<PAGE>   1
                                                                    EXHIBIT 12-1


               MICHIGAN CONSOLIDATED GAS COMPANY AND SUBSIDIARIES
                COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES
                             (THOUSANDS OF DOLLARS)


<TABLE>
<CAPTION>
                                                     Twelve Months Ended        Twelve Months Ended       Twelve Months Ended
                                                       December 31, 1997          December 31, 1996         December 31, 1995
                                                     -------------------        -------------------       -------------------
<S>                                                  <C>                        <C>                       <C>
EARNINGS AS DEFINED (1)
Net Income .................................              $125,630                     $122,239                 $112,727
Fixed charges ..............................                57,905                       53,831                   45,637
                                                          --------                     --------                 --------
  Earnings as defined ......................              $183,535                     $176,070                 $158,364
                                                          ========                     ========                 ========
                                                                                                                        
FIXED CHARGES AS DEFINED (1)                                                                                            
Interest on long-term debt .................              $ 47,024                     $ 43,163                 $ 35,820
Interest on other borrowed funds ...........                 8,664                        8,012                    7,053
Amortization of debt discounts, premium                                                                                 
  and expense ..............................                 1,032                        1,081                      996
Interest implicit in rentals (2) ...........                 1,185                        1,575                    1,768
                                                          --------                     --------                 --------
  Fixed charges as defined .................              $ 57,905                     $ 53,831                 $ 45,637
                                                          ========                     ========                 ========
                                                                                                                        
Ratio of Earnings to Fixed Charges .........                  3.17                         3.27                     3.47
                                                          ========                     ========                 ========
</TABLE>

----------------
Notes: 

(1)  Earnings and fixed charges are defined and computed in accordance with Item
     503 of Regulation S-K.

(2)  This amount is estimated to be a reasonable approximation of the interest
     portion of rentals.

MichCon is a guarantor of certain other debt. Fixed charges related to such debt
are deemed to be immaterial and therefore have been excluded from the above
ratios.