| Document and Entity Information - USD ($) $ in Billions | Dec. 31, 2021 | Feb. 18, 2022 | Jun. 30, 2021 |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | false | ||
| Document Annual Report | true | ||
| Document Period End Date | Dec. 31, 2021 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Document Fiscal Year Focus | 2021 | ||
| Document Fiscal Period Focus | FY | ||
| Document Transition Report | false | ||
| Entity File Number | 001-39592 | ||
| Entity Registrant Name | Kronos Bio, Inc. | ||
| Entity Central Index Key | 0001741830 | ||
| Entity Incorporation, State or Country Code | DE | ||
| Entity Tax Identification Number | 82-1895605 | ||
| Entity Address, Address Line One | 1300 So. El Camino Real | ||
| Entity Address, Address Line Two | Suite 400 | ||
| Entity Address, City or Town | San Mateo | ||
| Entity Address, State or Province | CA | ||
| Entity Address, Postal Zip Code | 94402 | ||
| City Area Code | 650 | ||
| Local Phone Number | 781-5200 | ||
| Title of 12(b) Security | Common stock, $0.001 par value per share | ||
| Trading Symbol | KRON | ||
| Security Exchange Name | NASDAQ | ||
| Entity Well-known Seasoned Issuer | No | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Small Business | false | ||
| Entity Emerging Growth Company | false | ||
| ICFR Auditor Attestation Flag | true | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 1.3 | ||
| Entity Common Stock, Shares Outstanding | 56,601,965 | ||
| Auditor Firm ID | 42 | ||
| Auditor Name | Ernst & Young LLP | ||
| Auditor Location | Redwood City, California |
