About the AMT Calculator
This alternative minimum tax (AMT) calculator estimates whether you will owe AMT for 2026 and how much. AMT is a parallel tax system: you add certain deductions and preferences back to your taxable income, subtract a large exemption, apply 26% and 28% rates, and pay whichever is higher — the regular tax or the tentative minimum tax.
The most common AMT trigger today is exercising incentive stock options (ISOs) and holding the shares: the “bargain element” (market value minus strike price) is not regular income but is an AMT preference. Large state and local tax deductions for itemizers and some private-activity bond interest can also push people into AMT. The calculator shows the maximum ISO spread you could add this year before any AMT is due — the figure most startup employees want before exercising.
It uses 2026 figures: exemptions of $90,100 (single) and $140,200 (married filing jointly), phased out at 50 cents per dollar above $500,000 and $1,000,000, and the 28% rate above $244,500 of AMT base. Married filing separately uses a $70,100 exemption and a $122,250 breakpoint. Regular tax is computed with the 2026 ordinary brackets, so the calculator treats all income as ordinary income (no 0%/15%/20% rates on qualified dividends or long-term gains), and it ignores the AMT foreign tax credit and the minimum tax credit carryforward.
With the default inputs, the alternative minimum tax owed is $17,762.00. Change any value above to recalculate instantly.
How to use the amt calculator
- 1Choose your filing status and enter your regular taxable income.
- 2Select whether you took the standard deduction or itemized, and enter SALT if you itemized.
- 3Enter the ISO bargain element for shares you exercised and will still hold at year end.
- 4Add any other AMT adjustments you know about.
- 5Compare the AMT owed with the ISO room figure before deciding how many options to exercise.
Formula and method
Alternative minimum taxable income starts from regular taxable income and adds back items the AMT does not allow: the standard deduction (if you took it), state and local taxes (if you itemized), the bargain element of ISOs exercised and held at year end, and other preference items.
The exemption ($90,100 single or head of household, $140,200 joint, $70,100 separate in 2026) is reduced by 50% of AMTI above $500,000 ($1,000,000 joint). The remaining AMT base is taxed at 26% up to $244,500 ($122,250 separate) and 28% above. If this tentative minimum tax exceeds your regular tax, the difference is AMT. The ISO room figure is found numerically: the extra preference income at which tentative minimum tax exactly equals regular tax.
- AMTI
- Alternative minimum taxable income
- TMT
- Tentative minimum tax
- ISO spread
- (FMV at exercise − strike price) × shares held
Worked examples
Single, $180k taxable income, $100k ISO spread
AMTI is $180,000 + the $16,100 standard deduction + $100,000 ISO spread = $296,100. After the $90,100 exemption, the $206,000 base × 26% gives a tentative minimum tax of $53,560. Regular tax is $35,798, so AMT is $17,762.
Same person, no ISO exercise
Without the ISO exercise, tentative minimum tax is 26% × ($196,100 − $90,100) = $27,560, well below the $35,798 regular tax. Dividing the $8,238 gap by 26% shows about $31,685 of ISO spread could be exercised this year with no AMT.
Married itemizers, $600k taxable, $10k SALT, $300k ISO
At this income the SALT cap has phased down to $10,000, so AMTI is $600,000 + $10,000 + $300,000 = $910,000 — below the $1,000,000 joint phase-out, so the full $140,200 exemption applies. The $769,800 base is taxed at 28% minus $4,890, giving $210,654 of tentative minimum tax versus $147,538.50 of regular tax: $63,115.50 of AMT.
Frequently asked questions
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% of AMTI above $500,000 ($1,000,000 joint).
How do ISOs trigger AMT?+
When you exercise incentive stock options and keep the shares past December 31, the difference between the market value and your strike price counts as AMT income even though it is not regular income, which can create a large AMT bill.
Can I get AMT back later?+
AMT caused by timing items such as ISOs creates a minimum tax credit (Form 8801) that you can use in future years when your regular tax exceeds your tentative minimum tax, including when you sell the shares.
Who typically pays AMT?+
Since 2018 relatively few people pay AMT. It mainly affects people exercising ISOs, high earners who itemize large state and local taxes, and those with private-activity bond interest or large depreciation adjustments.
How can I avoid AMT on ISOs?+
Common strategies are exercising only up to the AMT-free amount each year, exercising early when the spread is small, or exercising and selling in the same calendar year (a disqualifying disposition), which removes the AMT preference.
Tax results are estimates based on published rules and simplified assumptions. They are not tax advice — check official guidance or a tax professional for your situation.