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Illinois Child Support Calculator
Estimate Illinois child support with the 2026 HFS income shares tables, including the standardized net income conversion and the 146-overnight shared care formula.
How to Use the Illinois Child Support Calculator
Using the Illinois child support calculator takes about a minute. Enter what you know, press Calculate Estimate, and read the breakdown under the result.
- Enter each parent's gross monthly income (before taxes) as Parent A and Parent B.
- Choose the number of children and the parent the children live with most of the time (the custodial parent).
- Add monthly work-related child care and the children's health insurance premium, if any, and say which parent pays them.
- If the children spend 146 or more overnights a year with each parent, enter the other parent's overnights so the shared physical care formula is used.
No account is needed. Your numbers are sent with the form, not placed in the page address, and this site does not store them. Treat the result as a planning estimate, then confirm it with the court or your state child support agency.
New Illinois Child Support Laws and Changes for 2026
Looking for new child support laws in Illinois for 2026 and 2027? Two things matter:
- 2026: the calculator uses the HFS 2026 addendum to the schedule of basic obligations and the 2026 standardized net income table.
- January 1, 2027: Public Act 104-0733 (SB 3524), approved on July 31, 2026, takes effect. It lowers the threshold for the shared-care formula from 146 overnights a year to 110, adds an adjustment for parents with 110 to 145 overnights, and changes the minimum support rule for low-income paying parents and the process for parents who are incarcerated. Until the effective date, this calculator applies the current 146-overnight rule.
Bill details are summarized from the Illinois General Assembly's record as reported by LegiScan; check ilga.gov and HFS for the final text.
How Illinois Calculates Child Support: The Income Shares Model
Illinois uses the income shares model under 750 ILCS 5/505. The idea is that children should receive the share of parental income they would have had if the family lived together, so both parents' incomes are combined and each pays their proportionate share. The Illinois Department of Healthcare and Family Services (HFS) publishes the two tables the calculation relies on, and this calculator uses the 2026 versions (addendum dated March 13, 2026, tables effective March 20, 2026).
- Convert gross to net. Illinois does not ask each parent to prove every deduction. The standardized net income table converts gross monthly income to a net figure. It has two columns: one for the parent with the majority of parenting time (who is treated as claiming the children) and one for the other parent. This is why the calculator asks where the children live most of the time.
- Add the two net incomes to get combined net income.
- Look up the basic obligation in the HFS schedule of basic obligations for that combined net income and number of children.
- Find each parent's share (their net income divided by combined net income).
- Add child care and health insurance costs and multiply the total by the paying parent's share. Costs the paying parent already pays directly are credited against that amount.
Both tables are updated each year, and Illinois law requires a full review of the guidelines every four years, with the current review due in 2026. We re-check the tables whenever HFS publishes a new addendum.
Illinois Child Support Examples
Example 1: Standard calculation, 2 children
The children live with Parent A, who earns $3,500 a month gross. Parent B earns $6,500. Child care is $400 a month, paid by Parent A.
- Parent A gross → net (standardized table): $3,500.00 → $2,845
- Parent B gross → net (standardized table): $6,500.00 → $4,920
- Combined net income: $7,765
- Basic obligation (schedule, 2 children): $2,079
- Parent A share / Parent B share: 36.6% / 63.4%
- + Child care costs: $400.00
- + Health insurance for the children: $0.00
- Total obligation: $2,479.00
- Parent B share: $1,570.73
Result: Parent B pays Parent A about $1,570.73/month.
Example 2: Same incomes with shared physical care (182 overnights)
If Parent B has the children 182 nights a year, the shared physical care formula replaces the standard one:
- Parent A gross → net (standardized table): $3,500.00 → $2,845
- Parent B gross → net (standardized table): $6,500.00 → $4,920
- Combined net income: $7,765
- Basic obligation (schedule, 2 children): $2,079
- Parent A share / Parent B share: 36.6% / 63.4%
- Shared physical care obligation (basic × 1.5): $3,118.50
- Parent A owes (share × Parent B's time): $569.72
- Parent B owes (share × Parent A's time): $990.67
- Difference paid after offset: $420.94
Result: Parent B pays Parent A about $420.94/month (shared physical care). Compare that with Example 1: shared parenting time lowers the transfer sharply because each parent is already supporting the children while they have them.
Example 3: Health insurance paid by the other parent, 1 child
Parent A has the child and earns $2,200; Parent B earns $5,200 and pays $150 a month for the child's health insurance.
