Alimony Formulas: Why Most States Have No Single Equation

Ask a family lawyer for an "alimony formula" and you'll usually get a shrug. Unlike child support — which 38 states calculate using a published income-shares schedule — most states have no single equation for spousal support. Instead, alimony is decided by a list of statutory factors, with the amount and duration left to judicial discretion. Practitioners nonetheless rely on rough formulas to set expectations and frame settlement negotiations. This guide covers the AAML 30/20 formula with a detailed worked example, a state-by-state duration table (including California's indefinite rule for 20+ year marriages, Florida's 2023 reform capping at 75% of marriage length, and Texas's 10-year maximum for 30+ year marriages), the New York advisory schedule, the TCJA tax-treatment change for post-2018 divorces, and modification standards.

Why most states reject a single formula

Alimony exists to address economic disparity between spouses after divorce — a goal that resists a one-size formula. A 25-year marriage where one spouse worked and the other raised children looks nothing like a 3-year childless marriage between two earners, yet both can produce an alimony claim. State legislatures have generally concluded that a list of factors, weighed by a judge, produces fairer outcomes than a fixed equation.

Every state's alimony statute therefore enumerates factors. California's Family Code § 4320 lists 14 of them — including the length of the marriage, the marital standard of living, each spouse's earning capacity, the contribution of each to the other's education or career, the age and health of the parties, and any history of domestic violence. New York's Domestic Relations Law § 236(B)(6) lists a similar set of factors without prescribing a dollar figure. Illinois (750 ILCS 5/504), Pennsylvania (23 Pa.C.S. § 3701), and most other states follow the same pattern.

The result is that lawyers and mediators use formulas as benchmarks rather than rules. The benchmark may come from a statute in some states, from an advisory schedule in others, and from a professional guideline everywhere else.

The AAML formula and the 30/20 rule — worked example

The most widely cited rough alimony formula in the United States comes from the American Academy of Matrimonial Lawyers. Published in 2007 as a proposed guideline for permanent (long-term) alimony, the AAML formula is:

Annual alimony = 30% of payor's gross income − 20% of payee's gross income

The formula also includes a cap: the recipient's total income (their own earnings plus the alimony) should not exceed 40% of the couple's combined gross income. If it would, the alimony amount is reduced to keep the recipient below that ceiling.

Detailed worked example. A couple divorces after 14 years of marriage. Husband (the payor) earns $185,000/year gross as a senior software engineer. Wife (the payee) earns $42,000/year as a part-time teacher. They have two children, but child support is computed separately; the alimony calculation focuses only on the spouses' incomes.

Step 1 — Raw formula: 30% × $185,000 − 20% × $42,000 = $55,500 − $8,400 = $47,100/year, or about $3,925/month.

Step 2 — Apply the 40% cap. Combined gross income = $185,000 + $42,000 = $227,000. 40% of combined = $90,800. Payee's total income if alimony is $47,100 = $42,000 + $47,100 = $89,100. The payee's total income ($89,100) is below the 40% cap ($90,800), so the cap does not bind. Alimony is $47,100/year.

Step 3 — Sanity check the payor's remaining income. Payor's gross: $185,000. After alimony: $185,000 − $47,100 = $137,900. The payor retains roughly 60.7% of combined income — exactly the formula's intended result.

Step 4 — Duration. The AAML formula does not specify duration; that is left to state law. In a 14-year marriage under typical state duration patterns (30–50% of marriage length for mid-length marriages), expect a durational alimony award of 4 to 7 years — long enough for the payee to acquire education or training and re-enter the workforce at a higher income.

Compare the same formula applied to a high-income case. Payor earns $400,000/year; payee earns $40,000/year. Raw formula: 30% × $400,000 − 20% × $40,000 = $120,000 − $8,000 = $112,000/year. Payee's total income if alimony is $112,000 = $152,000. Combined gross income = $440,000; 40% cap = $176,000. The payee is below the cap, so the formula stands. But in many states (Massachusetts, New Jersey, New York), the court would apply a state-specific cap on income considered for the formula — typically around $250,000 to $350,000 — and apply discretion above the cap. The state cap often produces a substantially lower alimony figure than the raw AAML math.

