting policy required by IFRSs [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Consolidated sales revenue	$ (19)
Retained earnings [Member]
Disclosure of initial application of standards or interpretations [Line Items]
De-recognition of receivable arising from uplift transaction				164
Transition adjustment reduction in trade and other receivables				235
Bottom of range [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Period to determine final prices for copper concentrate	30 days
Top of range [Member]
Disclosure of initial application of standards or interpretations [Line Items]
Period to determine final prices for copper concentrate	180 days
IFRS 9 [member]
Disclosure of initial application of standards or interpretations [Line Items]
Impairment provision resulting from the application of the ECL model				$ 7

Rio Tinto financial informati_3

Rio Tinto financial information by business unit - Schedule of financial information by business unit (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2018USD ($)	Dec. 31, 2018USD ($)Employee	Dec. 31, 2017USD ($)Employee	Dec. 31, 2016USD ($)Employee	Jan. 01, 2018USD ($)
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 40,522	$ 40,030	$ 33,781
Proft on ordinary activities before finance items and tax		18,200	14,474	7,116
Depreciation & amortisation in subsidiaries excluding capitalised depreciation		(3,909)	(4,302)	(4,691)
Impairment charges		(132)	(796)	(249)
Net earnings		13,638	8,762	4,617
Capital expenditure		4,844	4,344	2,658
Depreciation and amortisation expense proportionately consolidated		4,015	4,375	4,794
Operating assets		$ 43,431	$ 48,556	$ 48,877
Number of employees | Employee		47,758	46,807	51,018
Pre-tax gains on disposals of property, plant and equipment	$ 549	$ 586	$ 138	$ 354
Capital expenditure per cash flow statement		5,430	4,482	3,012
Net cash/(debt)		255	(3,845)	(9,587)
Equity attributable to owners of Rio Tinto (see Group balance sheet)		43,686	44,711	39,290	$ 44,542
Net assets/(liabilities) of disposal groups held for sale [Member]
Disclosure of operating segments [Line Items]
Operating assets		440	370	(7)
Diamonds [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		695	706	613
Reportable segments [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		42,850	41,872	35,329
Capital expenditure		5,279	4,691	3,355
Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		18,485	18,251	14,605
Proft on ordinary activities before finance items and tax		11,325	11,520	8,526
Net earnings		6,514	6,692	4,611
Capital expenditure		1,288	1,201	868
Depreciation and amortisation expense proportionately consolidated		1,682	1,645	1,645
Operating assets		$ 14,488	$ 16,537	$ 16,359
Number of employees | Employee		10,422	10,159	10,424
Reportable segments [Member] | Iron Ore [Member] | Evaluation projects/other [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 126	$ 108	$ 75
Proft on ordinary activities before finance items and tax		58	137	(32)
Net earnings		54	116	(51)
Operating assets		2	2	2
Reportable segments [Member] | Aluminium [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		12,191	11,005	9,458
Proft on ordinary activities before finance items and tax		3,095	3,423	2,472
Net earnings		1,347	1,583	947
Capital expenditure		1,373	1,436	916
Depreciation and amortisation expense proportionately consolidated		1,122	1,199	1,250
Operating assets		$ 16,446	$ 16,346	$ 15,782
Number of employees | Employee		13,640	13,345	14,037
Reportable segments [Member] | Aluminium [Member] | Intrasegment [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ (861)	$ (790)	$ (786)
Proft on ordinary activities before finance items and tax		(7)	(25)
Net earnings		(5)	(17)
Operating assets		(20)	(18)
Reportable segments [Member] | Aluminium [Member] | Inter-segment and other [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		(3,226)	(2,321)	(1,822)
Proft on ordinary activities before finance items and tax		(88)	(19)	(50)
Net earnings		(67)	(12)	(13)
Capital expenditure			5	1
Depreciation and amortisation expense proportionately consolidated		(1)	6	25
Operating assets		$ 789	$ 772	$ 171
Number of employees | Employee		180	222	231
