Child Support Payment Calculator
This calculator estimates monthly child support obligations using the income shares model, which is used by most US states. The model combines both parents' net monthly incomes to arrive at a basic support obligation, then each parent pays a share proportional to their income. Enter both parents' net incomes, the number of children, and the noncustodial parent's parenting time percentage to get an estimate. All figures are estimates only and do not constitute legal advice. Consult a family law attorney or your state's child support enforcement agency for binding calculations.
Income shares formula
Combined Income = Custodial Net Income + Noncustodial Net Income
Basic Obligation = Combined Income * Guideline Rate (by children count)
NCP Share = Noncustodial Income / Combined Income
Monthly Payment = Basic Obligation * NCP Share * (1 - Parenting Credit)
The guideline rate used here is an approximation based on typical income shares tables: approximately 17% for 1 child, 25% for 2 children, 29% for 3 children, 31% for 4 children, and 32% for 5 or more children. These rates vary by state. A parenting time credit of up to 50% is applied when the noncustodial parent's time exceeds 20%, scaling linearly to 50% at equal parenting time.
How the income shares model works
- Both parents' net incomes are combined to approximate what would have been spent on the children in an intact household.
- State guideline tables convert combined income and number of children into a basic support obligation.
- Each parent's share of the obligation is proportional to their share of combined income.
- The noncustodial parent pays their proportional share to the custodial parent.
- Additional costs such as health insurance premiums and childcare may be added on top of the basic obligation.
Child support calculator: frequently asked questions
How is child support calculated in the US?
Most states use the income shares model, which estimates the amount both parents would have spent on the child if they lived together, then apportions that cost based on each parent's share of combined income. The noncustodial parent pays their proportional share to the custodial parent.
What is the income shares model?
The income shares model combines both parents' net incomes to determine a total child support obligation from state guidelines tables. Each parent's share of that obligation is proportional to their contribution to the combined income.
Does custody percentage affect child support?
Yes. Many states apply a parenting time credit that reduces the noncustodial parent's obligation when they have the child for more than a threshold percentage of nights (commonly 20% to 40%). The more time a parent has, the lower the credit-adjusted obligation.
Are these estimates legally binding?
No. This calculator produces estimates only. Actual child support orders are set by a court or administrative agency using each state's specific guidelines, which may include additional factors such as health insurance costs, childcare, and special needs.
Where can I find official state guidelines?
The Office of Child Support Services (OCSS), part of the U.S. Department of Health and Human Services, maintains links to every state's child support guidelines at acf.hhs.gov. Your state's family court or child support enforcement agency also publishes the current schedule.
Official sources
- U.S. Department of Health and Human Services, Office of Child Support Services: State Income Withholding and Guidelines.
- U.S. DHHS, OCSS: Child Support Services homepage.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.