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Child Support Calculator

State-specific estimates using Income Shares or Percentage of Income model — with custody impact analysis, sensitivity matrix, and long-term planner.

⚖ Educational estimates only — not legal advice. Child support is set by courts per your state's guidelines. Consult a family law attorney.
Income & Custody Details
Income Shares Model — both incomes
$
$
25.0% of year (91 nights)
$
$
Advanced Options
$
Co-pays, deductibles, dental — split pro-rata by income
Reduces payer's effective income (simplified approximation)
Estimated Monthly Support
$0
Enter details above
Formula
Basic Obligation = Combined Income × % Payer Share = Payer ÷ Combined + Add-ons − Insurance
Breakdown
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Combined Income
$0
Basic Obligation
0%
Payer's Share
$0
Child Care Add-On
$0
Medical Add-On
$0
Monthly Support
Income Split
Chart: cs chart a.
Custody Impact Analysis

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
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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
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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.
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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.

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Frequently Asked Questions

Basics 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.
Basics 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.
Basics 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.
Basics 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.
Basics 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.
Basics 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.
Basics 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.
Basics 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.
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Formula & Methodology

Income Shares Model
Support = (Combined Income × Rate%) × Payer's Income Share
Percentage of Income
Support = Payer Net Income × State Rate% (+ add-ons)
Custody Adjustment
If payer nights > 40% → Reduce by (custody% − 40%) × Basic Obligation
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Key Terms Explained

Income Shares Model
Both parents' incomes combined; obligation split proportionally. Used by ~40 states.
Percentage of Income
Support = fixed % of payer's income only. TX, IL, WI, AK and others.
Basic Support Obligation
The base child support amount from state guidelines tables, before add-ons.
Add-On Expenses
Childcare, healthcare, and extraordinary costs shared proportionally between parents.
Custodial Parent
The parent with whom the child primarily lives; typically receives support.
Non-Custodial Parent
The parent who pays child support; typically has fewer overnights.
Imputed Income
Income attributed to a voluntarily unemployed parent based on earning capacity.
Emancipation
When child support ends — typically at age 18 or graduation, varying by state.

Real-World Examples

E1

Example 1

Estimated total
$24,800

Example 1 would use this sample setup for the Child Support Calculator. The current example produces $24,800, and adjusting the calculator inputs above will update the estimate for a different scenario.

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Child Support in the US: How It's Calculated

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.