Reportable segments [Member] | Aluminium [Member] | Integrated operations [Member]
Disclosure of operating segments [Line Items]
Capital expenditure		$ 1,881	$ 1,436	$ 916
Depreciation and amortisation expense proportionately consolidated		1,122	1,199	1,250
Operating assets		$ 16,446	$ 16,346	$ 15,782
Number of employees | Employee		13,640	13,345	14,037
Reportable segments [Member] | Aluminium [Member] | Other product group items [Member]
Disclosure of operating segments [Line Items]
Capital expenditure		$ (508)
Reportable segments [Member] | Aluminium [Member] | Evaluation projects/other [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		126	$ 109	$ 76
Proft on ordinary activities before finance items and tax		137	126	167
Net earnings		122	115	154
Reportable segments [Member] | Aluminium [Member] | Bauxite [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		2,324	2,019	1,913
Proft on ordinary activities before finance items and tax		790	804	848
Net earnings		412	463	493
Capital expenditure		953	825	343
Depreciation and amortisation expense proportionately consolidated		165	123	110
Operating assets		$ 2,494	$ 1,897	$ 1,278
Number of employees | Employee		2,676	2,534	2,592
Reportable segments [Member] | Aluminium [Member] | Alumina [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 3,340	$ 2,661	$ 2,118
Proft on ordinary activities before finance items and tax		1,137	454	27
Net earnings		634	180	(121)
Capital expenditure		218	108	87
Depreciation and amortisation expense proportionately consolidated		194	209	206
Operating assets		$ 2,721	$ 2,733	$ 2,588
Number of employees | Employee		2,009	2,012	2,139
Reportable segments [Member] | Aluminium [Member] | Bauxite & Alumina [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 4,803	$ 3,890	$ 3,245
Proft on ordinary activities before finance items and tax		1,920	1,233	875
Net earnings		1,041	626	372
Capital expenditure		1,171	933	430
Depreciation and amortisation expense proportionately consolidated		359	332	316
Operating assets		$ 5,195	$ 4,612	$ 3,866
Number of employees | Employee		4,685	4,546	4,731
Reportable segments [Member] | Aluminium [Member] | Primary Metal [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 6,468	$ 5,808	$ 4,913
Proft on ordinary activities before finance items and tax		1,418	1,762	1,258
Net earnings		595	778	402
Capital expenditure		595	389	394
Depreciation and amortisation expense proportionately consolidated		615	665	716
Operating assets		$ 9,306	$ 9,946	$ 10,701
Number of employees | Employee		6,497	6,404	6,799
Reportable segments [Member] | Aluminium [Member] | Pacific Aluminium [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 2,541	$ 2,305	$ 1,971
Proft on ordinary activities before finance items and tax		148	453	264
Net earnings			176	62
Capital expenditure		115	109	91
Depreciation and amortisation expense proportionately consolidated		149	196	193
Operating assets		$ 1,156	$ 1,016	$ 1,044
Number of employees | Employee		2,278	2,173	2,276
Reportable segments [Member] | Aluminium [Member] | Integrated operations [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 10,586	$ 9,682	$ 8,307
Proft on ordinary activities before finance items and tax		3,398	3,429	2,347
Net earnings		1,569	1,568	823
Reportable segments [Member] | Aluminium [Member] | Other product group items [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		1,479	1,214	1,075
Proft on ordinary activities before finance items and tax		(440)	(132)	(42)
Net earnings		(344)	(100)	(30)
Reportable segments [Member] | Aluminium [Member] | Product group operations [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		12,065	10,896	9,382
Proft on ordinary activities before finance items and tax		2,958	3,297	2,305
Net earnings		1,225	1,468	793
Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		6,468	4,842	4,524
Proft on ordinary activities before finance items and tax		2,776	1,904	1,387
Net earnings		1,054	263	(18)
Capital expenditure		2,150	1,622	1,441
Depreciation and amortisation expense proportionately consolidated		1,317	1,452	1,601
Operating assets		$ 11,389	$ 11,743	$ 11,530
