The statutory amount required for two children is 25%, but only up to the combined incomes of both parents of $80,000; after that, it is up to the courts to decide. The exact calculation is complex and not for this message. You are allowed to agree between you to deviate from this statutory amount, and you should be insisting that you cannot afford such a big chunk of your paycheck and will be forced to default on such an intolerable obligation. I strongly suggest you try mediation to resolve this and any other matters you both have outstanding.
If you are located in the NYC metro area, call me at 212-370-1660 to discuss further.
Leonard M. Weiner, Esq. /Divorce Solutions