Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Estimated additional AMT owed
$15,318
ISO bargain element (AMT income added)
$100,000
Tentative minimum tax
$45,318
AMT exemption after phase-out
$85,700
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How to use this
- 1Enter iso shares exercised.
- 2Enter strike price per share ($).
- 3Enter fair market value per share at exercise ($).
- 4Enter regular taxable income (before iso) ($).
- 5Enter estimated regular tax liability ($).
- 6Enter filing status.
- 7Read your estimated additional amt owed on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
Exercising incentive stock options (ISOs) and holding the shares (rather than immediately selling) creates no regular-tax income, but the 'bargain element' — the spread between the exercise price and the fair market value at exercise — counts as income for Alternative Minimum Tax purposes. If that AMT income pushes your AMT liability above what you'd owe under the regular tax system, you pay the difference as AMT, potentially tens of thousands of dollars in cash tax on paper gains you haven't actually sold yet. This calculator estimates your AMT income addition from an ISO exercise, applies the AMT exemption phase-out and 26%/28% AMT rate structure, and compares it against a rough regular-tax estimate so you can see whether — and by how much — the exercise triggers AMT this year.
Worked example
Using the values the calculator loads with:
Inputs
- ISO shares exercised: 5000
- Strike price per share: 4 $
- Fair market value per share at exercise: 24 $
- Regular taxable income (before ISO): 160000 $
- Estimated regular tax liability: 30000 $
- Filing status: Single
Results
- Estimated additional AMT owed: $15,318
- ISO bargain element (AMT income added): $100,000
- Tentative minimum tax: $45,318
- AMT exemption after phase-out: $85,700
What each field means
Inputs
- ISO shares exercised
- The iso shares exercised used in the calculation. Starts at 5000 so you have a working example on load.
- Strike price per share ($)
- The strike price per share used in the calculation, measured in $. Starts at 4 $ so you have a working example on load.
- Fair market value per share at exercise ($)
- The fair market value per share at exercise used in the calculation, measured in $. Starts at 24 $ so you have a working example on load.
- Regular taxable income (before ISO) ($)
- The regular taxable income (before iso) used in the calculation, measured in $. Starts at 160000 $ so you have a working example on load.
- Estimated regular tax liability ($)
- The estimated regular tax liability used in the calculation, measured in $. Starts at 30000 $ so you have a working example on load.
- Filing status
- Pick the option that matches your situation — the maths changes per option. Choices: Single, Married filing jointly.
Results
- Estimated additional AMT owed
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- ISO bargain element (AMT income added)
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Tentative minimum tax
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- AMT exemption after phase-out
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Can I get the AMT I paid back later?
Often yes, through the AMT credit. If you pay AMT in the exercise year because of the ISO bargain element, and in a later year your regular tax exceeds your tentative minimum tax, you can claim a credit against that excess, effectively recovering some or all of the AMT paid over time — though it may take several years.
How do I avoid a big AMT surprise?
Exercise ISOs gradually across multiple years rather than all at once, model the AMT impact before December 31 (since AMT is calculated on the calendar year), and consider exercising early in a year when the stock price is low relative to what you expect later, since AMT is based on the spread at exercise, not at sale.
What if I exercise and sell in the same calendar year?
A 'disqualifying disposition' in the same year generally removes the AMT preference item — the sale converts the ISO into ordinary income treatment for regular tax, which usually eliminates the separate AMT problem, though you lose the potential long-term capital gains treatment on the gain.
Does this calculator give an exact AMT number?
No — it's a simplified estimate covering the core mechanics (exemption phase-out, 26%/28% rate brackets). Real AMT calculations include other preference items (state tax addback, certain deductions) via Form 6251. Use this to gauge magnitude, then confirm with a tax professional before exercising a large ISO grant.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
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Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). AMT on ISO Exercise Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/amt-iso-exercise
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/amt-iso-exercise" target="_blank" rel="noopener">AMT on ISO Exercise Calculator — RevenueLab</a> (2026).</p>
Source: [AMT on ISO Exercise Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/amt-iso-exercise) (2026).