Number of employees | Employee		8,671	8,354	9,489
Reportable segments [Member] | Copper & Diamonds [member] | Evaluation projects/other [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		$ (267)	$ (205)	$ (190)
Net earnings		(149)	(99)	(95)
Capital expenditure		11	1	(2)
Depreciation and amortisation expense proportionately consolidated		5	5	4
Operating assets		$ 129	$ 135	$ 166
Number of employees | Employee		146	142	127
Reportable segments [Member] | Copper & Diamonds [member] | Product group operations [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 6,468	$ 4,842	$ 4,524
Proft on ordinary activities before finance items and tax		3,043	2,109	1,577
Net earnings		1,203	362	77
Capital expenditure		2,139	1,621	1,443
Depreciation and amortisation expense proportionately consolidated		1,312	1,447	1,597
Operating assets		$ 11,260	$ 11,608	$ 11,364
Number of employees | Employee		8,525	8,212	9,362
Reportable segments [Member] | Copper & Diamonds [member] | Diamonds [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 695	$ 706	$ 613
Proft on ordinary activities before finance items and tax		301	287	239
Net earnings		118	92	47
Capital expenditure		64	85	97
Depreciation and amortisation expense proportionately consolidated		118	132	164
Operating assets		$ 267	$ 441	$ 655
Number of employees | Employee		967	922	907
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 5,697	$ 7,764	$ 6,734
Proft on ordinary activities before finance items and tax		2,193	2,803	1,806
Net earnings		1,012	1,242	612
Capital expenditure		456	467	141
Depreciation and amortisation expense proportionately consolidated		475	652	739
Operating assets		$ 3,861	$ 6,313	$ 7,049
Number of employees | Employee		10,106	10,864	13,453
Reportable segments [Member] | Energy & Minerals [Member] | Evaluation projects/other [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 60	$ 43	$ 22
Proft on ordinary activities before finance items and tax		(52)	(9)	(31)
Net earnings		(37)	(7)	(25)
Capital expenditure				4
Depreciation and amortisation expense proportionately consolidated				1
Operating assets		$ 41	$ 41	$ 38
Number of employees | Employee		33	25	763
Reportable segments [Member] | Energy & Minerals [Member] | Product group operations [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 5,637	$ 7,721	$ 6,712
Proft on ordinary activities before finance items and tax		2,260	2,825	1,939
Net earnings		1,056	1,255	684
Capital expenditure		456	467	137
Depreciation and amortisation expense proportionately consolidated		475	652	738
Operating assets		$ 3,805	$ 6,255	$ 6,998
Number of employees | Employee		10,003	10,829	12,055
Reportable segments [Member] | Energy & Minerals [Member] | Uranium [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 415	$ 417	$ 456
Proft on ordinary activities before finance items and tax		18	15	54
Net earnings		(4)	(26)	10
Capital expenditure		8	21	30
Depreciation and amortisation expense proportionately consolidated		4	37	25
Operating assets		$ (406)	$ (327)	$ (143)
Number of employees | Employee		1,324	1,307	1,303
Reportable segments [Member] | Other operations [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 9	$ 10	$ 8
Proft on ordinary activities before finance items and tax		(70)	(116)	(95)
Net earnings		(102)	(138)	(88)
Capital expenditure		12	(35)	(11)
Depreciation and amortisation expense proportionately consolidated		26	32	34
Operating assets		$ (442)	$ (328)	$ 203
Number of employees | Employee		187	203	249
Inter-segment transactions [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ (15)	$ (15)	$ (11)
Operating assets		129	206	142
Product group [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		42,835	41,857	35,318
Proft on ordinary activities before finance items and tax		19,319	19,534	14,096
Net earnings		9,825	9,642	6,064
Capital expenditure		5,279	4,691	3,355
Depreciation and amortisation expense proportionately consolidated		4,622	4,980	5,269
Operating assets		$ 45,742	$ 50,611	$ 50,923
Number of employees | Employee		43,026	42,925	47,652
Central pension costs, share-based payments and insurance [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		$ (128)	$ (68)	$ (34)
