Alimony calculator Illinois: guideline maintenance
Alimony calculator, Illinois: enter both incomes and the length of the marriage, and this tool applies the state’s own guideline, 750 ILCS 5/504(b-1). That is 33 1/3% of the paying spouse’s net income minus 25% of the receiving spouse’s net income, capped at 40% of the couple’s combined net income, for a length set by a table in the statute. It is an estimate, not legal advice, and a judge can order something different.
Usually the higher earner. Gross means all income from all sources, before tax.
Gross income minus federal and state income tax, Social Security and Medicare. A pay stub times the number of paychecks is a fair start.
Enter 0 if there is no income.
After the same taxes. Enter 0 if there is no income.
The statute measures from the wedding to the date the case was filed.
Illinois maintenance calculator: the formula in the statute
Illinois law uses the word maintenance, not alimony. The rule is in Section 504 of the Illinois Marriage and Dissolution of Marriage Act (750 ILCS 5/504). It works in three steps.
- Check the guideline applies. The couple’s combined gross income must be under $500,000 a year, and the paying spouse must not already owe child support or maintenance from an earlier relationship. If either test fails, there is no formula.
- Work out the amount. Take 33 1/3% of the paying spouse’s net yearly income. Subtract 25% of the receiving spouse’s net yearly income. Then check the cap: the receiving spouse’s own net income plus the maintenance cannot come to more than 40% of the two net incomes added together. The smaller number wins.
- Work out the length. Multiply the length of the marriage, counted to the day the case was filed, by the factor in the table below.
Net income has a set meaning in Illinois. It is gross income minus federal and state income tax, Social Security and Medicare, worked out either from a standard table the state publishes or from the person’s actual taxes (750 ILCS 5/505). That is why the calculator asks for both gross and net income: gross decides whether the guideline applies, and net drives the amount.
Illinois alimony duration table
The length of guideline maintenance is the length of the marriage times one of these factors, copied from 750 ILCS 5/504(b-1)(1)(B).
| Length of the marriage | Factor |
|---|---|
| Less than 5 years | 0.20 |
| 5 years or more, less than 6 | 0.24 |
| 6 years or more, less than 7 | 0.28 |
| 7 years or more, less than 8 | 0.32 |
| 8 years or more, less than 9 | 0.36 |
| 9 years or more, less than 10 | 0.40 |
| 10 years or more, less than 11 | 0.44 |
| 11 years or more, less than 12 | 0.48 |
| 12 years or more, less than 13 | 0.52 |
| 13 years or more, less than 14 | 0.56 |
| 14 years or more, less than 15 | 0.60 |
| 15 years or more, less than 16 | 0.64 |
| 16 years or more, less than 17 | 0.68 |
| 17 years or more, less than 18 | 0.72 |
| 18 years or more, less than 19 | 0.76 |
| 19 years or more, less than 20 | 0.80 |
| 20 years or more | Length of the marriage, or indefinite |
So a 12-year marriage is in the 0.52 band, and guideline maintenance runs for 12 times 0.52, about 6.2 years. A marriage of 20 years or more has no factor: the judge orders maintenance for as long as the marriage lasted, or with no end date at all.
Three examples, run through the calculator above
Every figure below is produced by the same code the tool runs. The incomes are examples, not typical awards.
Linda, 56: married 24 years, part-time work
He earns $130,000 gross, about $95,000 net. She earns $26,000 gross, about $22,000 net. A third of his net is $31,667, minus a quarter of hers, $5,500. The 40% cap is $24,800, so the guideline is $24,800 a year, about $2,067 a month. Because they were married more than 20 years, the guideline length is either 24 years or indefinite, at the judge’s choice.
Carol, 52: married 15 years, earns her own salary
He nets $90,000 and she nets $30,000. The formula gives $22,500, but the cap stops it at $18,000 a year, about $1,500 a month, because her income plus maintenance cannot pass 40% of their combined $120,000. Fifteen years is in the 0.64 band, so the guideline length is about 9 years and 7 months.
