How Alimony Works: Formulas, Factors, and State Rules
Alimony (also called spousal support or maintenance) is a court-ordered financial payment from the higher-earning spouse to the lower-earning spouse following a divorce or legal separation. Its purpose is to recognize the economic partnership of marriage and help the lower-earning spouse maintain a reasonable standard of living while transitioning to financial independence.
Unlike child support, which follows detailed state-mandated formulas in all states, alimony calculation varies enormously. Some states — including Illinois, Massachusetts, New York, Colorado, and Texas — have enacted statutory formulas or binding guidelines. Most states, however, leave alimony entirely to judicial discretion, with courts weighing 10–17 statutory factors without a prescribed calculation.
The AAML formula (30% of payer's income minus 20% of payee's income) is the most widely used informal starting point among family law attorneys nationally. The Income Share approach (a percentage of the income difference) is used by several state guidelines and by online calculators for its transparency. The Ginsburg equalization formula, which splits the income difference in half, is used in some jurisdictions and produces higher estimates for large income gaps.
Duration of alimony generally correlates with marriage length. Short marriages (under 5 years) typically result in alimony lasting half the marriage or less. Moderate marriages (5–15 years) often produce rehabilitative alimony for 40–70% of the marriage duration. Long marriages (15+ years) may result in long-term or permanent alimony, particularly when one spouse maintained the household rather than a career.
A major tax change took effect for divorces finalized after December 31, 2018 (post-TCJA). Under the old rules, the paying spouse could deduct alimony and the recipient paid income tax on it — creating a net tax efficiency. Under the current rules, alimony is neither deductible for the payer nor taxable for the recipient. This effectively increases the real cost to the payer and removes the tax benefit that once facilitated settlements.
Alimony can be modified upon a substantial change in circumstances — a major income change, job loss, disability, retirement, or the recipient's remarriage or cohabitation. Building clear modification triggers into your divorce agreement is important. Bridge-the-gap and some durational orders are non-modifiable. Always work with a licensed family law attorney — this calculator provides educational estimates only.