Net earnings		(90)	(48)	(24)
Restructuring, Project and One-Off Costs [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		(272)	(177)	(13)
Net earnings		(190)	(124)	(9)
Central Costs [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		(552)	(491)	(364)
Net earnings		(410)	(311)	(208)
Exploration and evaluation [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		(231)	(218)	(175)
Net earnings		(193)	(178)	(147)
Net interest [Member]
Disclosure of operating segments [Line Items]
Net earnings		(134)	(354)	(576)
Underlying earnings [member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		18,136	18,580	13,510
Net earnings		8,808	8,627	5,100
Items excluded from underlying earnings [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue			10	18
Proft on ordinary activities before finance items and tax		5,127	1,912	(687)
Net earnings		4,830	135	(483)
EBITDA and Net Earnings [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		23,263	20,492	12,823
Net earnings		13,638	8,762	4,617
Capital expenditure of equity accounted units
Disclosure of operating segments [Line Items]
Adjustment for equity accounted units revenue		(2,313)	(1,837)	(1,555)
Depreciation and amortisation in equity accounted units		650	648	526
Taxation and finance items in equity accounted units		(372)	(272)	(241)
Capital expenditure		(500)	(417)	(651)
Depreciation and amortisation expense proportionately consolidated		(650)	(647)	(526)
Other items [Member]
Disclosure of operating segments [Line Items]
Capital expenditure		65	70	(46)
Depreciation and amortisation expense proportionately consolidated		43	42	51
Operating assets		$ (2,880)	$ (2,631)	$ (2,181)
Number of employees | Employee		4,432	3,882	3,377
Oyu Tolgoi and Turquoise Hill [Member] | Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 1,180	$ 940	$ 1,203
Proft on ordinary activities before finance items and tax		375	256	436
Net earnings		69	36	52
Capital expenditure		1,284	901	322
Depreciation and amortisation expense proportionately consolidated		219	344	450
Operating assets		$ 6,072	$ 4,725	$ 3,804
Number of employees | Employee		2,863	2,835	2,728
Grasberg Joint Venture | Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 457	$ 33
Proft on ordinary activities before finance items and tax		281	(3)	$ (17)
Net earnings		217	(169)	(64)
Capital expenditure		171	138	174
Depreciation and amortisation expense proportionately consolidated		$ 30	42	89
Operating assets			$ 1,137	$ 1,151
Number of employees | Employee		1,615	1,642	2,859
Pilbara [member] | Reportable segments [Member] | Iron Ore [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 18,359	$ 18,143	$ 14,530
Proft on ordinary activities before finance items and tax		11,267	11,383	8,558
Net earnings		6,460	6,576	4,662
Capital expenditure		1,288	1,201	868
Depreciation and amortisation expense proportionately consolidated		1,682	1,645	1,645
Operating assets		$ 14,486	$ 16,535	$ 16,357
Number of employees | Employee		10,422	10,159	10,424
Rio Tinto Kennecott [Member] | Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary		100.00%
Consolidated sales revenue		$ 1,862	$ 1,352	$ 1,243
Proft on ordinary activities before finance items and tax		785	539	126
Net earnings		293	78	(228)
Capital expenditure		318	249	333
Depreciation and amortisation expense proportionately consolidated		427	422	530
Operating assets		$ 1,864	$ 1,936	$ 2,189
Number of employees | Employee		1,993	1,734	1,638
Escondida [Member] | Reportable segments [Member] | Copper & Diamonds [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary		30.00%
Consolidated sales revenue		$ 2,274	$ 1,811	$ 1,465
Proft on ordinary activities before finance items and tax		1,301	1,030	793
Net earnings		506	325	270
Capital expenditure		302	248	517
Depreciation and amortisation expense proportionately consolidated		518	507	364
Operating assets		$ 3,057	$ 3,369	$ 3,565
Number of employees | Employee		1,087	1,079	1,230
Rio Tinto Coal Australia | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 989	$ 2,829	$ 2,634
Proft on ordinary activities before finance items and tax		893	1,223	893
Net earnings		591	716	382
