<PAGE>
 
                                                                      Exhibit 11
                                                                      ----------

                    WINDSOR REAL ESTATE INVESTMENT TRUST 8
                    --------------------------------------
                 COMPUTATION OF NET LOSS PER COMMON SHARE (1)
                 ----------------------------------------    

<TABLE>
<CAPTION>
                             Three Months Ended              Nine Months
                                September 30,             Ended September 30,
                         --------------------------   --------------------------
                         
                             1997          1996           1997          1996
                         ------------  ------------   ------------  ------------
                         
<S>                      <C>           <C>            <C>           <C> 
Net gain (loss)            $ (1,200)     $ (41,200)    $ (18,100)    $ (82,000)
 Less:                   
   Dividends paid        
    Preferred               (36,800)      (36,800)      (110,300)     (110,300)
    Common                  (33,800)      (33,800)      (101,400)     (101,400)
                           --------     ---------      ---------     ---------
                         
Overdistributed Earnings   $(71,800)    $(111,800)     $(229,800)    $(293,700)
                           ========     =========      =========     =========
                         
Allocation of            
-------------            
 Overdistributed         
 ---------------         
 Earnings (2)            
 ------------            
  Preferred                $(37,300)    $ (58,200)     $(119,500)    $(122,700)
  Common                    (34,500)      (53,600)      (110,300)     (112,500)
                           --------     ---------      ---------     ---------
                         
                           $(71,800)    $(111,800)     $(229,800)    $(235,200)
                           ========     =========      =========     =========
                         
Earnings Per             
------------             
 Common Share            
 ------------            
  Dividends Paid           $ 33,800     $ 33,800       $ 101,400     $ 101,400
  Allocation of          
   Overdistributed       
   Earnings                 (34,500)     (53,600)       (110,300)     (140,700)
                           --------     ---------      ---------     ---------
                         
Net Loss Attributable to 
 Common Shares             $   (700)    $(19,800)      $  (8,900)    $ (39,300)
                           ========     ========       =========     =========
                         
Weighted Average         
 Common Shares           
 Outstanding                 90,169       90,169          90,169        90,169
                           ========     ========       =========     =========
Net Loss                 
 Per Common              
 Share                     $  (0.01)    $  (0.22)      $   (0.10)    $   (0.44)
                           ========     ========       =========     =========
</TABLE>

Note
----

(1)  Net loss per common share is computed using the two class method.
(2)  Overdistributed earnings are allocated evenly, on a per share basis,
     between common and preferred shares.

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