<PAGE>   1
<TABLE>
<CAPTION>
<S>                                                 <C>                      <C>
            NUMBER                                                                           SHARES

    SA
                                                     SIMPLEX

INCORPORATED UNDER THE LAWS OF                                                SEE REVERSE FOR STATEMENTS RELATING
    THE STATE OF DELAWARE                                                            TO RIGHTS, REFERENCES,
                                                                              PRIVILEGES AND RESTRICTIONS, IF ANY


This Certifies that                                                                             CUSIP 828854 10 9



is the owner of

               FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK, PAR VALUE $0.001 PER SHARE, OF
                                             SIMPLEX SOLUTIONS, INC.

      transferable only on the books of the Corporation by the holder hereof in person or by duly
      authorized Attorney upon surrender of this certificate properly endorsed. This certificate is not
      valid until countersigned and registered by the Transfer Agent and Registrar.

            WITNESS the facsimile seal of the Corporation and the facsimile signatures of its duly
      authorized officers.

      Dated

            [SIGNATURE ILLEGIBLE]                                                  [SIGNATURE ILLEGIBLE]
                                                      [SEAL]
      CHAIRMAN AND CHIEF EXECUTIVE OFFICER                                                SECRETARY
</TABLE>

COUNTERSIGNED AND REGISTERED:
    LASALLE BANK NATIONAL ASSOCIATION
                       TRANSFER AGENT
                        AND REGISTRAR

BY
<PAGE>   2

                            SIMPLEX SOLUTIONS, INC.

        A statement of the powers, designations, preferences and relative,
participating, optional or other special rights of each class of stock or
series thereof and the qualifications, limitations or restrictions of such
preferences and/or rights as established, from time to time, by the Certificate
of Incorporation of the Corporation and by any certificate of determination,
the number of shares constituting each class and series, and the designations
thereof, may be obtained by the holder hereof upon request and without charge
at the principal office of the Corporation.

        The following abbreviations, when used in the inscription on the face
of this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

<TABLE>
        <S>                                            <C>
        TEN COM   --  as tenants in common              UNIF GIFT MIN ACT -- ...................Custodian...............
        TEN ENT   --  as tenants by the entireties                                 (Cust)                    (Minor)
        JT TEN    --  as joint tenants with right of                         under Uniform Gifts to Minors
                      survivorship and not as tenants                        Act........................................
                      in common                                                                 (State)
                                                        UNIF TRF MIN ACT  -- .............Custodian (until age.........)
                                                                                 (Cust)
                                                                             ....................under Uniform Transfers
                                                                                    (Minor)
                                                                             to Minors Act..............................
                                                                                                   (State)
</TABLE>

    Additional abbreviations may also be used though not in the above list.


        FOR VALUE RECEIVED,___________________________hereby sell, assign and
transfer unto

PLEASE INSERT SOCIAL SECURITY OR OTHER
   IDENTIFYING NUMBER OF ASSIGNEE
--------------------------------------

--------------------------------------


_______________________________________________________________________________
 (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

_______________________________________________________________________________

_______________________________________________________________________________

________________________________________________________________________ Shares
of the capital stock represented by the within Certificate, and do hereby
irrevocably constitute and appoint

______________________________________________________________________ Attorney
to transfer the said stock on the books of the within named Corporation
with full power of substitution in the premises.

Dated________________________


                                X_______________________________________________

                                X_______________________________________________
                                 THE SIGNATURE(S) TO THIS ASSIGNMENT MUST
                                 CORRESPOND WITH THE NAME(S) AS WRITTEN UPON THE
                       NOTICE:   FACE OF THE CERTIFICATE IN EVERY PARTICULAR,
                                 WITHOUT ALTERATION OR ENLARGEMENT OR ANY
                                 CHANGE WHATEVER.

Signature(s) Guaranteed




By___________________________________
THE SIGNATURE(S) SHOULD BE GUARANTEED
BY AN ELIGIBLE GUARANTOR INSTITUTION
(BANKS, STOCKBROKERS, SAVINGS AND
LOAN ASSOCIATIONS AND CREDIT UNIONS
WITH MEMBERSHIP IN AN APPROVED
SIGNATURE GUARANTEE MEDALLION PROGRAM),
PURSUANT TO S.E.C. RULE 17Ad-15.