Capital expenditure		32	84	(107)
Depreciation and amortisation expense proportionately consolidated		34	152	297
Operating assets		$ (837)	$ 1,040	$ 1,807
Number of employees | Employee		1,005	1,924	3,049
Iron Ore Company of Canada [member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 1,561	$ 1,867
Net earnings		176	221
Equity attributable to owners of Rio Tinto (see Group balance sheet)		$ 994	1,153
Iron Ore Company of Canada [member] | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary		58.70%
Consolidated sales revenue		$ 1,583	1,867	$ 1,324
Proft on ordinary activities before finance items and tax		586	770	335
Net earnings		166	235	64
Capital expenditure		189	202	75
Depreciation and amortisation expense proportionately consolidated		154	157	151
Operating assets		$ 975	$ 988	$ 1,018
Number of employees | Employee		2,397	2,382	2,308
Rio Tinto Iron Titanium | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Consolidated sales revenue		$ 1,782	$ 1,763	$ 1,419
Proft on ordinary activities before finance items and tax		510	546	370
Net earnings		174	201	86
Capital expenditure		169	119	97
Depreciation and amortisation expense proportionately consolidated		201	219	189
Operating assets		$ 3,390	$ 3,881	$ 3,662
Number of employees | Employee		4,058	4,048	4,094
Rio Tinto Borates [Member] | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary		100.00%
Consolidated sales revenue		$ 622	$ 630	$ 620
Proft on ordinary activities before finance items and tax		197	244	213
Net earnings		111	126	117
Capital expenditure		44	28	31
Depreciation and amortisation expense proportionately consolidated		62	65	53
Operating assets		$ 518	$ 523	$ 508
Number of employees | Employee		980	936	984
Dampier Salt [member] | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary		68.40%
Consolidated sales revenue		$ 246	$ 215	$ 259
Proft on ordinary activities before finance items and tax		56	27	74
Net earnings		18	3	25
Capital expenditure		14	13	11
Depreciation and amortisation expense proportionately consolidated		20	22	23
Operating assets		$ 165	$ 150	$ 146
Number of employees | Employee		239	232	317
Simandou Iron Ore Project | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Proft on ordinary activities before finance items and tax		$ (15)	$ (13)	$ (102)
Net earnings		(7)	(6)	(47)
Operating assets		$ 15	$ 17	$ 13
Number of employees | Employee		70	10	635

Rio Tinto financial informati_4

Rio Tinto financial information by business unit - Schedule of financial information by business unit (Parenthetical) (Detail) - USD ($) $ in Millions	Aug. 01, 2018	Jun. 01, 2018	Sep. 01, 2017	Sep. 01, 2017	Aug. 05, 2016	Feb. 03, 2016	Jun. 01, 2018	Aug. 01, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of operating segments [Line Items]
Proceeds from sale of surplus land									$ 508
Proceeds from issue of equity to non-controlling interests									85	$ 170	$ 101
Operating assets									$ 43,431	48,556	48,877
Capital expenditure percentage of subsidiaries									100.00%
Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Operating assets									$ 3,861	6,313	$ 7,049
Australia [Member]
Disclosure of operating segments [Line Items]
Proceeds from disposal of ownership in joint venture	$ 1,700
Mount Pleasant Thermal Coal Project [Member] | MACH Energy Australia Pty Ltd [Member]
Disclosure of operating segments [Line Items]
Proceeds from disposal capital expenditure					$ 192
Ownership interest in cash generating units disposed					100.00%
Hope Downs Joint Venture [member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture									50.00%
Robe river iron associates [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									65.00%
Percentage of ownership interest exchanged in joint venture									65.00%
Proportion of net beneficial interest									53.00%
Non-controlling interest (%), Subsidiary									12.00%
Freeport-McMoRan Inc [Member]
Disclosure of operating segments [Line Items]
Percentage of material mined									40.00%
Diavik Joint Venture [member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture									60.00%
Hail Creek [Member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture								82.00%
