Free Child Support Calculator
Enter each parent's monthly income, the number of children, and how many overnights per year the children spend with each parent. The calculator estimates monthly support using a simplified income-shares model like the one most states use.
This free child support calculator estimates support with the income-shares approach used by most states: it combines both parents' incomes, applies a percentage based on the number of children, splits the obligation by income share, and credits parenting time. For example, with $5,000 and $3,000 monthly incomes, two children, and 100 overnights with Parent 1, estimated support is about $1,045 a month paid by Parent 1. Every state has its own official guidelines, so treat this as a starting estimate, not a legal figure.
Estimates only, and a simplification. Every state publishes its own official child support guidelines with specific tables, deductions, and adjustments that this tool does not replicate. This is not legal advice. Consult a family law attorney for your situation.
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How child support math works
Most states use the income-shares model. The idea is that children should receive the same share of combined parental income they would have received if the parents lived together. So the calculation starts by adding both parents' monthly incomes, then applies a percentage that rises with the number of children.
The percentages in this calculator are simplified planning figures: about 20 percent of combined income for one child, 25 percent for two, 29 percent for three, and 32 percent for four or more. Real state guidelines use detailed tables that also account for the income level itself, because higher-income families spend a smaller share on children.
That total obligation is then split between the parents in proportion to income. If one parent earns $5,000 and the other $3,000, the combined income is $8,000 and the first parent's share of any obligation is five-eighths. The split reflects ability to pay, not custody.
Parenting time then adjusts the transfer. The parent with fewer overnights is the presumed payer, and their payment is reduced by a credit reflecting the costs the other parent bears during their time. More overnights with the payer means a lower payment, which is why custody schedules and support amounts are negotiated together.
Real guidelines add layers this tool skips: health insurance premiums, childcare costs, extraordinary medical expenses, and deductions for other children. Some states use a percentage-of-income model instead of income shares, and a few use the older Melson formula. Always run your facts through your state's official calculator before relying on any number.
Child support questions
How is child support calculated?
Most states use the income-shares model: combine both parents' monthly incomes, look up the basic obligation for that income and child count in the state table, divide it between parents by income percentage, then adjust for parenting time, health insurance, and work-related childcare. A few states use a flat percentage of the noncustodial parent's income instead.
Does more custody time lower child support?
Usually. Most state formulas reduce support as the payer's overnights increase, with the credit growing once time passes a threshold, commonly 90 to 128 nights a year. Near-equal parenting time can reduce support dramatically, though rarely to zero when incomes differ, because the higher earner still owes a transfer.
What income counts for child support?
States count nearly everything: wages, salaries, commissions, bonuses, tips, self-employment income, rental income, investment returns, and sometimes benefits. Courts can also impute income to a parent who is voluntarily unemployed or underemployed, basing support on earning capacity rather than actual earnings.
Can child support be modified later?
Yes. Courts modify support when circumstances change substantially: typically a 15 to 20 percent income change, job loss, disability, a new custody arrangement, or a child's changing needs. Many states also allow periodic reviews every few years. File promptly, because modifications usually apply from the filing date, not retroactively.