Illinois sets spousal maintenance by formula in most divorces: a fixed share of the payor’s net income, less a share of the payee’s, for a period pinned to the length of the marriage. The calculator below applies that statute — 750 ILCS 5/504(b-1) — to your numbers, including the 40% cap most estimators leave out. What it cannot do is tell you what your net income is, which is the part people actually litigate.
Illinois guideline estimate
Spousal Maintenance Calculator
Enter annual net income — gross pay less taxes and the deductions the statute allows, not take-home after voluntary withholding. Figures are an estimate under the statutory guideline, not an opinion on your case.
Enter both net incomes to see a guideline estimate.
This estimator applies the guideline in 750 ILCS 5/504(b-1) to the numbers you enter. It is general information, not legal advice, and it does not create an attorney-client relationship. What counts as “net income” is itself contested in many cases — particularly where a spouse is self-employed, paid on bonus or commission, or draws from a closely held business. Courts also deviate from the guideline. For an assessment of your own case, speak with a Chicago maintenance lawyer.
How Illinois Calculates Guideline Maintenance
The guideline amount is 33⅓% of the payor’s net annual income minus 25% of the payee’s net annual income. That result is then tested against a ceiling: maintenance, added to the payee’s own net income, cannot leave the payee with more than 40% of the parties’ combined net income. Where the incomes are far apart, that 40% cap — not the primary formula — often sets the final number, and a calculator that omits it will overstate the award.
The formula applies only when the parties’ combined gross annual income is under $500,000 and the payor has no child support or maintenance obligation from a prior relationship. Outside those bounds there is no formula at all. The court sets both amount and duration under the statutory factors in § 504(b-2), which is a different kind of case and usually a contested one.
How Long Maintenance Lasts
Duration is the length of the marriage multiplied by a statutory factor that climbs with each year: 0.20 for a marriage under 5 years, rising in steps to 0.80 for a marriage of 19 years. A 12-year marriage, for example, yields 12 × 0.52, or roughly 6 years and 3 months of maintenance.
At 20 years the schedule stops. For a marriage of 20 or more years the court has discretion to order maintenance for a period equal to the length of the marriage, or for an indefinite term — which is why long-marriage cases are argued on different ground than the arithmetic suggests.
Why "Net Income" Is the Contested Number
The formula is arithmetic. Its inputs are not. Net income under the statute is gross income less federal and state tax and a defined list of deductions — not take-home pay after voluntary 401(k) contributions, not what the pay stub says at the bottom. Two lawyers can run the same statute on the same household and reach materially different numbers because they characterized income differently.
That gap widens fast where a spouse is self-employed, compensated in bonus, commission, or equity, or takes distributions from a closely held company. Retained earnings, perquisites run through the business, and the difference between a salary and an owner’s draw are all live questions, and they change the maintenance figure before the percentages ever apply.
When Courts Depart From the Guideline
A guideline result is a starting point the court can leave. Judges deviate where the formula produces something unfair on the facts — a spouse who left the workforce to raise children, a payee with substantial non-marital assets, a payor whose income is about to change in a way the snapshot does not capture. The court must state its reasons, but it has the discretion.
Maintenance is also not fixed forever. A substantial change in circumstances supports modification, and the award terminates on remarriage or on the payee cohabiting with another person on a continuing conjugal basis. An award set correctly today can be the right target for a petition three years from now.