Hail Creek [Member] | Australia [Member]
Disclosure of operating segments [Line Items]
Ownership interest in joint venture disposed	82.00%
Kestrel Underground Coal Mine [Member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture								80.00%
Winchester South [Member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture							80.00%
Winchester South [Member] | Australia [Member]
Disclosure of operating segments [Line Items]
Ownership interest in joint venture disposed		75.00%
Proceeds from disposal of ownership in joint venture		$ 200
Valeria Development Projects [Member]
Disclosure of operating segments [Line Items]
Percentage of ownership interest exchanged in joint venture								80.00%
Valeria Development Projects [Member] | Australia [Member]
Disclosure of operating segments [Line Items]
Ownership interest in joint venture disposed	71.20%
Kestrel Underground Coal Mine [Member] | Australia [Member]
Disclosure of operating segments [Line Items]
Ownership interest in joint venture disposed	80.00%
Proceeds from disposal of ownership in joint venture	$ 2,250
30 Percent [Member] | Robe river iron associates [member]
Disclosure of operating segments [Line Items]
Net beneficial interest held percentage									30.00%
Net beneficial interest held percentage as owned subsidiary									60.00%
35 Percent [Member] | Robe river iron associates [member]
Disclosure of operating segments [Line Items]
Net beneficial interest held percentage									35.00%
Net beneficial interest held percentage as owned subsidiary									100.00%
Hamersley Iron Pty Limited [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									100.00%
Hamersley Iron Pty Limited [member] | Ordinary shares [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									100.00%
Oyu Tolgoi LLC [member] | Turquoise Hill Resources Ltd [member]
Disclosure of operating segments [Line Items]
Percentage of share class held in subsidiaries									50.80%
Oyu Tolgoi LLC [member] | Turquoise Hill Resources Ltd [member] | Oyo Tolgoi Copper-Gold Mine [Member]
Disclosure of operating segments [Line Items]
Percentage of share class held in subsidiaries									66.00%
Argyle Diamonds Limited [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									100.00%
Argyle Diamonds Limited [member] | Ordinary shares [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									100.00%
Coal & Allied Industries Limited [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary						100.00%					80.00%
Ownership interest in joint venture disposed			100.00%
Proportion Of Ownership Interest In Subsidiary Disposed				100.00%
Proceeds from issue of equity to non-controlling interests				$ 2,690
Rio Tinto Coal Australia | Reportable segments [Member] | Energy & Minerals [Member]
Disclosure of operating segments [Line Items]
Operating assets									$ (837)	$ 1,040	$ 1,807
Rio Tinto Fer et Titane Inc. [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									100.00%
QIT Madagascar Minerals SA [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									80.00%
Richards Bay Minerals [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									74.00%
Energy Resources of Australia Limited [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									68.40%
Energy Resources of Australia Limited [Member] | Ordinary shares [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									68.39%
Non-controlling interest (%), Subsidiary									31.61%
Rossing Uranium [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									68.60%
China national uranium corporation limited [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									68.60%
Simfer Jersey Limited [member] | Ordinary shares [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									53.00%
Non-controlling interest (%), Subsidiary									47.00%
Simfer S.A. [member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									85.00%
Non-controlling interest (%), Subsidiary									45.05%
Gove Alumina Refinery and Rio Tinto Marine [Member]
Disclosure of operating segments [Line Items]
Ownership percentage in subsidiary									100.00%