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Stock Option Exercise Tax Calculator

Exercising stock options can create a tax bill with no cash to pay it — the classic ISO AMT trap. Enter your grant, pick ISO or NQSO, and see the bargain element, the estimated 2026 AMT, and what changes if you sell this year or hold for the qualifying holding period.

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What will exercising cost me in tax?

2026 figures per IRS Rev. Proc. 2025-32. This is an educational estimate — it does not reproduce Form 6251. Your other income is used only to place the bargain element in the AMT phaseout.

Option type

ISOs: no regular tax at exercise, but the spread counts for AMT. NQSOs: the spread is ordinary income at exercise.

Shares to exercise

How many options you plan to exercise this year. Spreading exercises across years is the classic AMT defense.

Strike (exercise) price ($/share)

What you pay per share to exercise — from your grant agreement.

Fair market value at exercise ($/share)

The stock's value on exercise day (409A value for private companies). FMV minus strike = the bargain element.

Other income this year ($)

Salary and other AMT income. A big exercise on top of high wages is what wipes out the AMT exemption.

Filing status

Sets your 2026 AMT exemption: $90,100 single · $140,200 joint · $70,100 separate.

Federal marginal tax rate (%)

Your top federal bracket — used for the NQSO ordinary-income estimate. Find it on last year's return or a bracket table.

Regular federal tax, optional ($)

If you know your regular federal tax, enter it to estimate the additional AMT (tentative minimum tax minus regular tax).

Expected sale price ($/share)

What you expect the shares to be worth when you sell — drives the capital-gain side of the math.

Sale plan

Qualifying ISO sales get long-term capital-gain treatment on the whole gain — but you carry the AMT bill meanwhile.

Try:

Estimated tax at exercise$0Enter your numbers to estimate

Enter your numbers above.

How it works: bargain element = shares × (FMV − strike). For ISOs held past year-end, AMT income = your other income + the bargain element; the 2026 exemption ($90,100 single / $140,200 joint / $70,100 separate, Rev. Proc. 2025-32) phases out at 50¢ per $1 over $500k single / $1M joint; tentative minimum tax = 26% of AMT taxable excess to $244,500 ($122,250 if married filing separately), 28% above. Additional AMT = tentative minimum tax minus regular tax. For NQSOs, the spread is ordinary income at exercise (× your marginal rate here; employer withholding and FICA apply on top). Educational estimate only.

How the stock-option tax math works

Two option types, two tax systems. NQSOs are taxed once, simply: the bargain element (market value minus strike at exercise) is ordinary income the year you exercise, and your employer withholds on it. ISOs get a deal under the regular tax system — no tax at exercise — but the alternative minimum tax system adds the bargain element straight to your AMT income. If that pushes your tentative minimum tax above your regular tax, you owe the difference as AMT, in cash, even though you have not sold a single share.

The formula

bargain element = shares × (FMV at exercise − strike) · AMT income = other income + bargain element · exemption_adj = exemption − 0.50 × max(0, AMT income − phaseout) · tentative minimum tax = 26% × excess to $244,500 + 28% × excess above · additional AMT = max(0, tentative minimum tax − regular tax)

Worked example: 2,000 ISOs, $10 strike, $60 FMV

A single filer earning $250,000 exercises 2,000 ISOs at a $10 strike while the stock trades at $60 and holds the shares. Bargain element: 2,000 × ($60 − $10) = $100,000. AMT income: $250,000 + $100,000 = $350,000 — under the $500,000 phaseout, so the full $90,100 exemption survives. AMT taxable excess: $350,000 − $90,100 = $259,900. Tentative minimum tax: 26% × $244,500 + 28% × $15,400 = $63,570 + $4,312 = $67,882. Regular tax is $0 on the exercise itself, so without other income the additional AMT could approach that full figure — owed in cash, with no sale proceeds.

