There's no single alimony formula in the US. Most judges weigh incomes, marriage length, and earning capacity case by case. Where formulas do exist, they're income percentages: the common 30/20 guideline takes 30% of the payer's gross minus 20% of the recipient's, about $2,333 a month on $120,000 versus $40,000.
No, and this surprises almost everyone going through a divorce. Child support is formula-driven in all fifty states, so people assume spousal support works the same way. It doesn't. In most states, the statute hands the judge a list of factors, things like the length of the marriage, each spouse's income and earning capacity, age, health, contributions to the household, and the standard of living during the marriage, and the judge picks a number.
That discretion cuts both ways. Two similar couples in the same courthouse can walk out with very different orders. It also means most alimony cases settle: when nobody can predict the judge, a negotiated number both sides can live with beats rolling the dice. Formulas matter here anyway, because attorneys and mediators need somewhere to start, and the handful of states with real statutory math export their logic everywhere else as negotiation anchors.
The most widely quoted rule of thumb, associated with the American Academy of Matrimonial Lawyers, is simple: take 30% of the paying spouse's gross income and subtract 20% of the receiving spouse's gross income. If the result is negative, alimony is zero.
Run the numbers on a payer earning $120,000 and a recipient earning $40,000. Thirty percent of $120,000 is $36,000. Twenty percent of $40,000 is $8,000. The difference is $28,000 a year, which is about $2,333 a month. For duration, a common convention scales with the marriage: roughly 30% of the marriage length for very short marriages, half for mid-length ones, 75% for marriages of 10 to 20 years, and open-ended past 20. A 12-year marriage at the 75% factor points to 9 years of support, and 9 years at $28,000 totals $252,000. Numbers that size are exactly why it pays to run the math before negotiating.
Three big states wrote their formulas into statute, and they took three genuinely different approaches:
| State | Income base | Formula | Hard cap |
|---|---|---|---|
| Texas | Gross monthly | 20% of the payer's average gross monthly income | $5,000/mo, and usually 10+ years of marriage to qualify |
| New York | Gross, up to a cap | Lesser of 30% payer minus 20% payee, and 40% of combined income minus the payee's | Payor income counted up to about $228,000 (adjusts annually) |
| Illinois | Net (after tax) | 33.3% of payer's net minus 25% of payee's net | Recipient's net plus maintenance held to 40% of combined net |
Texas is the outlier on eligibility: court-ordered maintenance normally requires a 10-year marriage, with exceptions for family violence and disability, and the dollar cap means a high earner's exposure stops at $5,000 a month no matter what. The Texas alimony calculator shows how the 20% rule and the cap interact at different incomes.
New York's two-part formula quietly protects lower-paid payers: whichever calculation produces less is the one that applies. Illinois is the most intricate, since it runs on net income and then double-checks that the recipient doesn't end up with more than 40% of the couple's combined net. California belongs in this conversation too, with a twist: its 40%-minus-50% net formula only governs temporary support while the case is pending, and long-term support reverts to judicial discretion. The California alimony calculator walks through that split.
Enter both incomes and your marriage length once, then flip between the common guideline, Texas, New York, and Illinois to see the full range.
Alimony Calculator →Duration rules are just as varied as amount rules, and they lean heavily on marriage length. Illinois publishes an exact factor table: multiply the years married by a factor that starts at 0.20 for short marriages and climbs 0.04 per year to 0.80 at 19 years, with 20-year marriages eligible for indefinite support. A 12-year Illinois marriage gets 12 times 0.52, or 6.24 years. Texas uses hard ceilings instead: up to 5 years of payments for a 10-to-20-year marriage, 7 for 20 to 30, and 10 beyond that. New York publishes advisory ranges, 15% to 50% of the marriage length depending on how long it ran. And the old California rule of thumb, support for half the length of a shorter marriage, still shapes expectations far outside California.
Remember that most orders end early if the recipient remarries, and many states also cut support off at cohabitation with a new partner.
For decades, alimony was deductible for the payer and taxable income for the recipient, which made bigger awards cheaper in after-tax terms. The Tax Cuts and Jobs Act ended that for any divorce or separation agreement signed after December 31, 2018: no deduction for the payer, no taxable income for the recipient. Pre-2019 agreements keep the old treatment unless they're modified and expressly adopt the new rules.
One wrinkle: a few states didn't follow. California, notably, still allows the deduction and taxes the income on state returns. If you're also modeling the tax side, the child support calculator is the right companion for the kids' portion, which was never deductible, and the main alimony calculator notes the federal treatment beside every estimate.
It's a rule of thumb many family law attorneys use as a starting point: alimony equals 30% of the payer's gross income minus 20% of the recipient's gross income. On incomes of $120,000 and $40,000, that's $36,000 minus $8,000, or $28,000 a year. It isn't law in most places, but it anchors a lot of negotiations.
A minority. Texas, New York, and Illinois have statutory formulas or caps for the amount. California, Pennsylvania, and several others use formulas only for temporary support while the divorce is pending. Most states list factors, like marriage length, incomes, age, and earning capacity, and leave the number to the judge.
Yes, in every formula. The common guideline subtracts 20% of the recipient's gross income, Illinois subtracts 25% of net, and California's temporary guideline subtracts 50% of the lower earner's net. A recipient earning $40,000 against a $120,000 payer cuts the common guideline award from $36,000 to $28,000 a year.
Almost always. Statutory caps limit what a judge can order, not what spouses can negotiate. In Texas, for example, a court can't order more than $5,000 a month, but a settlement agreement for contractual alimony can go higher. Agreed amounts can also be made non-modifiable, which court orders usually aren't.