Child Support Calculator
Estimates monthly child support obligations from both parents' incomes and the number of children using a simplified income-shares model. 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: May 2026
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About this calculator
This calculator uses an income-shares-inspired formula to estimate monthly child support. The formula is: support = max(0, (payerIncome × 0.20 × numChildren) − (receiverIncome × 0.05 × numChildren)). Variables are payerIncome (the non-custodial or higher-earning parent's gross monthly income), receiverIncome (the custodial or lower-earning parent's gross monthly income), and numChildren (the count of dependent minors covered by the order). The payer contributes 20% of monthly income per child group while the receiver's income offsets the obligation by 5% per child group; the max(0, …) floor prevents a mathematically negative result when the receiver out-earns the payer. The formula intentionally smooths over many real-world variables: it ignores parenting-time percentage, healthcare and childcare add-ons, daycare costs, prior-order obligations, and tax filing status. State guidelines almost always factor in those items and can vary the income-share percentage with combined income brackets. Treat the output as a ballpark only; a state-specific guideline worksheet or family-law attorney is required for an enforceable number.
How to use
Example 1: Payer earns $5,000/month, receiver earns $2,000/month, two children. Step 1 — payer contribution: $5,000 × 0.20 × 2 = $2,000. Step 2 — receiver offset: $2,000 × 0.05 × 2 = $200. Step 3 — support: max(0, $2,000 − $200) = $1,800/month. Verify: roughly 36% of payer's gross goes to support, consistent with typical two-child guideline ratios. Example 2: Both parents earn $4,000/month, one child. Step 1 — payer contribution: $4,000 × 0.20 × 1 = $800. Step 2 — receiver offset: $4,000 × 0.05 × 1 = $200. Step 3 — support: max(0, $800 − $200) = $600/month. Verify: when incomes match, the receiver's offset moderates the obligation, recognizing shared financial responsibility.
Frequently asked questions
How is monthly child support calculated using income from both parents?
This calculator combines both parents' incomes rather than looking only at the payer. The payer's income drives the base obligation at 20% per child group, while the receiver's income reduces it at 5% per child group. This reflects the principle that both parents share financial responsibility for the child. The result is floored at zero to prevent negative support, which would be legally meaningless. Most U.S. states use a similar 'income shares' or 'percentage of income' framework, but with their own coefficients and brackets.
Why does the receiving parent's income affect the child support amount?
Courts recognize that both parents have a duty to support their children financially. When the receiving parent earns more, their household contribution reduces the gap the payer must fill. In this formula, each dollar the receiver earns reduces the support obligation by $0.05 per child. This prevents the receiving parent from facing a financial disincentive to earn income. It also reflects modern dual-income family economics, where both parents typically contribute to child-rearing costs.
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 this simplified 20/5 formula without checking your state's actual 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.