Illinois Child Support Calculator (2026)
Estimate monthly child support under Illinois’ official income-shares guidelines. Enter both parents’ incomes and this tool applies the HFS Schedule of Basic Child Support Obligations (revised effective March 20, 2026), splits the obligation by income share, applies the shared-care offset when each parent has 146 or more overnights, and adds child care and health insurance costs.
Calculate Illinois Child Support
Before taxes. Use the parent you expect to pay support, or either parent — the higher earner is treated as the paying parent.
Nights the children sleep at the paying parent’s home. If both parents have 146 or more, the shared-care formula applies.
Work- or school-related child care for these children. Illinois courts subtract the federal child care tax credit first — enter your cost after any credit if you claim one.
The part of the premium that covers the children.
How to read this: the paying parent (the higher earner) owes their share of the basic obligation, adjusted for shared care when it applies, plus their share of the added costs. Net incomes are estimated from gross — see the assumptions below the calculator.
How Illinois Calculates Child Support
Illinois uses an income-shares model (750 ILCS 5/505, in effect since July 1, 2017). The guidelines estimate what parents living together would spend on their children at their combined income level, then divide that amount between the parents in proportion to income. The paying parent (the obligor) pays their share to the other parent. The statutory steps, under Section 505(a)(1.5), are:
- Find each parent’s monthly net income. Illinois law converts gross income to net using a standardized tax amount (federal and state income tax plus Social Security and Medicare), or an individualized tax calculation. This calculator estimates net income from the gross figures you enter.
- Add the two net incomes together to get the combined monthly net income.
- Look up the basic child support obligation on the HFS Schedule of Basic Child Support Obligations, using the combined net income and the number of children.
- Split the obligation by income share. A parent with 62% of the combined net income is responsible for 62% of the basic obligation.
- Apply the shared-care adjustment if it applies (Section 505(a)(3.8)): when each parent has the children for 146 or more overnights a year, the obligation is increased by half and offset between the parents, as explained below.
- Add the paying parent’s share of extra costs: work-related child care (Section 505(a)(3.7)) and the children’s health insurance premium (Section 505(a)(3.1)) are allocated between the parents in the same income proportions.
Basic obligation = HFS 2026 schedule amount for combined net income and number of children
Primary care: monthly support = payer’s share × basic obligation + payer’s share of child care and health premium
Shared care (146+ overnights each): monthly support = offset of (1.5 × basic obligation, split by share, each side × the other parent’s time %) + payer’s share of added costs
Worked Example: $5,000 and $3,000 Gross Monthly Incomes, 2 Children
| Step | Calculation | Result |
|---|---|---|
| Parent A net income (est.) | $60,000/yr gross minus est. federal tax $5,020 and FICA $4,590 | $4,199.17/mo |
| Parent B net income (est.) | $36,000/yr gross minus est. federal tax $2,140 and FICA $2,754 | $2,592.17/mo |
| Combined net income | $4,199.17 + $2,592.17 | $6,791.33/mo |
| Basic obligation (schedule, 2 children) | Interpolated between the $5,975 band ($1,808) and the $6,975 band ($1,969) | $1,939.43/mo |
| Parent A income share | $4,199.17 ÷ $6,791.33 | 61.83% |
| Base support | 61.83% × $1,939.43 | $1,199.17/mo |
| Added costs (payer’s share) | 61.83% × ($600 child care + $250 health premium) | $525.57/mo |
| Estimated support | $1,199.17 + $525.57 (73 overnights — no shared-care adjustment) | $1,724.74/mo |
Illinois Basic Child Support Obligation Schedule (Excerpt)
The full HFS schedule covers combined monthly net incomes in $50 bands — more than 520 rows. This excerpt reproduces the rows verified from the official schedule (2026 version, effective March 20, 2026), exactly as published. The calculator uses these verified rows and interpolates in a straight line between them, so results between rows are accurate to within a few dollars.
