About the Alimony Calculator
This alimony calculator estimates spousal support (also called maintenance) from the two spouses’ incomes and the length of the marriage. It applies the guideline formulas that many courts and mediators start from — such as one-third of the higher earner’s income minus a quarter of the lower earner’s, capped so the recipient does not end up with more than 40% of the couple’s combined income — and then estimates how long payments might last.
Use it before a mediation session or a first meeting with a family-law attorney to get a realistic starting range, or to test how a change in income or a different formula affects the result. Both the paying and receiving spouse can use it to understand what is on the table.
Alimony law is state-specific and judges keep wide discretion, so treat the result as a planning estimate, not a prediction. The Illinois-style formula uses net income; many other guidelines use gross income. Since 2019, alimony under new US divorce agreements is neither deductible for the payer nor taxable to the recipient.
With the default inputs, the estimated monthly alimony is $1,750.00. Change any value above to recalculate instantly.
How to use the alimony calculator
- 1Enter the higher earner’s and lower earner’s yearly income.
- 2Enter the length of the marriage in full years.
- 3Choose the guideline formula closest to your state’s approach.
- 4Read the monthly amount, the estimated duration and the total paid.
- 5Compare formulas to see a realistic negotiating range.
Formula and method
Guideline alimony formulas subtract a share of the lower earner’s income from a share of the higher earner’s. The Illinois-style formula uses a = 33⅓% and b = 25% of net income; a widely used gross-income guideline uses 30% and 20%. The result is then capped so the recipient’s income plus support never exceeds 40% of the couple’s combined income. The simple “percentage of the difference” option applies your chosen share to the income gap with no cap.
Duration uses a statutory-style schedule: 20% of the marriage length for marriages under 5 years, rising by 4 percentage points per full year up to 80% at 19 years, and the full length of the marriage (or indefinite support) at 20 years or more. Real awards depend on state law and factors such as health, age, earning capacity and the standard of living during the marriage.
- A
- Yearly alimony
- Payer, Payee
- Yearly income of the higher and lower earner
- a, b
- Formula percentages for payer and payee
- factor
- Duration factor from the length of the marriage
Worked examples
$120k vs $45k, 12-year marriage (Illinois-style)
The raw formula gives $40,000 − $11,250 = $28,750 a year, but the 40% cap ($66,000 − $45,000) limits support to $21,000, or $1,750 a month. A 12-year marriage has a 52% duration factor, so support lasts about 6.2 years and totals roughly $131,040.
$150k vs $30k, 8 years, 30%/20% guideline
30% of $150,000 is $45,000, minus 20% of $30,000 ($6,000) gives $39,000. The cap is 40% of $180,000 minus $30,000 = $42,000, so it does not bind. At a 36% factor, an 8-year marriage suggests about 2.9 years of support, around $112,320 in total.
25-year marriage, 30% of the income difference
The income difference is $140,000; 30% of it is $42,000 a year, or $3,500 a month. After 25 years of marriage the schedule suggests support for the full length of the marriage — or indefinitely — so the estimate totals about $1.05 million over 25 years.
Frequently asked questions
How is alimony calculated?+
Each state is different. Some use a formula (for example Illinois: one-third of the payer’s net income minus a quarter of the recipient’s, capped at 40% of combined income), while others weigh factors such as need, ability to pay, marriage length, age, health and earning capacity without a fixed formula.
How long does alimony last?+
Duration usually scales with the length of the marriage. Short marriages may get support for a fraction of their length, while marriages of 20 years or more can lead to long-term or indefinite support. Remarriage or cohabitation of the recipient often ends it.
Is alimony taxable or tax deductible?+
For US divorce or separation agreements signed after December 31, 2018, alimony is not deductible by the payer and not taxable income for the recipient. Older agreements keep the previous rules unless they are modified to adopt the new treatment.
Can alimony be changed later?+
Most periodic alimony can be modified when there is a substantial change in circumstances, such as job loss, a large income change, retirement, disability, remarriage or cohabitation. Some agreements make support non-modifiable, so read the settlement carefully.
Is child support calculated before alimony?+
Often yes. In many states child support takes priority and the remaining income is used to consider alimony, or the two are calculated together. Use the child support calculator alongside this one to see the combined picture.
Results are general estimates and not legal advice. Laws vary by jurisdiction — consult a qualified attorney.