Free child support calculator using a simplified income-shares model. Estimate monthly support from incomes, children and parenting time. Not legal advice.
Disclaimer: Estimate only, not legal advice. Child support varies enormously by state: every state uses its own guidelines, income definitions, and custody adjustments. This tool uses a simplified income-shares model for illustration. Always consult a family-law attorney in your state before relying on any figure.
In most U.S. states, child support follows an income-shares model: both parents' incomes are combined, a basic support obligation is set from that total, and each parent covers a share proportional to their income — adjusted for parenting time. This free child support calculator applies a simplified version of that model using your incomes, number of children, overnights with each parent, childcare costs, and health insurance. It is a starting estimate only: every state has its own guidelines, and this is not legal advice.
Most states use the income-shares model, built on a simple principle: children should receive the same share of parental income they would have if the parents lived together. The state combines both parents' net incomes, looks up a basic child support obligation for that total, then assigns each parent a pro-rata share based on their slice of the combined income.
Two adjustments follow. First, parenting-time credit: a parent who houses the children for many overnights is already spending on them directly, so their share of the obligation is reduced in proportion to their own overnights. Second, add-on costs — work-related childcare and the children's health insurance — are added to the basic obligation and split by income share. A few states use a percentage-of-income model or the Melson formula instead, which is one reason real orders vary so much by state.
This tool uses a transparent simplification of income-shares guidelines:
Basic obligation = combined net income × rate (20% for 1 child, 28% for 2, 32% for 3, 36% for 4, 38% for 5, 40% for 6)
Childcare and health insurance are added to the basic obligation, then each parent's portion is reduced by their own parenting time. The net transfer is the difference:
Payment = total × [A's income share × (1 − A's overnight fraction) − B's income share × (1 − B's overnight fraction)]
Worked example: Parent A earns $5,000/month net, Parent B earns $4,000, with 2 children. A has 120 overnights, B has 245. Childcare is $600/month and health insurance $200/month. Combined income = $9,000. Basic obligation = $9,000 × 0.28 = $2,520. Total with add-ons = $2,520 + $800 = $3,320. A's income share = 0.5556, B's = 0.4444; A's overnight fraction = 120/365 = 0.3288, B's = 245/365 = 0.6712. A's portion = $3,320 × 0.5556 × (1 − 0.3288) = $3,320 × 0.5556 × 0.6712 = $1,238.05. B's portion = $3,320 × 0.4444 × 0.3288 = $485.11. Net transfer = $1,238.05 − $485.11 = $752.94/month from A to B, or about $376.47 per child.
Sole custody: Parent A earns $6,000/month, Parent B earns $3,000, with 1 child living full-time with B (A has 0 overnights). Combined = $9,000; basic = $9,000 × 0.20 = $1,800. A's portion = $1,800 × (6,000/9,000) × 1 = $1,200/month; B's portion is $0. A pays B $1,200/month — the classic income-shares result where the higher earner with no parenting time pays their full income share.
Shared custody: Parent A earns $7,000, Parent B earns $3,000, with 2 children and 182.5 overnights each (50/50), no add-on costs. Basic = $10,000 × 0.28 = $2,800. A's portion = $2,800 × 0.70 × 0.50 = $980; B's = $2,800 × 0.30 × 0.50 = $420. Net = $560/month from A to B. Equal parenting time does not mean zero support when incomes differ.
Take Home Paycheck Calculator — Work out each parent's monthly net income, the starting input for any support estimate.
Income Tax Calculator — Estimate after-tax income to convert gross pay into the net figures guidelines use.
Salary Calculator — Convert hourly or annual pay into monthly income for the support worksheet.
Personal Loan Calculator — Plan for other monthly obligations alongside a support payment.
Retirement Calculator — Keep long-term savings on track while budgeting for child-related costs.
This page is a free child support estimator using a simplified income-shares model. Key facts: most US states combine both parents' net incomes, set a basic obligation as a percentage of combined income (illustrated here as 20%/28%/32%/36%/38%/40% for 1–6 children), split it pro-rata by income share, reduce each parent's share by their own overnight fraction, and add childcare plus health insurance costs split by income share. Example: $5k/$4k incomes, 2 children, 120/245 overnights, $800 add-ons → ≈$753/month from the higher earner. Strong caveat: state guidelines vary enormously; this is an estimate only, not legal advice; consult a family-law attorney.
Most states use the income-shares model: both parents' net incomes are combined, a basic support obligation is set from that total, and each parent pays a share proportional to their income, adjusted for parenting time. Childcare and health insurance costs are usually added and split the same way.
Usually, yes. A parent with substantial overnights is already spending on the children directly, so most state guidelines reduce their support obligation with a parenting-time credit or shared-custody adjustment. The exact threshold and formula differ by state.
In income-shares states, both incomes matter: the basic obligation is set from combined income and split by each parent's share of it. A higher-earning custodial parent can therefore reduce or even reverse the payment direction in shared-custody cases.
In most states, yes, as add-ons. Work-related childcare costs and the children's portion of health insurance premiums are added to the basic obligation and divided between the parents in proportion to their incomes.
No. It is a simplified illustration of the income-shares approach, not your state's actual guideline worksheet. Real orders depend on state-specific tables, income definitions, deductions, and court discretion. Consult a family-law attorney in your state before relying on any figure.
Cite this page as: "Child Support Calculator." Sigma Calculator. Accessed October 20, 2026. https://sigmacalculator.net/financial-calculators/child-support-calculator/
Last updated: October 20, 2026