Illinois family law calculators (2026)
Guideline estimates for Illinois, each built from the statute and shown step by step. Pick a calculator to start, or scan the key numbers below.
Child Support Calculator
Illinois Child Support Calculator
Illinois uses the income shares model: both parents' net incomes are combined, the basic obligation comes from the HFS schedule, and each parent owes a share proportional to income. Enter both incomes, the number of children and the overnights to see the guideline amount, including the shared physical care formula.
- Schedule revision
- March 20, 2026
- Shared care threshold
- 146 overnights
Alimony Calculator
Illinois Alimony Calculator
Illinois calls alimony maintenance and sets both the amount and the duration by statutory formula for most couples. Enter both net incomes and the length of the marriage to see the guideline amount, the 40% cap and how long payments are expected to last.
- Amount formula
- 33 1/3% minus 25%
- Cap
- 40% of combined net
Key 2026 figures in Illinois
Schedule revision (Child support)
HFS Schedule of Basic Obligations, combined net income up to about $27,375 per month.
March 20, 2026
Shared care threshold (Child support)
40% of the year for each parent triggers the 1.5 multiplier and offset.
146 overnights
Minimum order (Child support)
Per month, for a paying parent at or below 75% of the federal poverty guideline.
$40 / child
State tax used (Child support)
Illinois flat income tax in the standardized net income estimate.
4.95%
Amount formula (Alimony)
Of the payor's and payee's net incomes respectively.
33 1/3% minus 25%
Cap (Alimony)
The payee's income plus maintenance may not exceed 40% of both incomes combined.
40% of combined net
Duration factor (Alimony)
Multiplied by the length of the marriage; 20 years or more can be indefinite.
0.20 to 0.80
Applies below (Alimony)
Combined gross income; above that the court uses the statutory factors.
$500,000