How is the alimony amount estimated?

A widely used guideline takes a percentage of the higher earner's income and subtracts a smaller percentage of the lower earner's income — the classic 30%/20% differential. The result is capped so the recipient's total income does not exceed a set share (commonly 40%) of the parties' combined income.

How is the duration of support estimated?

Many jurisdictions tie duration to marriage length: a fraction of the years married, increasing in long marriages, with marriages over roughly twenty years sometimes treated as indefinite or until retirement. This tool applies a stepped multiplier as an illustration.

Are these the official numbers for my state?

No. Only a handful of states publish formulaic guidelines, and many use the open-ended statutory factors instead — need, ability to pay, age, health, and standard of living. Treat the output as a negotiation anchor, not a court order.

Does this account for taxes or child support?

No. Since 2019, federal alimony is neither deductible nor taxable for new orders, and child support is calculated separately and usually takes priority. Model child support first, then revisit spousal support against the remaining income.

What is the 40% combined-income cap?

Several guideline formulas prevent the recipient's post-support income from exceeding about 40% of the couple's combined income, so the higher earner never ends up worse off than the recipient. This tool applies that cap and tells you when it binds.

What is the Spousal Support / Alimony Calculator?

Estimate spousal support amount and duration from the income gap, marriage length, and standard-of-living factors. Models common guideline formulas — a percentage of the income differential for the amount and a length-of-marriage multiplier for duration. It runs free in your browser on Gera Tools, with nothing uploaded.

Spousal Support / Alimony Calculator

Name: Spousal Support / Alimony Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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A spousal support calculator estimates both the monthly amount of alimony and its likely duration from the two key drivers most guideline formulas share: the income gap between the spouses and the length of the marriage. While only some states publish a formula, the patterns below are common negotiation anchors used by family law practitioners to set realistic expectations before mediation.

How it works

For the amount, the tool uses the classic income-differential formula: take roughly 30% of the higher earner’s gross income and subtract about 20% of the lower earner’s income. The positive difference is the indicated monthly support. A cap then applies — the recipient’s total income (their own plus support) is held to no more than 40% of the couple’s combined income — which prevents the formula from over-shifting income.

For the duration, the tool multiplies the years married by a stepped factor that grows with longer marriages: shorter marriages yield a small fraction of their length, mid-length marriages a larger fraction, and very long marriages can be treated as long-term or indefinite, often until retirement age.

Amount = max(0, 0.30 × high income − 0.20 × low income), capped at 40% of combined income.
Duration ≈ years married × a multiplier that rises with marriage length.

Worked example

Suppose Spouse A earns $8,000/month and Spouse B earns $3,000/month, and they were married for 10 years.

Step 1 — differential: 0.30 × 8,000 − 0.20 × 3,000 = 2,400 − 600 = $1,800/month.
Step 2 — cap check: recipient total = 3,000 + 1,800 = $4,800. Combined income = $11,000. Cap = 0.40 × 11,000 = $4,400. The cap binds, so support is trimmed to $4,400 − $3,000 = $1,400/month.
Step 3 — duration: for a 10-year marriage a mid-tier multiplier (around 0.4–0.5) suggests roughly 4–5 years of support.

That is an illustrative scenario. A 20-year marriage with the same income split would likely push toward indefinite or long-term support rather than a fixed term.

What the tool does not capture

State-specific deviations. California’s DISSO-MASTER system, New York’s income-sharing model, Texas courts’ relatively stingy treatment of alimony, and states with no formula at all will diverge from this estimate.
Earning capacity vs actual income. Judges can impute income to a spouse who is voluntarily underemployed, which changes both sides of the formula.
Child support interaction. Child support is calculated first and affects the income available for spousal support.
Tax treatment. For divorce decrees signed after 31 December 2018, alimony is not deductible by the payer nor taxable to the recipient. Pre-2019 orders follow the old rules.

How to use the output effectively

Treat this as a negotiation anchor — a starting number both sides can react to. Mediators and collaborative lawyers often run the income-differential formula early in settlement discussions to anchor realistic expectations. Courts are not bound by any formula, but having a principled estimate shifts conversations from emotional positions toward financial realities.

Always model child support first (using a state-specific calculator), then come back to spousal support with the adjusted net incomes. The interaction between the two can change which cap binds and by how much.