Joan, 61: second marriage of 8 and a half years, no income
He nets $60,000 and she has no income. A third of his net is $20,000 a year, about $1,667 a month, under the cap of $24,000. Eight years is in the 0.36 band, so the guideline length is about 3 years and 1 month. At 61, that end date matters, which is why the length of maintenance belongs next to the retirement runway numbers.
When the Illinois guideline does not apply
There are four common cases where this Illinois alimony calculator can only tell you that the formula is off the table.
- Combined gross income is $500,000 a year or more.
- The paying spouse already owes child support or maintenance from an earlier relationship.
- The judge finds the guideline would be inappropriate for the case.
- There are children, and guideline maintenance plus child support would come to more than 50% of the paying spouse’s net income. The judge can then set a non-guideline amount.
In all of these the judge weighs the factors in 750 ILCS 5/504(a): each person’s income and property, needs, present and future earning capacity, time spent on the home that held back a career, the standard of living in the marriage, the length of the marriage, age and health, and others. The judge must also state in writing whether maintenance is fixed-term, indefinite, reviewable or reserved.
What this estimate cannot see
The guideline is the starting point the statute sets, not a promise. A court first decides whether maintenance is appropriate at any amount. Net income in a real case is worked out from documents, and arguments about bonuses, self-employment income or what someone could earn can move it a long way. Temporary maintenance paid while the case is going on may count against the length, at the judge’s discretion. If maintenance and the retirement accounts are being traded against each other, compare them with the Marital Share Estimator. For what a long marriage changes beyond support, read divorce after 20 or 30 years.
Comparing states? The California spousal support calculator uses a different formula, for temporary support only.
Frequently asked questions
How is alimony calculated in Illinois?
Illinois calls alimony maintenance. When the guideline applies, the yearly amount is 33 1/3% of the paying spouse’s net income minus 25% of the receiving spouse’s net income. The result is capped so the receiving spouse’s net income plus maintenance is no more than 40% of the couple’s combined net income. This is the rule in 750 ILCS 5/504(b-1)(1)(A).
How long does alimony last in Illinois?
Under the guideline, the length of the marriage when the case was filed is multiplied by a factor from a table in the statute. The factor starts at 0.20 for a marriage under 5 years and rises by 0.04 for each year, up to 0.80 for 19 to 20 years. For a marriage of 20 years or more, the judge orders maintenance for the length of the marriage or for an indefinite term.
Is alimony automatic in Illinois after a long marriage?
No. The statute says the court first decides whether maintenance is appropriate at all, after looking at factors such as each person’s income and property, needs, earning capacity, age, health and the standard of living during the marriage. Only if the answer is yes does the guideline set the amount and the length.
What if our combined income is $500,000 or more?
Then the guideline formula does not apply. It only covers couples whose combined gross income is under $500,000 a year, where the paying spouse has no child support or maintenance duty from an earlier relationship. Outside those limits the judge decides amount and length from the factors, with no formula.
Can an Illinois judge order a different amount than the guideline?
Yes. The judge can find that the guideline would be inappropriate and order a different amount or length. When that happens, the judge has to write down what the guideline would have been and the reasons for the difference. That is why any alimony calculator Illinois families use gives an estimate, not an answer.
Does maintenance stop if I remarry or live with someone?
Unless the parties agreed otherwise in writing and it is in the judgment, the duty to pay future maintenance ends when either person dies, when the person receiving it remarries, or when that person lives with another person on a resident, continuing conjugal basis. This is in 750 ILCS 5/510(c).
Sources: 750 ILCS 5/504, Maintenance (Illinois General Assembly), subsections (a), (b-1), (b-2), (b-3) and (b-3.5) · 750 ILCS 5/505, definitions of gross and net income · 750 ILCS 5/510(c), termination of maintenance. Text checked October 2026, current through Public Act 103-967, effective January 1, 2025. This calculator estimates the statutory guideline only. It is not legal advice, it cannot predict what a judge will order, and judges can deviate from the guideline.
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