How different custody arrangements change the estimated support payment — all other inputs held constant. Currently selected scenario highlighted.
Payer Nights/Yr
Custody %
Arrangement
Monthly Support
Annual Total
Custody Scenario Chart
Highlighted bar = closest match to your entered custody nights. Adjust the payer nights in the Calculator tab to see the highlighted bar shift.
Income × Custody Sensitivity Matrix Payer income (rows) × nights (cols) → monthly support
Modification Threshold Solver
Courts typically review support orders when income changes by 15–20%. Find the income levels that would trigger a modification request.
Note: Most states apply a custody adjustment when the payer has more than 40% of overnights (146+ nights/year). At 50/50 custody, only the income difference typically drives payment.
Long-Term Payment Planner
Enter each child's current age to model step-down support as children turn 18, and project total lifetime payments.
Child Ages
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Monthly
$0
Annual
$0
Total All Children (to age 18)
$0.00
Per Day
Cumulative Payment Projection
Milestone Timeline
Event
Calendar Year
Years From Now
Cumulative Paid
Note
⚠This projection assumes the current order amount continues unchanged. Support orders can be modified when income changes by 15% or more. Consult a family law attorney for state-specific rules and emancipation ages.
Frequently Asked Questions
How is child support calculated?
Most states use the Income Shares Model — both parents' incomes are combined, a basic obligation is determined from state guidelines tables, and the payer's proportional share is calculated. About 8 states use the Percentage of Income Model, where only the payer's income matters. Select your state above to use the correct formula.
Does shared custody reduce child support?
Yes, in most states. When the non-custodial parent has more than roughly 40% of overnight visits (about 146 nights/year), courts typically apply a credit. At true 50/50 custody, only the income difference typically drives payment. See the Custody & Scenarios tab for a full breakdown.
Is child support tax deductible?
No. Child support is not tax deductible for the paying parent and is not counted as taxable income for the receiving parent. This differs from alimony for divorces finalized before 2019.
When can child support be modified?
Either parent can request a modification when there is a substantial change in circumstances — typically a 15–20% change in income, a change in custody, or a significant change in the child's needs. Use the Modification Threshold Solver in the Scenarios tab to see what income level would trigger a review.
Until what age must child support be paid?
In most states, support continues until the child turns 18 or graduates high school (whichever is later). Some states extend to 19 or 21. New York allows support through college. Children with disabilities may receive support into adulthood. Enter child ages in the Long-Term Planner to model exact timelines.
Does the custodial parent's income matter?
In the Income Shares Model (used by ~40 states), yes — both incomes are combined. In the Percentage of Income Model (Texas, Illinois, Wisconsin, etc.), only the payer's income is used. This calculator automatically applies the correct model when you select your state.
What if the non-custodial parent refuses to pay?
Courts have strong enforcement tools: wage garnishment, license suspension, passport denial, tax refund interception, and contempt of court with potential jail time. Contact your state's child support enforcement agency (CSEA) for assistance.
What are add-on expenses?
Beyond basic support, parents share additional costs proportionally: health insurance premiums, uninsured medical/dental costs, and childcare for work or education. Enter these in the calculator — they are allocated according to each parent's share of combined income.
How to Use This Calculator
1
Select Your State
Choose your state to apply the correct calculation model — Income Shares or Percentage of Income — with state-specific rates.
2
Enter Incomes & Custody
Input monthly incomes, number of children, custody nights, and any add-on expenses like childcare and insurance.
3
Analyze & Plan
Review the Custody Scenarios tab for what-if analysis, and the Long-Term Planner for lifetime payment projections.
Income Shares ModelSupport = (Combined Income × Rate%) × Payer's Income Share
Percentage of IncomeSupport = Payer Net Income × State Rate% (+ add-ons)
Child support is a court-ordered payment from the non-custodial parent to the custodial parent to help cover the costs of raising a child. Unlike alimony, which involves significant judicial discretion, child support follows state guidelines that produce relatively predictable outcomes based on income and the number of children.
The majority of US states (approximately 40) use the Income Shares Model. This model assumes that a child should receive the same proportion of parental income they would have received if the family remained intact. Both parents' gross (or net, depending on state) incomes are combined, and a basic support obligation is determined from state guidelines tables. The non-custodial parent then pays their proportional share of that obligation.
Approximately 8 states — including Texas, Illinois, Wisconsin, Alaska, Mississippi, Nevada, North Dakota, and Arkansas — use the Percentage of Income Model. This simpler approach applies a fixed percentage solely to the non-custodial parent's income. Texas, for instance, sets support at 20% of net resources for one child, 25% for two, up to 40% for five or more, with a monthly net resources cap of $11,700 (as of September 2025). The custodial parent's income is not factored in.
Beyond the basic support amount, parents typically share additional child-related expenses proportionally: health insurance premiums for the child, uninsured medical and dental costs, and childcare costs incurred to allow work or education. These "add-on" expenses are generally allocated in proportion to each parent's share of combined income. Some states mandate these add-ons; others treat them as discretionary.
Child support orders can be modified when there is a substantial change in circumstances. Most states require a 15–20% change in income (or support amount) before a court will consider modification. Courts also examine changes in custody arrangements, major changes in the child's financial needs (such as new medical expenses or educational costs), and changes in either parent's financial situation due to remarriage, new children, or disability.