<PAGE>
                                                                      EXHIBIT 12

                       WILLIAMS COMMUNICATIONS GROUP, INC.

               COMPUTATIONS OF RATIO OF EARNINGS TO FIXED CHARGES
               AND RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND
                      PREFERRED STOCK DIVIDEND REQUIREMENTS


<Table>
<Caption>
                                                                   SIX MONTHS ENDED
                                                                       JUNE 30,
                                                              --------------------------
                                                                 2002            2001
                                                              ----------      ----------
                                                                    (IN THOUSANDS)
<S>                                                           <C>             <C>
Earnings:
   Loss before income taxes                                   $ (575,518)     $ (495,566)
   Add:
     Interest expense -- net                                     171,739         201,073
     Rental expense representative of interest factor             46,256          60,210
     Minority interest in loss of consolidated subsidiary         (8,587)        (13,191)
     Equity losses                                                 1,712           9,208
                                                              ----------      ----------
        Total loss as adjusted plus fixed charges             $ (364,398)     $ (238,266)
                                                              ==========      ==========
Fixed charges and combined fixed charges and
   preferred stock dividend requirements:
     Interest expense -- net                                  $  171,739      $  201,073
     Capitalized interest                                          3,600          55,662
     Rental expense representative of interest factor             46,256          60,210
                                                              ----------      ----------
        Total fixed charges                                      221,595         316,945

     Preferred stock dividends and amortization of
         preferred stock issuance costs                            5,473           8,765
                                                              ----------      ----------
     Combined fixed charges and preferred stock dividend
         requirements                                         $  227,068      $  325,710
                                                              ==========      ==========

Ratio of earnings to fixed charges                                    (a)             (a)
                                                              ==========      ==========

Ratio of earnings to combined fixed charges and
   preferred stock dividend requirements                              (b)             (b)
                                                              ==========      ==========
</Table>

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(a)      Earnings were inadequate to cover fixed charges by $585,993,000 and
         $555,211,000 for the six months ended June 30, 2002 and 2001,
         respectively.

(b)      Earnings were inadequate to cover combined fixed charges and preferred
         stock dividend requirements by $591,466,000 and $563,976,000 for the
         six months ended June 30, 2002 and 2001, respectively.