Child Support Calculator
Estimates monthly child support from both parents' incomes and the number of children using New York's Child Support Standards Act (CSSA) percentage-of-income guideline. Use it for early divorce planning, mediation prep, or sanity-checking a state guideline calculator — not as a substitute for a court order.
Last updated: September 2026
Formula below · 3 sources (acf.hhs.gov, omnicalculator.com, Wikipedia) · Updated Sep 2026
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About this calculator
This calculator applies the New York Child Support Standards Act (CSSA, Domestic Relations Law § 240(1-b)), one of the main U.S. guideline models. Step 1: each parent's income is reduced by FICA (7.65%), as the CSSA deducts Social Security and Medicare taxes from gross income. Step 2: the two incomes are added to get combined parental income. Step 3: the child support percentage for the number of children is applied: 17% for one child, 25% for two, 29% for three, 31% for four and 35% for five or more. The percentages apply automatically to combined income up to $193,000 a year (the cap in effect from March 1, 2026); above that the court decides whether to apply them, so this estimate stops at the cap. Step 4: the non-custodial (paying) parent owes his or her pro-rata share: support = min(combined, cap) × percentage × payer income / combined income. Below the cap this equals the payer's income after FICA × the percentage, so the receiver's income only matters for high combined incomes. Variables: payer and receiver gross monthly income and number of children. Not included: add-ons for child care, health insurance and unreimbursed medical costs (shared in proportion to income), local income taxes deducted in New York City and Yonkers, shared-custody adjustments, the self-support reserve for low-income payers, and the different tables used by income-shares states. Treat the result as an estimate; your state's official worksheet decides the legal amount.
How to use
Example 1: Payer earns $5,000/month, receiver earns $3,000/month, two children. Step 1 — incomes after FICA: $5,000 × 0.9235 = $4,617.50 and $3,000 × 0.9235 = $2,770.50; combined $7,388. Step 2 — combined obligation: $7,388 × 25% = $1,847. Step 3 — payer's share: $4,617.50 / $7,388 = 62.5%, so support = $1,847 × 0.625 ≈ $1,154.38/month (the same as $4,617.50 × 25%). Example 2: Both parents earn $4,000/month, one child. Payer after FICA: $3,694; support = $3,694 × 17% = $627.98/month. Example 3 (above the cap): payer $20,000/month, receiver $5,000/month, one child. Combined after FICA = $23,087.50, above the $16,083.33 monthly cap; support = $16,083.33 × 17% × 0.8 = $2,187.33/month, before any discretionary amount on income above the cap.
Frequently asked questions
How is monthly child support calculated using income from both parents?
Under the CSSA model used here, both parents' incomes (less FICA) are added and the guideline percentage for the number of children (17%, 25%, 29%, 31% or 35%) is applied to combined income up to the $193,000 cap. The non-custodial parent pays his or her share of that obligation in proportion to income, and the custodial parent's share is presumed to be spent directly on the children. Most other states use an 'income shares' table instead, but the results are usually of a similar size; check your state's official calculator for the legal amount.
Why does the receiving parent's income affect the child support amount?
In a combined-income model such as the CSSA, the custodial parent's income raises the combined obligation but also lowers the payer's percentage share of it, and the two effects cancel out below the income cap. So for most families the receiver's income does not change the payer's guideline amount; it matters when combined income exceeds the cap, and in add-ons such as child care and health insurance, which are split in proportion to income. In income-shares states, the receiver's income can change the amount more, because the table percentages fall as combined income rises.
What are common mistakes when estimating child support with this calculator?
Entering net (after-tax) income instead of gross income produces a low estimate, since most state guidelines use gross income before adjustments. Forgetting to add bonuses, commissions, and self-employment income understates the payer's true earning capacity. Mixing weekly or biweekly pay with the monthly formula by a factor of 4 instead of 4.33 introduces ~8% errors. Treating equal-parenting-time custody as no obligation is wrong — most jurisdictions still require some support from the higher earner. Finally, applying New York's CSSA percentages without checking your own state's guideline can produce results that differ from the legally enforceable amount by hundreds of dollars per month.
When should I NOT rely on this child support calculator?
Never use a generic calculator to set or modify a legal child support order — only a court order is enforceable. The output is not legal advice and ignores state-specific guidelines that may include healthcare premiums, childcare costs, education expenses, and parenting-time adjustments. High-income cases (combined gross income above guideline caps) require judicial discretion, not formula. Cross-state moves trigger Uniform Interstate Family Support Act analysis that this tool cannot perform. If you are a self-employed parent, have variable income, or share custody more than 30%, the formula's assumptions break down — consult a family-law attorney.
How can I get a more accurate child support estimate for my state?
Every state publishes an official guideline worksheet — search '[state] child support guideline calculator' to find the version maintained by the state's child support enforcement agency or judicial council. These worksheets ask for healthcare costs, childcare costs, prior-order obligations, parenting-time percentages, and tax filing status. Some states (California, Florida, New York, Texas) have especially detailed calculators online. For contested or high-stakes cases, retain a family-law attorney who can apply local case law and judicial discretion. Mediators and court self-help centers can also help non-attorneys complete the worksheets correctly.