The AAML formula is not law in any state, but it is referenced in court decisions and is the default math used by mediators and collaborative lawyers. It also matches what many practitioners describe as a "rule of thumb" — that alimony typically falls between one-quarter and one-third of the payor's gross income minus the payee's gross income, capped at a level that leaves the payor with roughly 60% of combined income after paying.

States that have actually adopted formulas

A handful of states have moved toward more prescriptive approaches. Massachusetts alimony reform (Alimony Reform Act of 2011, M.G.L. c. 208 §§ 48–55) provides a formula tied to the type of alimony. For general term alimony in a marriage of 5 years or less, the duration is capped at 50% of the marriage length; for 10–15 years, 60–70%; for 20 years or more, alimony can continue indefinitely. The amount under the statute is "not to exceed the recipient's need or 30 to 35 percent of the difference between the parties' gross incomes." Trial courts commonly use the midpoint of that range — 33% of the difference — for general term alimony. The Massachusetts alimony guidelines summarize the framework.

New Jersey amended its alimony statute in 2014 (N.J.S.A. 2A:34-23). For marriages of less than 20 years, the duration of alimony cannot exceed the length of the marriage except in exceptional circumstances. There is no statutory formula for amount, but New Jersey practitioners commonly use the AAML formula as a starting point.

Pennsylvania adopted a formula for the duration of alimony in 2014. Under 23 Pa.C.S. §3701, for marriages of 1–2 years, alimony duration is capped at 15% of the marriage length; for 3–8 years, 25%; for 9–15 years, 35%; for 16–20 years, 45%; for marriages of 20+ years, the cap is 50%. Amount remains discretionary under the §3701 factors, but Pennsylvania also maintains a separate guideline for alimony pendente lite (temporary support during the divorce) under Pa.R.C.P. 1910.16-4 — that guideline formula is roughly 33% of the payor's net income minus 25% of the payee's net income, with a cap that the payee's total income not exceed 40% of combined net.

Texas takes a different approach: it limits both amount and duration by statute. Under Texas Family Code § 8.055, contractual or court-ordered maintenance cannot exceed the lesser of $5,000 per month or 20% of the payor's gross monthly income. Duration is capped based on marriage length: 5 years for a 10–20 year marriage, 7 years for a 20–30 year marriage, 10 years for a 30+ year marriage (Texas Family Code § 8.054). Permanent alimony does not exist in Texas.

State-by-state duration rules (2024)

The table below summarizes the duration caps in states that have codified them. States without statutory duration caps (such as California, where long-term alimony can be indefinite for marriages of 10+ years) are noted.

New York's advisory schedule formula

New York took an unusual middle path. The 2015 alimony reform (DRL §236(B)(5-a) for temporary maintenance and §236(B)(6) for post-divorce maintenance) introduced an advisory schedule with two income cap tiers. For combined income up to the cap (currently $228,000/year as of March 2024 under the 2020 advisory guidelines update), the formula is:

Guideline maintenance = 25% of payor's income − 10% of payee's income, capped at 40% of combined income.

For income above the cap, courts use discretion guided by statutory factors. Worked example: payor earns $150,000/year; payee earns $50,000/year. Combined = $200,000 (under the cap). Formula: 25% × $150,000 − 10% × $50,000 = $37,500 − $5,000 = $32,500/year in maintenance, or about $2,708/month. Check the cap: payee's total income if alimony is $32,500 = $50,000 + $32,500 = $82,500. 40% of combined = $80,000. The payee exceeds the cap, so alimony is reduced to $30,000/year ($50,000 + $30,000 = $80,000 = 40% cap).

