<PAGE>   1
                                                                      Exhibit 99

                            TRW Inc. and Subsidiaries
                        Computation of Ratio of Earnings
                          to Fixed Charges - Unaudited

                         (In millions except ratio data)

<TABLE>
<CAPTION>


                                                              Years Ended December 31
                             Six Months Ended -------------------------------------------------------------
                              June 30, 1999      1998        1997           1996        1995       1994
                             ---------------- ---------- -------------- ------------- --------- -----------

<S>                           <C>           <C>         <C>            <C>            <C>        <C>
Earnings from continuing
  operations before income
  taxes                        $  224.5(A)    $  746.1    $  239.7(B)    $  302.2(C)   $  625.5   $  435.5

Unconsolidated affiliates         (30.9)           1.0        (8.0)           1.4           1.3       (0.6)

Minority earnings                   9.2           10.5        20.2           11.5          10.8        7.7

Fixed charges excluding
  capitalized interest            214.7          174.3       123.9          129.0         137.2      145.3
                               --------       --------    --------       --------      --------   --------

Earnings                       $  417.5       $  931.9    $  375.8       $  444.1      $  774.8   $  587.9
                               --------       --------    --------       --------      --------   --------



Fixed Charges:
Interest expense               $  184.7       $  114.4    $   75.4       $   84.2      $   94.7   $  104.7

Capitalized interest                1.7            4.7         4.5            3.5           5.1        6.6

Portion of rents representa-
  tive of interest factor          30.0           59.9        48.5           43.2          41.4       39.2

Interest expense of uncon-
  solidated affiliates              0.0            0.0         0.0            1.6           1.1        1.4
                               --------       --------    --------       --------      --------   --------

Total fixed charges            $  216.4       $  179.0    $  128.4       $  132.5      $  142.3   $  151.9
                               --------       --------    --------       --------      --------   --------

Ratio of earnings to fixed
  charges                           1.9x           5.2x        2.9x           3.4x          5.4x      3.9x
                               --------       --------    --------       --------      --------   --------
</TABLE>

(A)    Earnings from continuing operations before income taxes for the six
       months ended June 30, 1999 of $224.5 million, includes an $85.3 million
       earnings charge for purchased in-process research and development. See
       "Acquisitions" footnote in the Notes to Financial Statements.

(B)    The 1997 earnings from continuing operations before income taxes of
       $239.7 million includes a $548 million earnings charge for purchased
       in-process research and development. See "Acquisitions" footnote in the
       Notes to Financial Statements of the Company's 1997 Annual Report to
       Shareholders.

(C)    The 1996 earnings from continuing operations before income taxes of
       $302.2 million includes a charge of $384.8 million as a result of actions
       taken in the automotive and space and defense businesses. See "Special
       Charges and Divestiture" footnote in the Notes to Financial Statements of
       the Company's 1996 Annual Report to Shareholders.