Estimate the alternative minimum tax: start from regular taxable income, add back the AMT adjustments (standard deduction or state and local taxes, the ISO bargain element and other items), apply the exemption and phase-out, and compare the 26%/28% tentative minimum tax with your regular tax.
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Filing details
$
Form 1040 line 15 (after deductions).
$
Deduction you take
$
Added back for AMT (Schedule A line 5e).
AMT adjustments
$
(Fair market value − strike price) × shares exercised and held at year end.
$
Private activity bond interest, depreciation differences, etc.
$
Leave blank to compute from the brackets.
Enter your values to see the result.
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How to use the AMT Calculator
Pick the tax year and filing status.
Enter your regular taxable income and how much of it is long-term gains or qualified dividends.
Choose standard or itemized; if itemizing, enter the state and local taxes you deducted.
Enter the ISO bargain element for options exercised and held at year end, plus any other AMT adjustments.
Calculate to see AMTI, the exemption, the tentative minimum tax and the AMT owed, plus how much more ISO you could exercise before AMT starts.
AMT formula (Form 6251)
AMTI = regular taxable income + standard deduction (or itemized state and local taxes) + ISO bargain element + other adjustments and preferences.
Exemption = base exemption − phase-out rate × (AMTI − phase-out threshold), not below $0.
Tentative minimum tax = 26% × first breakpoint of (AMTI − exemption) + 28% × the rest, with capital gains and qualified dividends at their usual rates.
AMT = tentative minimum tax − regular tax, if positive.
AMT figures by year
Item
2025
2026
Exemption, single / head of household
$88,100
$90,100
Exemption, married filing jointly
$137,000
$140,200
Exemption, married filing separately
$68,500
$70,100
Phase-out starts, single / HOH / MFS
$626,350
$500,000
Phase-out starts, joint
$1,252,700
$1,000,000
Phase-out rate
25%
50%
28% rate starts (MFS: half)
$239,100
$244,500
Sources: IRS Rev. Proc. 2024-40 and 2025-32; P.L. 119-21 reset the phase-out thresholds and raised the phase-out rate to 50% starting in 2026.
Common AMT triggers
Exercising and holding ISOs: the most common trigger today. Spreading exercises over several years, or exercising early in the year so you can sell in the same year if the price falls, limits the exposure.
High state and local taxes when itemizing, because SALT is not deductible for AMT.
Private activity bond interest, which is tax-free for regular tax but taxable for AMT.
Large one-time income that pushes AMTI into the exemption phase-out, where each extra dollar loses part of the exemption: the effective marginal AMT rate becomes 35% in 2025 (28% × 1.25) and 42% in 2026 (28% × 1.5), or 32.5% / 39% in the 26% band.
Frequently asked questions
How is AMT calculated?
Start with regular taxable income, add back AMT adjustments and preferences (the standard deduction or state and local taxes, the ISO bargain element, private activity bond interest and others) to get AMTI. Subtract the exemption, which phases out at higher incomes, then apply 26% and 28% rates to get the tentative minimum tax. AMT is the amount by which the tentative minimum tax exceeds your regular tax.
What is the AMT exemption for 2026?
For 2026 the exemption is $90,100 for single and head of household filers, $140,200 for married filing jointly and $70,100 for married filing separately. It phases out at 50 cents per dollar of AMTI above $500,000 ($1,000,000 joint). For 2025 it was $88,100 / $137,000 with a 25% phase-out above $626,350 / $1,252,700.
Why do incentive stock options trigger AMT?
Exercising ISOs creates no regular income if you hold the shares, but the spread between market value and strike price (the bargain element) is an AMT adjustment. A large exercise can push the tentative minimum tax above regular tax. Selling the shares in the same calendar year removes the adjustment.
What are the AMT tax rates?
26% on the first $244,500 of AMT base in 2026 ($239,100 in 2025) and 28% above it; half those breakpoints for married filing separately. Long-term capital gains and qualified dividends keep their 0%, 15% or 20% rates under AMT.
Can I get AMT back later?
AMT caused by timing items such as the ISO bargain element creates a minimum tax credit. You can use it in later years when your regular tax is higher than your tentative minimum tax, often in the year you sell the ISO shares. Use Form 8801.
How accurate is this AMT estimate?
It follows the Form 6251 structure with the official exemptions and rates, but it simplifies the capital gains part, ignores credits such as the foreign tax credit and assumes your regular tax uses the standard brackets. Use it for planning, then confirm with tax software or a tax professional.
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