- Parent A gross → net (standardized table): $2,200.00 → $1,861
- Parent B gross → net (standardized table): $5,200.00 → $4,070
- Combined net income: $5,931
- Basic obligation (schedule, 1 child): $1,206
- Parent A share / Parent B share: 31.4% / 68.6%
- + Child care costs: $0.00
- + Health insurance for the children: $150.00
- Total obligation: $1,356.00
- Parent B share: $930.52
- − Costs Parent B pays directly: -$150.00
Result: Parent B pays Parent A about $780.52/month.
These are calculator illustrations, not court rulings.
Illinois Schedule of Basic Obligations: Sample Amounts (2026)
These sample rows are taken from the 2026 HFS schedule. The figure is the basic obligation before child care, health insurance and the shares of each parent are applied.
| Combined monthly net income | 1 child | 2 children | 3 children | 4 children |
|---|
| $2,000 | $461 | $702 | $848 | $948 |
| $3,000 | $691 | $1,053 | $1,272 | $1,421 |
| $4,000 | $921 | $1,378 | $1,656 | $1,849 |
| $5,000 | $1,110 | $1,674 | $2,006 | $2,241 |
| $7,500 | $1,370 | $2,035 | $2,397 | $2,677 |
| $10,000 | $1,686 | $2,499 | $2,938 | $3,282 |
| $15,000 | $2,269 | $3,302 | $3,806 | $4,251 |
The full table has a row for every $50 band of combined net income and columns for up to six children.
Illinois Child Support With 50/50 or Shared Parenting Time
People searching for an Illinois child support calculator with 50/50 custody usually mean the shared physical care rule. It applies when each parent has the children for 146 or more overnights a year (about 40% of the time). The calculation:
- Multiply the basic obligation by 1.5 to reflect duplicated household costs.
- Each parent's portion is the shared obligation times their income share.
- Each parent's portion is then multiplied by the other parent's percentage of parenting time (overnights divided by 365).
- The two amounts are offset and the parent with the larger amount pays the difference.
Enter the overnights the children spend with the parent who does not have them most of the time. Below 146 overnights, the standard calculation is used. The estimate leaves out child care and health insurance in the shared formula, which a court allocates separately.
Frequently Asked Questions About Illinois Child Support
Is this the official Illinois child support calculator?
No. It is an independent estimator that uses the same HFS tables the state publishes (2026 versions). Only a court or HFS can issue an official amount. HFS explains the income shares model and publishes the schedule and net income table on its website.
How is child support calculated in Illinois?
Illinois uses income shares. Each parent's gross income is converted to a standardized net income, the two are added, the basic obligation is read from the schedule, and each parent pays their share of it plus child care and health insurance.
Does Illinois use gross or net income for child support?
Both, in sequence. You start with gross income, convert it to net with the HFS standardized net income table, and then the schedule is based on combined net income.
How does Illinois child support work with 50/50 custody?
When each parent has 146 or more overnights a year, the shared physical care formula applies: the basic obligation is multiplied by 1.5, each parent's share is multiplied by the other parent's parenting time, and the difference is paid. Enter the overnights in the calculator to see it.
How many overnights trigger shared physical care in Illinois?
146 overnights a year with each parent, which is roughly 40% of the year.
What is the standardized net income table?
It is an HFS table that converts gross income to net income using standard tax assumptions, with one column for the parent who has the majority of parenting time and another for the other parent. It saves the court from calculating each parent's actual taxes.
Are the Illinois tables updated every year?
Yes. HFS publishes an annual addendum for tax changes. The 2026 addendum is dated March 13, 2026 and the updated tables took effect March 20, 2026. The guidelines are also reviewed every four years.
Does this calculator include maintenance (alimony)?
No. It estimates child support only. Maintenance can affect incomes in real cases, so discuss both with the court or a family law attorney.
What if my income is outside the Illinois table?
The 2026 standardized net income table starts at $325 of gross monthly income and the schedule stops at its top row. Outside them this calculator says it cannot estimate rather than guess; ask the court or HFS how such incomes are handled.
Are there new child support laws in Illinois in 2026?
The 2026 HFS tables are current. In addition, Public Act 104-0733 (SB 3524), approved July 31, 2026, takes effect January 1, 2027 and lowers the shared-care threshold from 146 to 110 overnights per year. Until then the 146-overnight rule applies.
Official Illinois Child Support Resources
Published: October 10, 2026
Last reviewed: October 12, 2026
Researched and reviewed by Eric John, founder and editor, using official state statutes and guidance. How we build and check our calculators · Corrections
