State-specific child support calculators are based upon the statutes of that state, but they generally require inputting factors such as each party's income, child-care expenses, extraordinary medical expenses, and the children’s health insurance costs, as noted by Legal Aid Network of Kentucky. Mathematical formulas establish each party's proportionate share of presumptive child support. Some states, such as Indiana, include the number of parenting overnights in determining how much each parent pays.
Child support laws are established by each state and thus differ from state to state, as noted by AllLaw. The Indiana Child Support Rules and Guidelines note that there are at least five different approaches to calculating child support, including the Income Shares approach used by Indiana. A good example of a list of the factors used to determine child support is in the Indiana guidelines, which are available online. As pointed out by the American Bar Association, if one party is not voluntarily not working, a judge may impute income to him or her.
Most state court websites have information about their specific child support calculations, and since the calculators use the formula chosen by each state, it is important to use the correct state calculator. AllLaw.com provides a link to each state calculator. A judge may deviate from the guidelines in each individual case, but as the California Courts website notes, deviation is the exception.