Illinois Child Support Calculator – Accurate & Easy to Use

What Is the Illinois Child Support Calculator?

The Illinois Child Support Calculator is an online tool that estimates the amount one parent may owe the other under Illinois law. It follows the official Illinois Child Support Guidelines (750 ILCS 5/505), which use an “income shares” model.

That means both parents’ incomes, the number of children, and parenting time are considered—not just one parent’s earnings.

Important note: This calculator gives an estimate, not a court order. Judges may adjust the final amount based on unique family circumstances.

How Does the Illinois Child Support Calculator Work?

The calculator uses a step-by-step formula based on Illinois law. Here’s what it considers:

1. Gross Monthly Income

Both parents enter their monthly gross income (before taxes).

Example:

• Parent A earns $5,000 per month.
• Parent B earns $3,500 per month.

2. Net Income Adjustment

The calculator automatically adjusts gross income to net income (after taxes and Social Security/Medicare contributions).

3. Number of Children

The more children involved, the higher the basic support obligation.

Example:

• Support for 1 child is lower than support for 3 children.

4. Parenting Time (Overnights)

Parenting time plays a big role:

• If one parent has fewer than 146 overnights per year, the other parent usually pays more.
• If both parents have at least 146 overnights, the shared parenting formula kicks in, and obligations are adjusted.

5. Extra Costs (Add-Ons)

The calculator also includes:

• Health insurance premiums for children
• Work-related child care costs

These costs are shared based on each parent’s share of the combined income.

Example Calculation (Step-by-Step)

Let’s walk through a scenario.

• Parent A gross income: $5,000/month
• Parent B gross income: $3,500/month
• Number of children: 2
• Parent B has 120 overnights per year
• Health insurance: $200/month
• Child care: $0

The calculator estimates:

• Parent B pays Parent A a monthly support amount (based on income share and overnights).
• The payment will adjust if parenting time shifts to shared parenting (146+ nights).

Why Use the Illinois Child Support Calculator?

Using this tool has clear benefits:

• Quick Estimate: Get a ballpark figure in minutes.
• Transparency: Both parents can see how income and parenting time affect support.
• Planning Tool: Helpful for budgeting and negotiation.
• Fairness Check: Ensures the support follows Illinois guidelines.

Limits of the Calculator

While useful, remember:

• It’s only an estimate, not legally binding.
• Judges may adjust for special needs, education costs, or unusual expenses.
• It does not replace legal advice from a family law attorney.

Try It Yourself

Below is the Illinois Child Support Calculator you can use. Just enter:

• Your income
• The other parent’s income
• Number of children
• Parenting time (overnights)
• Extra costs (insurance, child care)

Then hit Calculate to see an estimated payment.