How Child Support Is Calculated
Child support calculations vary by state, but most US states use one of two primary models: the income-shares model or the percentage-of-income model. The income-shares model, used by about 40 states, aims to provide children with the same proportion of parental income they would have received if the family had remained intact. This calculator uses a simplified income-shares approach to generate an estimate.
In the income-shares model, both parents' incomes are combined to determine the total child-rearing cost using state-published schedules. Each parent's share of that obligation is proportional to their share of combined income. The non-custodial parent pays their share to the custodial parent, while the custodial parent's share is presumed spent directly on the child.
The Income-Shares Formula
The basic calculation works as follows: (1) Combine both parents' gross monthly incomes. (2) Look up the basic child support obligation from the state schedule based on combined income and number of children. (3) Determine each parent's income percentage share. (4) Multiply the basic obligation by the non-custodial parent's income share. (5) Adjust for custody time — if the non-custodial parent has the child more than a threshold percentage (often 35–40%), the obligation is reduced.
This calculator uses approximate obligation rates based on typical state schedules: roughly 17% of combined income for one child, 25% for two, 29% for three, 31% for four, and 35% for five or more children — then applies each parent's proportional share and a custody time adjustment.
What Courts Actually Consider
Real child support orders involve many factors beyond the basic formula. Courts may deviate from guideline amounts based on: extraordinary medical expenses for the child; special educational needs; childcare costs required for a parent to work; health insurance premiums; travel costs for visitation across long distances; prior support orders for other children; and the standard of living the child would have enjoyed had the family stayed together. Either parent can request a deviation by demonstrating that the guideline amount would be unjust given specific circumstances.
Custody and Its Impact on Support
Custody percentage significantly affects child support. In sole or primary custody arrangements (one parent has the child most of the time), support flows straightforwardly from non-custodial to custodial parent. In shared or joint custody situations — where the non-custodial parent has the child for 35% or more of overnights — most states apply an offset calculation that reduces the guideline amount, since both parents are bearing direct child-rearing costs. Some states use a full offset model where each parent's obligation to the other is calculated and only the net difference is paid.
Modifying Child Support
Child support orders can be modified when there is a substantial change in circumstances: a significant income change (typically 10–15% or more), a change in custody arrangement, major changes in the child's needs, or a parent becoming disabled or unemployed. Most states allow modification reviews every 3 years automatically. Failing to pay child support as ordered can result in wage garnishment, tax refund intercepts, license suspension, and in extreme cases, contempt of court charges.
Planning Your Finances Around Child Support
Whether paying or receiving child support, build it into your monthly budget as a fixed expense. If you're the paying parent, remember that child support is not tax-deductible (unlike alimony under pre-2019 divorce agreements). If you're the receiving parent, child support is not taxable income. Consider setting up automatic bank transfers to ensure timely payment and avoid enforcement actions. Keep records of all payments made and received in case of future disputes.