Duration is also formula-driven under the NY advisory schedule: for a marriage of 0–3 years, guideline duration is 15% of the marriage length; for 3–6 years, 25%; for 6–10 years, 35%; for 10–15 years, 40%; for 15+ years, 30% to 50% (advisory). The 15+ year category gives the court discretion to set duration anywhere in that range based on the factors.

Florida enacted significant reform in 2023. SB 1922, signed by Governor DeSantis in June 2023 and effective July 1, 2023, eliminated permanent alimony entirely — replacing it with durational alimony as the longest form. Durational alimony is capped based on marriage length: marriages of 3–10 years, 50% of the marriage length; 10–20 years, 60%; 20+ years, 75%. Amount remains discretionary under Florida Statute § 61.08, but the statute now also allows modification or termination when the payor retires in good faith at a reasonable age.

California remains strictly a discretionary state for long-term alimony. Family Code §4320 lists the factors; amount and duration are left to the judge. For temporary spousal support, however, many California counties use a guideline formula — Santa Clara County's formula (40% of payor's net minus 50% of payee's net, capped at 50% of combined) is widely cited and used as a starting point. Long-term alimony in California is theoretically indefinite for marriages of 10+ years (Family Code §4336), but the court retains jurisdiction to modify or terminate. The California Courts self-help guide describes the framework in plain language.

How the TCJA changed alimony taxation

The Tax Cuts and Jobs Act of 2017 (Public Law 115-97, § 11051) made one of the largest changes to alimony in decades. For divorce decrees executed after December 31, 2018, alimony is no longer deductible to the payor and no longer taxable to the recipient. For decrees executed before that date, the prior rule (deductible above-the-line to the payor, taxable as ordinary income to the recipient) continues — unless the decree is modified after 2018 and the modification expressly adopts the new rule. The IRS alimony topic and IRS Publication 504 describe the current rules in detail.

The change affects negotiation dynamics. Before 2019, a high-bracket payor could deduct alimony against their own income while a lower-bracket recipient paid tax at their lower rate — a federal subsidy of the alimony transfer. Post-2019, the alimony dollar is taxed entirely to the payor before transfer, so the same gross payment produces less after-tax cash for the recipient.

Worked example: a payor in the 32% federal bracket agrees to pay $4,000/month in alimony. Under the pre-2019 rule, the after-tax cost to the payor was $4,000 × (1 − 0.32) = $2,720/month; the recipient (in the 22% bracket) received $4,000 × (1 − 0.22) = $3,120/month after tax. The federal government effectively subsidized $880/month of the transfer. Under the post-2019 rule, the payor's after-tax cost is the full $4,000/month (no deduction), and the recipient receives the full $4,000/month (no tax). To produce the same $3,120/month after-tax cash to the recipient under the new rule, the payor must agree to pay $3,120/month — but the payor's after-tax cost is then $3,120, not $2,720. The same dollar-level outcome requires negotiation on both sides.

Practitioners typically grossed-up payments during the transition window and now negotiate with after-tax dollars in mind. The 2018 IRS Publication 504 is the last version describing the pre-TCJA rules.

The TCJA change does not affect child support (which was never taxable or deductible), property settlements (also non-taxable), or temporary support payments that are properly characterized as alimony. It also does not affect payments made under pre-2019 decrees — those retain their original tax treatment unless modified to adopt the new rule.

How duration is determined when there is no formula

Even in states without a duration formula, courts follow recognizable patterns. Short marriages (under 5 years) usually produce short-term or transitional alimony, often 1–3 years, designed to help the recipient re-establish independence. Mid-length marriages (5–15 years) commonly produce rehabilitative or durational alimony for a defined period — often 30–50% of the marriage length. Long marriages (20+ years) can produce indefinite or "permanent" alimony in states that allow it, though the trend has been away from true permanency.

