The person responsible for paying child support is referred to as the "Obligor".
The first step in calculating child support is figuring out the Obligor's "net monthly resources". Net resources is all income from all sources minus the following: return of principal or capital; accounts receivable; benefits paid under the Temporary Assistance for Needy Families program or other federal public assistance programs; payments for care of a foster child; social security taxes; federal income tax assuming one person claiming a personal exemption and standard deduction; union dues; cost of medical insurance or medical support for the child(ren) before the court; and non-discretionary retirement plan contributions if the Obligor doesn't pay social security taxes. Generally, the Obligor's net resources for the past year are calculated and then averaged to a monthly amount.
If the Obligor's net monthly resources are less than $8,550, then the Obligor pays a percentage of his net monthly resources as child support. The amount of the percentage depends on the number of children before the court. For example, if the Obligor has to pay support for one child, then the Obligor's child support amount will be 20% of the Obligor's net monthly resources. It's 25% for two children and 30% for three children.
If the Obligor has to pay support for children in multiple households, then the percentages depend on two factors. First, how many children are before the court? Second, how many children not before the court does the Obligor have to pay support for? For example, if there is one child before the court and the Obligor also has to pay support for another child not before the court, then the Obligor has to pay 17.50% of his net monthly resources for the support of the child before the court. Also by way of example, if there are two children before the court and the Obligor also has to pay support for another child not before the court, then the Obligor has to pay 22.50% of his net monthly resources for the support of the two children before the court.
If the Obligor's net monthly resources are more than $8,550, then the appropriate percentage is applied to the maximum amount of $8,550. If the costs of the child's proven needs are more than the resulting child support based on the maximum amount, the excess costs are divvied among the parties as the court see fit.