$120K vs $40K, 10 Years Married: Illinois's Alimony Formula Says $24K/Year for 4.4 Years
We ran a common scenario through the calculator: a 10-year marriage, one partner earning $120,000 net annually, the other $40,000. Illinois’s actual statutory maintenance formula — one of the only state-published alimony formulas in the country — puts the raw guideline amount at $30,000/year. But the statute’s income cap, which limits the lower earner’s total income to 40% of the couple’s combined net income, pulls that down to $24,000/year. Run through the duration bracket table, a 10-year marriage gets 44% of its length: about 4.4 years of maintenance.
The formula, applied step by step
| Step | Calculation | Result |
|---|---|---|
| Raw guideline | 33.33% × $120,000 − 25% × $40,000 | $30,000/yr |
| 40% cap check | 40% × $160,000 combined − $40,000 | $24,000/yr max |
| Capped amount | min($30,000, $24,000) | $24,000/yr |
| Duration bracket (10 yrs) | 10 × 44% | 4.4 years |
| Total estimated maintenance | $24,000 × 4.4 | $105,600 |
The cap matters more than people expect — in this scenario it reduces the raw guideline amount by 20%, and at higher income gaps the cap binds even harder. It exists specifically so maintenance doesn’t push the receiving spouse’s income above a defined ceiling relative to the couple’s combined resources.
Why Illinois’s formula gets cited everywhere, not just in Illinois
Most states treat alimony as a broad judicial determination — a judge weighs income, earning capacity, age, health, and the marriage’s standard of living, with no formula to point to. That makes “how much alimony will I pay/receive” genuinely hard to estimate anywhere outside the small number of states with codified guidelines. Illinois’s formula, adopted in 2015 and refined since, gets used as an illustrative reference point across finance and legal content nationally — not because it applies elsewhere, but because it’s one of the only concrete, published numbers to run against a real income scenario.
Where this framework breaks
- You’re not in Illinois. This is one state’s codified formula, useful only as a reference point for what a guideline-based approach looks like — it carries no legal weight anywhere else, and even similarly-labeled “guideline” states use different percentages or caps.
- Combined gross income exceeds $500,000. Above that threshold, Illinois’s own statute stops prescribing the formula and reverts to full judicial discretion.
- Grounds for deviation exist. Even in Illinois, a judge can deviate from the guideline for health, earning capacity, or standard-of-living factors this formula doesn’t weigh at all.
- Short marriages with similar incomes. Both the guideline amount and the duration shrink fast at the low end — the estimate may land close to $0 regardless of state.
What to actually do
- Treat this as a reference point for the conversation, not a prediction of an actual court order in your state.
- Research your own state’s approach — many states publish no formula at all, making a family-law attorney’s read on local judicial norms more valuable than any calculator.
- Pair this with a full divorce cost estimate, since alimony is explicitly excluded from most household-split calculations.
- In a settlement negotiation, treat a guideline-style estimate as a floor for discussion, not a target — actual awards depend on factors this formula can’t capture.
- Talk to a family-law attorney in your own state before relying on any number from this or any calculator.
For the household-split and legal-fee side of the financial picture, see why the real cost of divorce isn’t the lawyer, and for protecting premarital assets before any of this becomes relevant, see the prenup cost-benefit math.
Open the Alimony Estimator → and run your own incomes and marriage length.