<PAGE>   1
                                                                      EXHIBIT 12

                           LONE STAR INDUSTRIES, INC.

         Statement Re Computation of Ratio of Earnings to Fixed Charges
                          (Dollar amounts in thousands)


<TABLE>
<CAPTION>
                                                                                                  Successor Company             

                                                                                                                                
                                                                          For the             For the           For the Nine    
                                                                        Year Ended          Year Ended          Months Ended    
                                                                     December 31, 1996   December 31, 1995   December 31, 1994  
                                                                     -----------------   -----------------   -----------------  

<S>                                                                  <C>                 <C>                 <C>                
Continuing Operations:

Earnings Available:

          Income (loss) before provision
                   for income taxes                                      $ 81,770            $ 53,376            $ 45,133       
                                                                                                                                
          Less:    Excess of earnings over dividends                                                                            
                   of less than fifty percent owned                                                                             
                   companies                                                    0              (2,978)               (674)      
                                                                                                                                
                   Capitalized interest                                    (1,325)               (262)               (168)      
                                                                                                                                
                                                                         --------            --------            --------       
                                                                         $ 80,445            $ 50,136            $ 44,291       
                                                                         ========            ========            ========       
Fixed Charges:                                                                                                                  
                                                                                                                                
          Interest expense (including capitalized                                                                               
                   interest) and amortization of debt discount                                                                  
                   and expenses                                          $  7,931            $  9,358            $  6,980       
                                                                                                                                
          Portion of rent expense representative of an                                                                          
                   interest factor                                          1,079               1,636               1,631       
                                                                                                                                
                                                                         --------            --------            --------       
Total Fixed Charges                                                         9,010              10,994               8,611       
                                                                                                                                
                                                                         --------            --------            --------       
Total Earnings Available                                                 $ 89,455            $ 61,130            $ 52,902       
                                                                         ========            ========            ========       
                                                                                                                                
                                                                                                                                
Ratio of Earnings to Fixed Charges (1)                                       9.93                5.56                6.14       
                                                                         ========            ========            ========       
                                                                                                                                
Earnings deficiency                                                      $      0            $      0            $      0       
                                                                         ========            ========            ========       
                                                                                                                                


<CAPTION>
                                                                                              Predecessor Company    
                                                                                                                     
                                                                                                 For the Year        
                                                                       For the Three           Ended December 31,    
                                                                       Months Ended         ------------------------ 
                                                                      March 31, 1994          1993            1992   
                                                                      --------------        --------        -------- 
                                                                                                                     
<S>                                                                   <C>                   <C>             <C>      
Continuing Operations:                                                                                               
                                                                                                                     
Earnings Available:                                                                                                  
                                                                                                                     
          Income (loss) before provision                                                                             
                   for income taxes                                      $(3,170)           $  6,196        $(42,429)
                                                                                                                     
          Less:    Excess of earnings over dividends                                                                 
                   of less than fifty percent owned                                                                  
                   companies                                                 (75)                  0            (294)
                                                                                                                     
                   Capitalized interest                                      (38)               (195)           (196)
                                                                                                                     
                                                                         -------            --------        -------- 
                                                                         $(3,283)           $  6,001        $(42,919)
                                                                         =======            ========        ======== 
Fixed Charges:                                                                                                       
                                                                                                                     
          Interest expense (including capitalized                                                                    
                   interest) and amortization of debt discount                                                       
                   and expenses                                          $   271            $  1,832        $  2,406 
                                                                                                                     
          Portion of rent expense representative of an                                                               
                   interest factor                                           252               1,963           2,108 
                                                                                                                     
                                                                         -------            --------        -------- 
Total Fixed Charges                                                          523               3,795           4,514 
                                                                                                                     
                                                                         -------            --------        -------- 
Total Earnings Available                                                 $(2,760)           $  9,796        $(38,405)
                                                                         =======            ========        ======== 
                                                                                                                     
                                                                                                                     
Ratio of Earnings to Fixed Charges (1)                                     n/m                  2.58           n/m   
                                                                         =======            ========        ======== 
                                                                                                                     
Earnings deficiency                                                      $(3,283)           $      0        $(42,919)
                                                                         =======            ========        ======== 
</TABLE>


(1)  Any ratio with a value less than one is not meaningful to the exhibit, and
     therefore is not disclosed.