The size of your child support payment depends heavily on where you live. States generally use one of three models to determine the base child support amount due.Explanations of each model and the states that use them follow. Welcome to the Pennsylvania Child Support Estimator. This tool can be used to estimate the amount of your monthly child support amount. To calculate child support, Pennsylvania uses a method referred to as the income shares model to determine child support payments. In any state, get an idea of how much child support you might pay or have to receive after your divorce. The Pennsylvania Child Support Website is an easy way to access child support program information and case details. Every state has its own child support laws and guidelines, so they will vary from state to state. The guideline formula presumes the parent paying support has between 30 and 40 percent of annual overnights in the custody schedule.