The Alimony Formulas Agree on the Amount and Not on the Duration

Two of the three American formulas are the same formula

Write the two amount rules side by side and the coincidence stops being surprising. The AAML guideline says: take 30 percent of the payer's gross income minus 20 percent of the recipient's, then cap the result so that the recipient's own income plus the award does not exceed 40 percent of the two incomes combined. New York's statute says: take the lower of 30 percent of the payer minus 20 percent of the recipient, and 40 percent of the combined income minus the recipient's income. The AAML cap, rearranged, is exactly New York's second prong. So the two rules pick the same branch at the same moment. That moment has a name you can compute: 30P − 20R is smaller than 40P − 60R precisely when the recipient earns less than a quarter of the payer. Below that line both guidelines return 30 percent minus 20 percent; at or above it both return the 40 percent cap. There is no income pair anywhere in the plane where they disagree.

That leaves Massachusetts as the only genuinely different amount rule, and it is different in shape, not just in level: it is a percentage of the gap between the incomes rather than a difference of two percentages of two incomes. On 150,000 and 30,000 dollars the gap is 120,000, so 30 to 35 percent gives 36,000 to 42,000 a year against the other two guidelines' 39,000 — a band that straddles them. That near-agreement is worth stating plainly, because it is the opposite of how the three are usually described. If someone tells you the guidelines disagree wildly about how much, check whether they are actually disagreeing about how long.

Duration is where the money actually is

Take the same fourteen-year marriage and apply each guideline's own duration rule. AAML: marriages of ten to twenty years get a factor of 0.75, so 10.5 years. Massachusetts, under its durational limits, gives 70 percent of the length of a marriage of more than ten but not more than fifteen years: 9.8 years. New York's duration is advisory rather than binding and its range for a marriage of up to fifteen years is 15 to 30 percent: 2.1 to 4.2 years. On a payment of 39,000 dollars a year, that is 409,500 under AAML, 81,900 to 163,800 under New York, and 352,800 to 411,600 under Massachusetts. The gap between the highest and lowest total is a factor of five, and every one of those numbers came from the same two incomes.

This is why the tax question matters so much on the American side. For instruments executed after 31 December 2018 the Tax Cuts and Jobs Act repealed the deduction and the inclusion, so 39,000 dollars of alimony now costs the payer 39,000 dollars. Under the old rule, a payer in a 32 percent bracket bore 26,520 and a recipient in a 22 percent bracket kept 30,420. The nominal figure did not move; the payer's real cost rose by 47 percent, and over a 10.5-year AAML term the after-tax cost went from 278,460 to 409,500. Any pre-2019 order you are comparing against was priced in a different currency.

What a guideline number is, and what it is not

None of these three formulas is law in most of the United States. Alimony is decided state by state, and the majority of states have no binding statutory guideline at all: a judge weighs statutory factors — length of marriage, standard of living, contributions, health, earning capacity — and decides. Where a guideline does exist it is often advisory even then, and where it is binding it is binding on a defined slice of income. New York's statutory formula applies up to a cap on the payer's income which is adjusted for inflation every two years; above the cap the court decides on the factors. So a calculator's output is a starting point for a negotiation and an input to a settlement conference, not a prediction of an order.

It is also worth being precise about what the payer's income means in each rule. All three guidelines run on gross income, not net, and all three ignore the recipient's tax position — which after 2018 is no longer a rounding error, because the recipient now keeps the whole payment. If you are comparing an award made under a pre-2019 instrument with one being negotiated today, convert both to after-tax terms first. The same nominal dollar is worth about 47 percent more to a payer, and about 22 to 37 percent less to a recipient, depending on which side of the 2018 line the instrument sits.

The income cap, and why guideline numbers stop working at the top

New York's guideline applies to the payer's income up to a statutory cap that is adjusted for inflation every two years; income above it is left to the judge on the statutory factors. This is not a technicality. A guideline built as a linear percentage of income produces absurd results at high incomes because spending does not scale linearly with earnings, and the cap is how the statute admits that. Two consequences follow. First, on incomes above the cap, a calculator that ignores it will overstate the guideline figure, sometimes grossly. Second, the cap is a moving number: it is revised on a two-year cycle, so a figure quoted in an article, a template or a spreadsheet is only correct until the next adjustment. Check the current cap before you use any number that depends on it.

The same warning applies to every fixed number in this area. Massachusetts' durational percentages are in the statute and change only by amendment; New York's cap changes on a schedule; the AAML guideline is a 2007 document that has not been reissued. Treat a calculator as a way of seeing the shape of an outcome — how sensitive the answer is to each income, how much a year of duration is worth — rather than as a source of the outcome itself. The shape is stable. The constants are not.

Running the calculator without fooling yourself

Enter gross annual incomes, not net, and not household income — the guidelines run on each spouse's own gross. Set the length of the marriage in whole years measured to the date of the complaint or petition, since that is what the durational rules use. Switch the concurrent-child-support flag honestly: New York's guideline drops from the 30 and 20 percent pair to the 20 and 25 percent pair when the maintenance payer is also the non-custodial parent paying child support, and on 150,000 and 30,000 dollars that switch alone takes the guideline from 3,250 a month to 1,875, a 42 percent cut. It is not an option; it is a description of your case.

