<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, 1998    December 31, 1997    December 31, 1996
                                                                     -----------------    -----------------    ------------------
<S>                                                                       <C>                   <C>                  <C>
EARNINGS AS DEFINED (1)
Net Income .......................................................        $114,619              $125,630             $122,239
Fixed charges ....................................................          61,304                57,905               53,831
                                                                          --------              --------             --------
  Earnings as defined ............................................        $175,923              $183,535             $176,070
                                                                          ========              ========             ========
                                                                                                                    
FIXED CHARGES AS DEFINED (1)                                                                                        
Interest on long-term debt .......................................        $ 47,091              $ 47,024             $ 43,163
Interest on other borrowed funds .................................          12,113                 8,664                8,012
Amortization of debt discounts, premium                                                                             
  and expense ....................................................             955                 1,032                1,081
Interest implicit in rentals (2) .................................           1,145                 1,185                1,575
                                                                          --------              --------             --------
  Fixed charges as defined .......................................        $ 61,304              $ 57,905             $ 53,831
                                                                          ========              ========             ========
                                                                                                                    
Ratio of Earnings to Fixed Charges ...............................            2.87                  3.17                 3.27
                                                                          ========              ========             ========
----------------
</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.