This is a toughie, and a problem I am currently dealing with too. In many states a spouse who is college educated, but chooses not to work can have income "imputed" to them. In other words the court will figure out what they are capable of earning and figure child support based on that amount. Sounds good, but enforcement is difficult. First they have to go into arrears, then hauled into court for a hearing to determine contempt. And then what. If they don't have it, they don't have it. Some courts will take away driver's licenses and eventually jail time.
Put in a google search: child support calculator (along with your jurisdiction) and you should get several cites that will give you a start to finding the particular calculator your jurisdiction uses. Some state social services departments have online calculators, but not all. The calculators for one state don't work in another, they are not all the same.