Child support in the United States is the court-ordered financial contribution a non-custodial parent makes toward the costs of raising a child after divorce, separation, or paternity proceedings. Every state sets its own guideline formula, but the underlying goal is the same: to keep children at the same standard of living they would have enjoyed if the household had stayed intact.
Our child support estimator uses an income-shares model, the same approach adopted by 41 states and the District of Columbia. It combines both parents' incomes, applies a statutory percentage that scales with the number of children, and adjusts for how much time the paying parent spends with them (parenting time offset). The result is an educated approximation of what a family court is likely to order at the first hearing.
Because state guidelines vary — Massachusetts, Texas, and California each apply distinctly different formulas — this calculator is a starting point, not a substitute for the official worksheet your state provides. Use it to prepare for a mediation session, verify a proposed settlement, or estimate what a modification might look like after a job change.
When to use this tool
- ▸Preparing for a divorce mediation and needing a ballpark figure before hiring a family law attorney.
- ▸Reviewing a proposed marital settlement agreement (MSA) to check if the child support column looks reasonable.
- ▸Filing a modification request after a significant change in circumstances (job loss, relocation, new custody schedule).
- ▸Estimating support for an unmarried co-parent following a paternity establishment.
- ▸Cross-checking an existing court order against current guideline percentages.
Methodology & legal basis
The federal framework for state guidelines is set out in 45 CFR § 302.56, which requires every IV-D state agency to publish a rebuttable-presumption formula. Most states apply an income-shares model: the combined monthly net income of both parents is multiplied by a statutory percentage — 17% for one child, 25% for two, 29% for three — and prorated between the parents.
Our calculator uses income-shares with a New York-style CSSA percentage table as the baseline, then applies a parenting-time offset when the paying parent has the children more than 20% of overnights. Health insurance premiums, child-care costs, and extraordinary medical expenses (add-ons) are not included in the base estimate; courts add these on top of the guideline amount.
Courts may deviate from the guideline number if applying it would be unjust or inappropriate — for example, extraordinarily high combined income, special-needs children, or a shared-custody schedule closer to 50/50. Deviations must be justified on the record.
Key legal terms
- Custodial parent
- The parent with whom the child primarily resides; usually the recipient of support payments.
- Income shares
- A guideline model that presumes children should receive the same proportion of parental income they would have received if the household were intact.
- Imputed income
- Earning capacity a court assigns to an unemployed or underemployed parent when the court finds the parent is voluntarily earning below their potential.
- Deviation
- A court-ordered departure from the presumed guideline amount, permitted only for statutorily recognized reasons.
- Arrears
- Past-due, unpaid child support that continues to accrue interest at the state statutory rate.
Frequently asked questions
Is this calculator legally binding?
No. Only a state family court can enter an enforceable child support order. This tool is an informational estimate to help you prepare.
Which state's formula does it use?
The default is an income-shares model similar to New York's CSSA. Because 41 states use income-shares, the figure is a reasonable proxy — but your state's actual worksheet (available on your Office of Child Support Services website) is authoritative.
Does it account for shared 50/50 custody?
Partially. The custody-percentage input applies a parenting-time offset above 20% overnights, but true 50/50 arrangements are typically negotiated separately and may reduce the transfer amount substantially.
How often can I modify child support?
Most states allow a modification when there is a substantial change in circumstances, generally defined as a 10–20% change in income or a major change in the parenting schedule. Some states allow a review every three years regardless.
What happens if the paying parent stops paying?
Arrears accrue with statutory interest, and enforcement remedies include wage garnishment, tax refund interception, license suspension, and, in extreme cases, contempt of court.
Is child support tax-deductible for the payer?
No. Since 2019 neither child support nor alimony is deductible by the payer or taxable to the recipient at the federal level.
This estimator is intended for informational purposes and does not replace advice from a licensed family law attorney in your state. Before signing any child support stipulation or responding to a filed petition, review the numbers against your state's official worksheet and consult counsel.