Illinois child support calculator
Enter both parents' monthly gross income, the number of children and the overnights with you. See the estimate under Illinois's income shares guideline, step by step.
- The state's 2026 tables: the HFS schedule and net income table, effective March 20, 2026.
- Shared by income: each parent's share follows their part of the combined net income.
- Shared care counts once each parent has at least 146 overnights a year.
How Illinois calculates child support
Illinois has used an "income shares" guideline since July 1, 2017. The court finds each parent's monthly net income, adds them, looks up the basic child support obligation for that combined income and number of children in the state's schedule, and splits it by each parent's share of the combined income (750 ILCS 5/505(a)(1.5)). The parent who receives support is presumed to spend their share directly on the children.
The Department of Healthcare and Family Services (HFS) publishes the schedule and a table that turns gross income into "standardized" net income. Both were last updated with amounts effective March 20, 2026.
| 1. Net income | Standardized net income from the HFS table: gross income minus federal and state income tax and Social Security and Medicare, with standard withholding assumptions (HFS assumes head-of-household withholding for the parent with the majority of time). The parent with the majority of parenting time is presumed to claim the children (505(a)(3)(C)). |
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| 2. Schedule amount | Look up combined net income and the number of children (1 to 6) in the HFS Income Shares Schedule. |
| 3. Split by income | Each parent's share is their net income divided by the combined net income. |
| 4. Shared care | If each parent has 146 or more overnights a year, the amount is multiplied by 1.5 and each share is weighted by the other parent's time (505(a)(3.8)). |
| 5. Health insurance | The children's premium is shared by income and added or credited (505(a)(4)). |
Example: $5,000 and $3,000 gross, two children
These are the calculator's starting numbers: you earn $5,000 a month gross and have the children 100 nights a year; the other parent earns $3,000 and has the majority of the time.
| Your standardized net income ($5,000 gross, without the majority of time) | $3,921 |
|---|---|
| Other parent's ($3,000 gross, with the majority of time) | $2,468 |
| Combined net income | $6,389 |
| Schedule amount, two children (row $6,375.00 to $6,424.99) | $1,887 |
| Your share: $3,921 ÷ $6,389 = 61.37% × $1,887 | $1,158.07 |
With 146 nights a year with you, shared care applies: $1,887 × 1.5 = $2,830.50; your share × the other parent's 60% of nights = $1,042.27; the other parent's share × your 40% = $437.36; you pay the difference, $604.91.
Low incomes, high incomes and 2027 changes
If the paying parent's gross income is at or below 75% of the federal poverty guideline for one person ($997.50 a month with the 2026 guideline), the law presumes a minimum order of $40 a month per child, up to $120 in total. A parent with no income, or who receives only means-tested assistance, is presumed to get a $0 order (505(a)(3.3a), (3.3b)).
When combined net income is above the schedule's top row, the court decides the amount, but it can't be less than the top-row figure (505(a)(3.5)).
| From January 1, 2027 | Public Act 104-733 lowers the shared care threshold to 110 overnights, with an increase of 2% to 10% for a parent with 110 to 145 nights, and raises the minimum-order income line to 100% of the poverty guideline. The calculator uses the rules in force today by default and lets you switch to the 2027 rules. |
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| Child care and extras | The court may order both parents to share child care and extraordinary school or activity costs, usually by income share. These aren't part of the basic amount (505(a)(3.6), (3.7)). |
| Varying from the guideline | The court can order a different amount if the guideline would be inappropriate, after considering the children's needs and the parents' resources, and must explain why in writing (505(a)(3.4)). |
Questions people ask
How is child support calculated in Illinois?
Illinois uses income shares. Each parent's gross income is turned into net income, usually with the HFS standardized table. The combined net income and the number of children give a basic obligation from the HFS schedule, and each parent owes the share that matches their part of the combined income. The parent with fewer overnights pays their share to the other parent.
What is the 146-night rule in Illinois?
If each parent has the children for 146 or more overnights a year, Illinois uses its shared physical care formula: the basic obligation is multiplied by 1.5, each parent's share is multiplied by the other parent's percentage of overnights, and the parent who owes more pays the difference (505(a)(3.8)). From January 1, 2027, the threshold becomes 110 overnights.
How much is child support for one child in Illinois?
It depends on both parents' incomes. For example, if the paying parent has $1,000 a month in net income and the other parent $500, the 2026 schedule amount for one child at a combined $1,500 is $346, and the paying parent's two-thirds share is $230.67 a month.
What is the minimum child support in Illinois?
For a paying parent whose gross income is at or below 75% of the federal poverty guideline for one person, $997.50 a month in 2026, the law presumes $40 a month per child, up to $120 in total. For parents with no gross income, who receive only means-tested assistance, or who can't work because of a medically proven disability, incarceration or institutionalization, a $0 order is presumed instead (505(a)(3.3b)).
What is standardized net income?
It's net income from the HFS conversion table, which subtracts federal and Illinois income tax and Social Security and Medicare from gross income, using standard withholding assumptions that differ for the parent with and without the majority of parenting time. It is used unless the parents agree on, or the court decides to use, an "individualized" figure based on actual taxes (505(a)(3)(B)-(E)).
Updated November 8, 2026. Sources: 750 ILCS 5/505 (text in force through December 31, 2026; Public Act 104-733 takes effect January 1, 2027); Illinois HFS, Income Shares Schedule and Gross to Net Income Conversion Table, effective March 20, 2026; HHS 2026 poverty guidelines. An estimate, not legal advice: the court or HFS sets the actual amount. Not affiliated with HFS or any Illinois court.