Then set the date of the agreement correctly, because that single field decides whether the payments are deductible and includible or neither. If the instrument was executed on or before 31 December 2018 and has not been modified with an express statement adopting the new rule, the old treatment survives. If it was executed after that date, it does not. Two identical orders on two sides of that line have different after-tax costs by nearly half, and no amount of arguing about the percentage will close that gap.

One marriage, six answers, and what travels between them

Line the six systems up and the differences are not differences of generosity. They are differences about what the payment is for. The American guidelines answer a question about income replacement. The French prestation compensatoire answers a question about a disparity created by the rupture, and pays it as capital. The German rules answer a question about whether the marriage produced a disadvantage that survives it. The Spanish and Portuguese rules ask whether the applicant can support themselves. The Italian divorce award, since 2018, asks what the applicant contributed and gave up. Same facts, five different questions, five different amounts — and none of them wrong.

What does travel between all six is the arithmetic of time and tax. A monthly figure means nothing until you multiply it by a duration and discount it; a nominal figure means nothing until you know who pays tax on it. Those two operations are the same everywhere, they are the ones a calculator can genuinely do for you, and they are the ones people skip. Do them first, on every offer, before arguing about the percentage.

Frequently asked questions

Why do the AAML and New York formulas give the same number?

Because they are the same formula written twice. AAML takes 30 percent of the payer's gross minus 20 percent of the recipient's, then caps the award so the recipient's income plus alimony does not exceed 40 percent of the combined income. New York takes the lower of that first expression and 40 percent of combined income minus the recipient's income — which is the AAML cap, rearranged. Both switch branches at the same point: when the recipient earns exactly a quarter of what the payer earns. On 150,000 and 30,000 dollars the recipient earns a fifth, so the cap does not bind and both return 39,000 a year. On 150,000 and 50,000 the recipient earns a third, the cap binds, and both return 30,000. The two guidelines differ on duration, on the income cap New York applies, and on legal force — not on the arithmetic of the amount.

How much did the 2017 tax law change what alimony really costs?

By about 47 percent of the payer's cost, without moving the headline number at all. The Tax Cuts and Jobs Act repealed Internal Revenue Code sections 71 and 215 for instruments executed after 31 December 2018: alimony is no longer deductible by the payer, and no longer included in the recipient's income. Take 39,000 dollars a year. Under the old rule a payer in a 32 percent bracket bore 26,520 after tax, and a recipient in a 22 percent bracket kept 30,420. Under the new rule the payer bears 39,000 and the recipient keeps 39,000. Over a 10.5-year term the payer's after-tax total goes from 278,460 to 409,500. Instruments executed on or before 31 December 2018 keep the old treatment unless they are modified with an express statement adopting the new rule, which is why the date of the agreement is a required input and not a formality.

Does the calculator predict what a judge will order?

No, and in most of the United States nothing could. Alimony is decided state by state; the majority of states have no binding statutory formula, and a judge weighs factors such as the length of the marriage, the standard of living established during it, each party's contributions, health, age and earning capacity. Even where a formula exists it may be advisory, and where it is binding it usually binds only up to a cap on income. What the calculator does is show the shape of the answer: how much a change in either income moves the number, how much a year of duration is worth, and how large the gap between the three published guidelines is on the same facts. Use it to prepare for a negotiation, then take advice from a family lawyer in your own state.

Is alimony the same thing as child support?

No, and mixing them up changes the arithmetic twice over. Child support belongs to the child and follows a state schedule, usually the income-shares model, which apportions a combined obligation between the parents. Alimony belongs to the former spouse and follows a different rule or no rule at all. They also interact: New York's maintenance guideline changes from 30 and 20 percent to 20 and 25 percent when the maintenance payer is also the non-custodial parent paying child support, and on 150,000 and 30,000 dollars that alone moves the guideline from 3,250 a month to 1,875. Child support is calculated first in most states, and the maintenance award is then computed on incomes adjusted for it — so run the child-support calculation before the alimony one, not after.

Why do the totals differ by a factor of five if the monthly figures are so close?

Because the total is the monthly figure multiplied by a duration, and the durations differ by a factor of five while the amounts differ by less than a fifth. On 150,000 and 30,000 dollars over a fourteen-year marriage: AAML gives 39,000 a year for 10.5 years, so 409,500. Massachusetts gives 36,000 to 42,000 for 9.8 years, so 352,800 to 411,600. New York gives 39,000 for an advisory 2.1 to 4.2 years, so 81,900 to 163,800. Highest total to lowest is 411,600 against 81,900 — five to one — and the monthly figures behind those totals were 3,000, 3,250 and 3,500. This is why negotiating hard over a hundred dollars a month while accepting the other side's duration is the wrong trade: one year of duration is worth 39,000 dollars, and a hundred dollars a month over ten years is worth 12,000.