Child Support Calculator

Q: How is child support calculated in most states?

Most states (about 40) use the income shares model, which estimates what parents would have spent on their children in an intact household and divides that amount based on each parent's share of combined income. A few states use the percentage-of-income model (based only on the non-custodial parent's income). The specific percentages, deductions, and adjustments vary by state.

Q: When can I request a child support modification?

You can request a modification when there is a material change in circumstances. Most states define this as a 15-20% change in either parent's income, a significant change in custody arrangements, or a change in the children's needs. Many states also allow automatic review every 3 years. The modification takes effect from the date of filing, not retroactively.

Q: How does joint custody affect child support?

Joint (shared) custody typically reduces the child support obligation by 10-30%, depending on the state and the exact split of overnights. Both parents are directly paying for the child's expenses during their parenting time. A 50/50 split does not mean zero support — if there's an income disparity, the higher earner still pays a reduced amount.

Q: What happens if child support isn't paid?

Unpaid child support (arrears) accrues as a legal debt and cannot be discharged in bankruptcy. Enforcement actions include wage garnishment (up to 50-65% of disposable income), tax refund interception, license suspension, passport denial (for arrears over $2,500), and contempt of court charges. If you cannot pay, file for modification immediately.

Estimate child support obligations using the income shares model. See how payments affect your monthly budget, compare state guidelines, and check whether you qualify for a modification.

Estimate child support using the income shares model

Parent 1 gross annual income

Non-custodial parent (higher earner typically)

Parent 2 gross annual income

Custodial parent

Number of children

Children covered by this order (1-6)

Custody arrangement

Joint custody typically reduces obligation 10-30%

State

Each state has different guideline formulas

Annual healthcare costs (children)

Insurance premiums + out-of-pocket for children

Annual childcare costs

Daycare, after-school, summer camp

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How to Use This Calculator

Basic Support Estimate tab

The default tab. Enter both parents' gross annual incomes, number of children, custody arrangement (sole, joint, or split), and state. The calculator uses the income shares model to compute each parent's proportional share of the child support obligation. Expand "More options" to add healthcare and childcare costs, which are split pro-rata between parents on top of the base support amount.

Budget Impact tab

See how child support payments affect your monthly finances. Enter whether you are the paying or receiving parent, the monthly support amount, your gross income, and filing status. The calculator shows your post-support take-home pay, what percentage of your income goes to support, how it compares to typical guidelines (15–30% of gross), and whether you remain above the self-support reserve.

Modification Check tab

Determine if you may qualify to modify an existing child support order. Enter your current support order, income at the time of the order, current income, and years since the order. The calculator checks whether the income change meets the typical 15–20% material change threshold, estimates what a new order might be, and evaluates additional factors like custody changes and children’s needs.

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The Formula

Most US states use the income shares model, which estimates the amount parents would spend on their children if the household were intact, then divides that obligation proportionally based on each parent’s income:

Combined Gross Income = Parent 1 Income + Parent 2 Income

Each Parent's Share = Their Income / Combined Income

Base Support Obligation = Combined Income × Guideline % (varies by # of children)
• 1 child: 17–20% • 2 children: 25–28% • 3 children: 29–33%
• 4 children: 31–35% • 5+ children: 34–38%

Adjusted Obligation = (Base + Healthcare + Childcare) × Custody Factor
• Sole custody: 100% • Joint: ~75% • Split: ~60%

Non-Custodial Parent Pays = Adjusted Obligation × Their Share %

The non-custodial parent (or higher earner in joint custody) pays their proportional share of the total obligation. Healthcare premiums and work-related childcare costs for the children are added to the base amount and split proportionally. Joint and split custody arrangements reduce the obligation because both parents are directly covering costs during their parenting time.

Actual state calculations are more complex — they use lookup tables, deviation factors, and judicial discretion. This calculator provides a reasonable estimate for planning purposes.

Example

Maria and James — divorced parents in Texas, 2 children

Maria earns $80,000/year and James earns $50,000/year. They have two children ages 7 and 10. Maria has sole custody. Annual healthcare costs for the children are $2,400 and childcare costs are $4,800.

Basic Support Estimate tab

Combined gross income$130,000/yr

Maria's share61.5%

James's share38.5%

Base support (26.5% of combined)$34,450/yr

With healthcare + childcare add-ons$41,650/yr

Maria's obligation (sole custody, 61.5%)$2,135/mo

Since Maria is the custodial parent, James (non-custodial, 38.5% share) would pay approximately $1,336/mo in child support. Maria’s larger share is fulfilled through direct care of the children.

Budget Impact tab

James's gross monthly income$4,167/mo

After taxes (single, TX 0%)$3,484/mo

After support payment$2,148/mo

Support as % of gross32.1%

James’s support obligation is 32.1% of gross income, slightly above the typical guideline range. If James’s income changes significantly, he could file for modification.

FAQ

How is child support calculated in most states? ▼

Most states (about 40) use the income shares model, which estimates what parents would have spent on their children in an intact household and divides that amount based on each parent’s share of combined income. A few states use the percentage-of-income model (based only on the non-custodial parent’s income), and some use the Melson formula (a more complex variation). The specific percentages, deductions, and adjustments vary by state.

Is child support taxable or tax-deductible? ▼

No. Under current federal tax law (made permanent by OBBBA/TCJA), child support is neither taxable to the recipient nor deductible by the payer. This is different from alimony, which under pre-2019 agreements may still be deductible/taxable. Child support has no impact on either parent’s federal tax return.

When can I request a child support modification? ▼

You can request a modification when there is a material change in circumstances. Most states define this as a 15–20% change in either parent’s income, a significant change in custody arrangements, or a change in the children’s needs (such as new medical expenses). Many states also allow automatic review every 3 years. The modification takes effect from the date of filing, not retroactively — so if your income drops, file promptly.

How does joint custody affect child support? ▼

Joint (shared) custody typically reduces the child support obligation by 10–30%, depending on the state and the exact split of overnights. The logic is that both parents are directly paying for the child’s expenses during their parenting time. Most states use a formula that adjusts the obligation based on the percentage of overnights each parent has. A 50/50 split does not mean zero support — if there’s an income disparity, the higher earner still pays a reduced amount.

What happens if child support isn't paid? ▼

Unpaid child support (arrears) accrues as a legal debt and cannot be discharged in bankruptcy. Enforcement actions include wage garnishment (up to 50–65% of disposable income), tax refund interception, suspension of driver’s and professional licenses, passport denial (for arrears over $2,500), and in extreme cases, contempt of court charges. Interest accrues on unpaid amounts in most states. If you cannot pay, file for modification immediately rather than simply not paying.

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