Illinois Child Support Calculator (Income Shares)
Enter both parents' net monthly incomes and the number of children to estimate Illinois child support by the income shares method.
Estimate only — not legal advice. This is an educational estimate using Illinois' official income shares schedule and the standard formula. It is not legal advice. It uses net incomes you enter and does not apply every adjustment a court makes — shared physical care (146+ overnights), health-insurance and childcare credits, multi-family or low-income adjustments. Consult an Illinois attorney or the HFS estimator for an official figure.
Illinois uses the income shares model: both parents' net incomes are combined, the state's Schedule of Basic Child Support Obligations gives the total support amount for that combined income and number of children, and each parent is responsible for their percentage share of it. The parent with less parenting time typically pays their share to the other.
⚠️ Double-check important results. This is an educational estimate, not professional advice — and where it uses a rate, bracket or fee, those change over time. Verify anything you'll rely on, especially in legal, financial, tax or medical matters, and read our full disclaimer. Think a result is wrong? Tell us so we can fix it.
How to Use This Calculator
Enter each parent's net monthly income and choose the number of children. The calculator combines the incomes, looks up the basic support obligation in Illinois' official schedule, and shows each parent's percentage share and dollar amount.
Use net income — gross pay minus taxes and certain deductions. Illinois provides a Gross to Net Income Conversion Table for this; if you only have gross figures, convert them first for an accurate result.
How the Calculation Works
The income shares model assumes children should receive the same proportion of parental income they would in an intact household. Both parents' net incomes are added together, and the state's Schedule of Basic Child Support Obligations converts that combined income and the number of children into a single basic support amount.
Each parent is then responsible for the percentage of that amount equal to their share of the combined income. The parent who has the children less of the time generally pays their share to the other parent.
combine net incomes → schedule gives basic obligation → split by income share
Worked Example
Parent 1 nets $3,000 a month and Parent 2 nets $2,000, so combined net income is $5,000, with 2 children. The official schedule gives a basic obligation of $1,674 at that income.
Parent 1's share is 3,000 ÷ 5,000 = 60%, or $1,004.40; Parent 2's is 40%, or $669.60. If Parent 1 is the parent with less parenting time, they would pay about $1,004 a month before any adjustments.
Assumptions, Limitations and Source
This tool uses Illinois' official Schedule of Basic Child Support Obligations (revised March 20, 2026) and the standard income shares formula. It takes the net incomes you enter and computes the base obligation only.
It does not apply the adjustments a court makes: the shared physical care formula when a parent has 146 or more overnights, credits for health insurance and childcare, or multi-family and low-income adjustments. Very high combined incomes above the schedule's top are set at the court's discretion. Confirm any real figure with an attorney or the HFS estimator.
- Uses the official 2026 Illinois income shares schedule
- Requires NET incomes (use the state's gross-to-net table to convert)
- Base obligation only — omits shared-care, insurance, childcare and low-income adjustments
- Not legal advice; the court sets the official amount
Rate source. The default value used above (2026 Illinois Schedule of Basic Child Support Obligations) comes from Illinois HFS — Schedule of Basic Child Support Obligations (rev. Mar 20, 2026). Rates like this change over time, so the field in the calculator is editable — overwrite it if it has changed.
Last verified 2026-07-31
When to Use an Illinois Child Support Calculator
Illinois parents and family-law professionals use this to estimate support using the state's official income-shares schedule. Run it when planning support, preparing for mediation, or checking an order against the guideline. It is an estimate of the base obligation; courts adjust for parenting time, health insurance, and childcare, so verify with an attorney.
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Open calculator →Frequently Asked Questions
How is child support calculated in Illinois?
Illinois uses the income shares model: both parents' net incomes are combined, the state schedule gives a basic obligation for that income and number of children, and each parent pays their percentage share of it based on their share of the combined income.
What is the income shares model?
It sets child support based on the combined income of both parents, on the principle that a child should get the same share of parental income they would if the parents lived together. Each parent contributes proportionally to their income.
Does Illinois use gross or net income?
Net income. Illinois publishes a Gross to Net Income Conversion Table to standardize the conversion. Enter net figures here; if you only have gross, convert them first for an accurate estimate.
Does parenting time change Illinois child support?
Yes. When a parent has 146 or more overnights a year, Illinois applies a shared physical care formula that can significantly change the amount. This tool gives the base obligation before that and other adjustments.
Is this the exact amount a court will order?
No. It estimates the base obligation from the official schedule. Courts adjust for shared care, health insurance, childcare and other factors, so confirm with an attorney or the HFS estimator.
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