Generally speaking, child support is determined by the courts through the use of a child support model (with calculations) that are adopted by the state.  The court determines the amount by plugging in income in to a formula and allowing some deductions but not many.  The parties can agree on the amount of child support but it can never be below the percetage allocated to each spouse.  The custodial parent generally receives more support but each state deals with that issue based on various other factors in the custody agreement.  You need to sit down with an attorney on this issue or just go to the court and ask for the guidelines and support worksheet.  They have them there.  Good luck.