<Page>
EXHIBIT 12.1
BOSTON PROPERTIES LIMITED PARTNERSHIP
CALCULATION OF RATIO OF EARNINGS TO FIXED CHARGES
Boston Properties Limited Partnership's ratios of earnings to fixed charges for
the five years ended December 31, 2002 were as follows:
<Table>
<Caption>
Year Ended December 31,
-------------------------------------------------------
2002 2001 2000 1999 1998
--------- --------- --------- --------- ---------
(dollars in thousands)
Earnings:
Add:
Income before minority interests in property
partnerships, income from unconsolidated joint ventures,
gains (losses) on sales of real estate and land held
for development, discontinued operations, extraordinary
items, cumulative effect of a change in accounting principle
and preferred distributions $ 297,721 $ 272,349 $ 225,014 $ 178,554 $ 137,739
Gains (losses) on sales of real estate and land held for
development 233,304 11,238 (313) 8,735 --
Amortization of interest capitalized 2,526 950 415 153 22
Distributions from unconsolidated joint ventures 8,692 2,735 1,848 972 --
Fixed charges (see below) 325,453 318,707 287,771 254,474 137,556
Subtract:
Interest capitalized (22,510) (59,292) (37,713) (16,953) (6,933)
Preferred distributions (31,228) (36,026) (32,994) (32,111) (5,830)
--------- --------- --------- --------- ---------
Total earnings $ 813,928 $ 510,661 $ 444,028 $ 393,824 $ 262,554
========= ========= ========= ========= =========
Fixed charges:
Interest expensed $ 271,685 $ 223,389 $ 217,064 $ 205,410 $ 124,793
Interest capitalized 22,510 59,292 37,713 16,953 6,933
Preferred distributions 31,258 36,026 32,994 32,111 5,830
--------- --------- --------- --------- ---------
Total fixed charges $ 325,453 $ 318,707 $ 287,771 $ 254,474 $ 137,556
========= ========= ========= ========= =========
--------- --------- --------- --------- ---------
Ratio of earnings to fixed charges 2.50 1.60 1.54 1.55 1.91
========= ========= ========= ========= =========
</Table>
The ratio of earnings to fixed charges was computed by dividing earnings by
fixed charges. Earnings consist of income before minority interests in property
partnerships, income from unconsolidated joint ventures, discontinued
operations, extraordinary items, cumulative effect of a change in accounting
principle and preferred distributions, plus amortization of interest
capitalized, distributions from unconsolidated joint ventures, fixed charges,
minus interest capitalized and preferred distributions. Fixed charges consist of
interest expensed, which includes credit enhancement fees and amortization of
loan costs, interest capitalized, and preferred distributions.