The "rehabilitative" label matters. Rehabilitative alimony is meant to support the recipient while they acquire education or training to become self-supporting; the order usually includes a specific plan and review date. Reimbursement alimony, recognized in some states, compensates a spouse who contributed substantially to the other spouse's education or earning capacity — a classic example being a spouse who worked to put their partner through medical school.

Modification standards — substantial change in circumstances

Modification is generally available unless the decree specifically designates alimony as "non-modifiable." Most states allow modification on a substantial change in circumstances — a standard that requires more than a temporary setback but less than a permanent catastrophe. Common triggers include:

• Job loss or involuntary income reduction — a payor who loses their job through no fault of their own can typically obtain a temporary or permanent reduction. The reduction is not automatic; the payor must demonstrate good-faith job search efforts and document the income change.
• Illness or disability — a payor who becomes disabled and qualifies for SSDI may have alimony reduced to reflect the lower disability income.
• Retirement — Florida's 2023 reform added explicit retirement provisions, allowing modification or termination when the payor retires in good faith at a reasonable age (typically Social Security Full Retirement Age, 67). New Jersey's 2014 reform added a rebuttable presumption of termination when the payor reaches full Social Security retirement age.
• Cohabitation of the recipient — most states treat recipient cohabitation as a basis for modification or termination, on the theory that the recipient's economic need decreases when sharing household expenses with a new partner. Some states require proof of economic interdependence (shared expenses, joint accounts); others presume modification based on the cohabitation itself.
• Material change in either party's income — a payor whose income doubles through promotion may face an upward modification; a recipient whose income triples may face a downward modification or termination.

Modification requires a formal petition, financial disclosures from both parties, and a hearing. The new amount is generally prospective only — past-due alimony continues to accrue at the old rate until the modification is entered. Some states allow retroactive modification to the date of the petition (rather than the date of the order), but no state allows retroactive modification to a date before the petition was filed.

Cohabitation and termination triggers

Most state statutes treat recipient cohabitation as a basis for modification or termination, on the theory that the recipient's economic need decreases when sharing household expenses with a new partner. The standard varies: some states require proof of economic interdependence (shared expenses, joint accounts); others presume modification based on the cohabitation itself. California Family Code §4323 creates a rebuttable presumption of decreased need upon cohabitation. New Jersey N.J.S.A. 2A:34-23(n) similarly permits termination or suspension.

Death and remarriage are universal termination triggers — every state statute terminates alimony on the recipient's remarriage unless the decree says otherwise, and alimony ends on the death of either party unless secured by life insurance or a trust. Payors often negotiate a life insurance policy on themselves as security for the alimony obligation, especially in long-term cases.

Practical estimation when no formula applies

For a ballpark estimate in a state without a formula, the AAML 30/20 rule remains the most useful starting point, with the recipient's total-income share capped at 40% of combined. Apply the state-specific duration pattern (30–50% of marriage length for mid-length marriages, indefinite only for long marriages in states that allow it), then adjust for the statutory factors most relevant to the case: length of marriage, disparity in earnings, recipient's earning capacity, contributions to the payor's career, and any special needs.

For tax planning, the post-2019 rule means both parties should compute after-tax cash flow before settling. A $4,000/month alimony payment under the new rule costs the payor more in after-tax dollars than the same payment under pre-2019 law, and yields less after-tax cash to the recipient — both effects should be reflected in the negotiated amount.

Takeaways

Alimony in the U.S. is mostly a discretionary, factor-driven system with formulas used as benchmarks rather than rules. The AAML 30/20 formula is the most common practitioner tool, but only a handful of states — Massachusetts, New Jersey, Pennsylvania, Texas, New York, and post-2023 Florida — have actually codified amount or duration formulas. The 2019 TCJA change ended the federal alimony tax deduction for new decrees, which materially shifted negotiation economics. Modification is available on a substantial change in circumstances but is generally prospective only, so file promptly. For a working estimate, run the AAML math, check the state-specific duration pattern from the table above, and then adjust for the statutory factors that apply.