| Combined Monthly Net Income | 1 Child | 2 Children | 3 Children | 4 Children | 5 Children | 6 Children |
|---|---|---|---|---|---|---|
| $25.00–$74.99 | $12 | $18 | $21 | $24 | $26 | $28 |
| $975.00–$1,024.99 | $230 | $351 | $424 | $474 | $521 | $566 |
| $1,975.00–$2,024.99 | $461 | $702 | $848 | $948 | $1,042 | $1,133 |
| $2,975.00–$3,024.99 | $691 | $1,053 | $1,272 | $1,421 | $1,563 | $1,699 |
| $3,975.00–$4,024.99 | $921 | $1,378 | $1,656 | $1,849 | $2,034 | $2,211 |
| $4,975.00–$5,024.99 | $1,110 | $1,674 | $2,006 | $2,241 | $2,465 | $2,679 |
| $5,975.00–$6,024.99 | $1,211 | $1,808 | $2,142 | $2,393 | $2,632 | $2,861 |
| $6,975.00–$7,024.99 | $1,319 | $1,969 | $2,333 | $2,606 | $2,866 | $3,116 |
| $7,975.00–$8,024.99 | $1,444 | $2,137 | $2,507 | $2,801 | $3,081 | $3,349 |
| $8,975.00–$9,024.99 | $1,585 | $2,351 | $2,765 | $3,089 | $3,398 | $3,694 |
| $9,975.00–$10,024.99 | $1,686 | $2,499 | $2,938 | $3,282 | $3,610 | $3,924 |
| $14,975.00–$15,024.99 | $2,269 | $3,302 | $3,806 | $4,251 | $4,677 | $5,083 |
| $19,975.00–$20,024.99 | $2,784 | $4,119 | $4,836 | $5,402 | $5,942 | $6,459 |
| $24,975.00–$25,024.99 | $3,303 | $4,861 | $5,675 | $6,339 | $6,973 | $7,579 |
| $27,325.00–$27,374.99 | $3,547 | $5,210 | $6,069 | $6,779 | $7,457 | $8,106 |
Above the top of the schedule, Section 505(a)(3.5) lets the court use its discretion — but the basic obligation cannot be set lower than the amount at the schedule’s highest level. This calculator uses the highest verified band’s amount for combined incomes above it, so treat high-income results as a floor, not a cap: a court can order more.
Shared Physical Care: the 146-Overnights Adjustment
When each parent has the children for 146 or more overnights per year (about 40% of the year or more), Section 505(a)(3.8) presumes the children cost more to support across two fuller households, so the basic obligation is multiplied by 1.5. Each parent’s share of that larger obligation is then multiplied by the other parent’s percentage of parenting time, and the two amounts are offset — the parent who owes more on paper pays only the difference. The nearer the time split is to 50/50, the smaller the payment; where incomes are equal and time is equal, it can fall to zero.
This calculator applies the adjustment automatically when the paying parent’s overnights you enter (and the other parent’s remaining nights) are both 146 or more. Under the 2026 law there is no timeshare adjustment below 146 overnights — parenting time only changes the result once that line is crossed. A new graduated adjustment for 110–145 overnights is scheduled to take effect on January 1, 2027; it is not part of the 2026 guidelines and is not applied here.
Low Incomes: the $40 Minimum and $0 Orders
Illinois has no self-support reserve built into the schedule. Instead, Section 505(a)(3.3a) sets a rebuttable presumption for very low-income obligors — those whose gross income is at or below 75% of the federal poverty guidelines for a household of one: a minimum order of $40 per month per child, up to a maximum of $120 per month in total, divided equally among all the obligor’s children. And under Section 505(a)(3.3b), the presumption is a $0 order for a parent who has no gross income, receives only means-tested public assistance, or cannot work because of a medically proven disability, incarceration, or institutionalization.
This calculator shows a note when an estimate falls below the $40-per-child / $120-total range, but it does not change the calculated amount — a court applying the minimum rules could set a somewhat higher (or, in the $0-order cases, lower) figure than the plain schedule estimate.
How This Calculator Estimates Net Income
Courts start from each parent’s actual monthly net income. Illinois normally converts gross to net with the HFS standardized gross-to-net conversion table, which reflects federal and Illinois income tax and FICA, and assigns the children’s dependency exemptions to the parent with the majority of parenting time (which is why the official table has two net columns). The 2026 conversion table values are not reproduced in this tool, so it estimates net income by annualizing the gross figure you enter and subtracting only federal income tax — using the 2026 single-filer brackets and the $16,100 standard deduction — and Social Security and Medicare (FICA) at 7.65% combined (Social Security capped at the $184,500 wage base).
That means this tool’s net incomes usually run somewhat higher than a court’s standardized figures, because Illinois income tax and the other parent’s exemption effects are not deducted. The calculator also does not apply the adjustments Illinois allows for support paid for other children or for court-ordered spousal maintenance. For a result closer to a court’s, compare your pay stub’s actual net pay with the estimated net incomes shown in the results, and treat the final figure as an informed estimate rather than the exact guideline number.
