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Montana Alimony Calculator (2026)

Under Montana Code Annotated § 40‑4‑203, courts may award maintenance only when the requesting spouse lacks sufficient property and cannot be self‑supporting through appropriate employment, and they decide each case by weighing statutory factors. This tool provides a rule‑of‑thumb estimate, not a legal determination.

Reviewed 2026-09-02 · Estimates only — not legal or financial advice.

Montana has no statutory alimony formula. Courts decide case by case under MCA § 40-4-203. The calculator below shows a widely used rule of thumb (the AAML guideline) as a negotiation starting point — it is not the law and a judge may land anywhere the factors justify.
Before taxes.
Before taxes.
The law behind this calculator: Montana maintenance factors — MCA § 40-4-203.

How Montana calculates it

  • Montana has no statutory alimony formula; judges apply the factors in MCA § 40‑4‑203 on a case‑by‑case basis
  • Start with 30% of the higher‑earning spouse’s gross annual income
  • Subtract 20% of the lower‑earning spouse’s gross annual income
  • Cap the result so the recipient’s total income does not exceed 40% of the combined income of both spouses
  • For duration, use 30% of the marriage length if under 3 years, 50% if 3–10 years, 75% if 10–20 years, and indefinite if over 20 years

Worked example

Using the rule‑of‑thumb for a 12‑year marriage where the higher‑earning spouse earns $100,000 per year and the lower‑earning spouse earns $40,000 per year, 30% × $100,000 equals $30,000 and 20% × $40,000 equals $8,000, giving a difference of $22,000 per year. The 40% cap reduces that to $16,000 per year, which works out to roughly $1,333 per month as a starting point. Because the marriage lasted 12 years, the duration guide for the 10‑20‑year band applies: 75% of 144 months equals about 108 months.

Frequently asked questions

Can I receive alimony in Montana if I own some property?

Montana law permits maintenance only when the requesting spouse lacks sufficient property and cannot be self‑supporting through appropriate employment, so limited assets may still qualify if they are insufficient for self‑support.

How is alimony taxed in Montana?

Alimony follows federal tax treatment. For divorces finalized after 2018, alimony is not deductible by the payor and not taxable to the recipient; Montana aligns with that federal rule.

How long might alimony last for a five‑year marriage in Montana?

The rule‑of‑thumb suggests 50% of the marriage length, so a five‑year (60‑month) marriage would guide an approximate 30‑month award, though the court can set a different period.

If the higher earner makes $200,000 and the lower earner $80,000, how is the estimate calculated?

Apply the rule‑of‑thumb: take 30% of $200,000, subtract 20% of $80,000, then apply the 40% combined‑income cap, and finally adjust the duration based on the marriage length using the same percentage bands.

Has Montana recently changed its alimony guidelines?

Montana has not adopted a statutory alimony formula; the guideline used here is a professional rule‑of‑thumb, not a statutory amendment, and there have been no recent changes to the statutory factors.

Is the calculation different in Billings, Missoula or Great Falls?

No. MCA § 40-4-203 applies statewide, so courts in Billings, Missoula, Great Falls and every other county start from the same guideline. Local practice can differ in how judges weigh deviation factors and in typical negotiated outcomes, but the formula on this page is the one used across Montana.

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