EXHIBIT 12.1

BOSTON PROPERTIES LIMITED PARTNERSHIP

CALCULATION OF RATIOS OF EARNINGS TO COMBINED FIXED CHARGES

AND PREFERRED DISTRIBUTIONS

Boston Properties Limited Partnerships ratios of earnings to combined fixed charges and preferred distributions for the five years ended December 31, 2005 were as follows:



|                                                                                                                                                                                                                                                                                                          |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |  | ----------------------- | ------- | - | ---- | - | ------- | ---- |  | - | ------- | - |  | ---- | ------- | - |  | - | ------- | -
|                                                                                                                                                                                                                                                                                                          |  | Year Ended December 31, |        
|                                                                                                                                                                                                                                                                                                          |  | 2005                    |         |   | 2004 |   |         | 2003 |  |   | 2002    |   |  | 2001 |        
|                                                                                                                                                                                                                                                                                                          |  | (dollars in thousands)  |        
|Earnings:                                                                                                                                                                                                                                                                                                 |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Add:                                                                                                                                                                                                                                                                                                      |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Income before minority interests in property partnerships, income from unconsolidated joint ventures, gains on sales of real estate and other
assets, discontinued operations, cumulative effect of a change in accounting principle and preferred distributions and allocation of undistributed earnings |  | $                       | 306,971 |   |      | $ | 306,589 |      |  | $ | 289,575 |   |  | $    | 264,425 |   |  | $ | 231,056 |  
|Gains on sales of real estate and other assets                                                                                                                                                                                                                                                            |  |                         | 188,546 |   |      |   | 9,822   |      |  |   | 70,627  |   |  |      | 233,304 |   |  |   | 11,238  |  
|Amortization of interest capitalized                                                                                                                                                                                                                                                                      |  |                         | 3,298   |   |      |   | 2,845   |      |  |   | 2,640   |   |  |      | 2,526   |   |  |   | 950     |  
|Distributions from unconsolidated joint ventures                                                                                                                                                                                                                                                          |  |                         | 7,179   |   |      |   | 6,663   |      |  |   | 8,412   |   |  |      | 8,692   |   |  |   | 2,735   |  
|Combined fixed charges and preferred distributions (see below)                                                                                                                                                                                                                                            |  |                         | 340,589 |   |      |   | 334,082 |      |  |   | 342,244 |   |  |      | 316,835 |   |  |   | 306,709 |  
|Subtract:                                                                                                                                                                                                                                                                                                 |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Interest capitalized                                                                                                                                                                                                                                                                                      |  |                         | (5,718  | ) |      |   | (10,849 | )    |  |   | (19,200 | ) |  |      | (22,510 | ) |  |   | (59,292 | )
|Preferred distributions                                                                                                                                                                                                                                                                                   |  |                         | (26,780 | ) |      |   | (17,063 | )    |  |   | (23,608 | ) |  |      | (31,258 | ) |  |   | (36,026 | )
|                                                                                                                                                                                                                                                                                                          |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Total earnings                                                                                                                                                                                                                                                                                            |  | $                       | 814,085 |   |      | $ | 632,089 |      |  | $ | 670,690 |   |  | $    | 772,014 |   |  | $ | 457,370 |  
|                                                                                                                                                                                                                                                                                                          |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Combined fixed charges and preferred distributions:                                                                                                                                                                                                                                                       |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Interest expensed                                                                                                                                                                                                                                                                                         |  | $                       | 308,091 |   |      | $ | 306,170 |      |  | $ | 299,436 |   |  | $    | 263,067 |   |  | $ | 211,391 |  
|Interest capitalized                                                                                                                                                                                                                                                                                      |  |                         | 5,718   |   |      |   | 10,849  |      |  |   | 19,200  |   |  |      | 22,510  |   |  |   | 59,292  |  
|Preferred distributions                                                                                                                                                                                                                                                                                   |  |                         | 26,780  |   |      |   | 17,063  |      |  |   | 23,608  |   |  |      | 31,258  |   |  |   | 36,026  |  
|                                                                                                                                                                                                                                                                                                          |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Total combined fixed charges and preferred distributions                                                                                                                                                                                                                                                  |  | $                       | 340,589 |   |      | $ | 334,082 |      |  | $ | 342,244 |   |  | $    | 316,835 |   |  | $ | 306,709 |  
|                                                                                                                                                                                                                                                                                                          |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  
|Ratio of earnings to combined fixed charges and preferred distributions                                                                                                                                                                                                                                   |  |                         | 2.39    |   |      |   | 1.89    |      |  |   | 1.96    |   |  |      | 2.44    |   |  |   | 1.49    |  
|                                                                                                                                                                                                                                                                                                          |  |                         |         |   |      |   |         |      |  |   |         |   |  |      |         |   |  |   |         |  

The ratio of earnings to combined fixed charges and preferred distributions was computed by
dividing earnings by combined fixed charges and preferred distributions. Earnings consist of income before minority interests in property partnerships, income from unconsolidated joint ventures, discontinued operations, cumulative effect of a change
in accounting principle and preferred distributions and allocation of undistributed earnings, plus amortization of interest capitalized, distributions from unconsolidated joint ventures, and combined fixed charges and preferred distributions, minus
interest capitalized and preferred distributions. Combined fixed charges and preferred distributions consist of interest expensed, which includes credit enhancement fees and amortization of loan costs, interest capitalized, and preferred
distributions.