Sell the shares the same year at $70 and the ISO becomes a disqualifying disposition: the $100,000 spread is ordinary income, only the $20,000 of appreciation above $60 is capital gain — but the AMT adjustment vanishes. Hold 1 year past exercise and 2 years past grant and the whole $120,000 gain is long-term capital gain, with the AMT paid now generally recoverable as a credit (Form 8801) in later years.

Output · formula · meaning

Output	Formula	What it means
Bargain element	shares × (FMV − strike)	The “phantom income”: added to AMT income for ISOs, taxed as wages for NQSOs.
Tentative minimum tax	26% to $244,500 + 28% above (2026)	Your tax under AMT rules. Compare it with your regular tax.
Additional AMT	max(0, TMT − regular tax)	What you may actually owe on top of regular tax. Enter your regular tax to see it.
Sale outcome	depends on holding period	Same-year sale = disqualifying (ordinary income on the spread). 1yr+/2yr+ hold = qualifying (long-term gain).

Who uses this

Startup employees with ISOs: model the AMT before exercising — the bill arrives whether or not the company ever IPOs.
Public-company RSU/option holders: compare exercising-and-holding vs exercising-and-selling this year.
Anyone near the phaseout: see how a big exercise wipes out the $90,100/$140,200 exemption at 50¢ per dollar.
Tax-planning in Q4: test splitting an exercise across two tax years to stay under the phaseout threshold.

Accuracy & limitations

Educational estimate, not tax advice and not Form 6251: it does not model capital-gain worksheets, AMT credits (Form 8801) beyond the note above, incentive-stock-option holding-period edge cases, state taxes (some states have their own AMT), or the $100,000 annual ISO exercisability limit (§ 422(d)). 2026 exemption, phaseout, and bracket figures are per IRS Rev. Proc. 2025-32, verified October 2026. Talk to a tax professional before a large exercise — the dollars here are real enough to warrant it.

Comparing equity-heavy offers? The equity vs salary calculator models total compensation; the 1099 vs W-2 calculator covers contractor-vs-employee tax math.

Cite this calculatorBright Side Kit. “Stock Option Exercise Tax Calculator (2026).” brightoolbox.com, 2026.

Bright Side Kit. "Stock Option Exercise Tax Calculator (2026)." https://brightoolbox.com/stock-option-exercise-tax-calculator/ Accessed October 21, 2026.

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Frequently asked questions

Do I owe tax when I exercise incentive stock options?

No regular income tax — but the spread between the stock's value and your strike price is an AMT adjustment. If you hold the shares past year-end and the bargain element is large enough, you can owe AMT in cash with no sale proceeds. Selling in the same calendar year removes the AMT adjustment.

How long do I have to hold ISO shares for the tax break?

More than 1 year after exercise and more than 2 years after the grant date. Sell before either date and it is a disqualifying disposition: the spread at exercise is ordinary income and only the gain above it is capital gain.

What is the AMT exemption for 2026?

Per IRS Rev. Proc. 2025-32: $90,100 single, $140,200 married filing jointly, $70,100 married filing separately. It shrinks by 50¢ per $1 of AMT income over $500,000 (single) or $1,000,000 (joint), and vanishes entirely at $680,200 / $1,280,400.

Can I get AMT paid on an ISO exercise back?

Largely, yes — through the minimum tax credit (Form 8801), which offsets regular tax in later years when your regular tax exceeds your tentative minimum tax. Recovery is slow if the two stay close, and a later year with more ISO exercises can leave nothing to recover.

How are NQSOs taxed at exercise?

The bargain element is ordinary income in the exercise year — your employer withholds federal/state tax and FICA applies. After exercise your basis is the FMV, so only later appreciation is a capital gain (short- or long-term depending on how long you hold).

Should I exercise ISOs all in one year or spread them out?

Spreading exercises across tax years is the classic AMT defense: it keeps each year's bargain element under the exemption and phaseout thresholds. Run both scenarios above — one big exercise vs two half-size ones — and compare the tentative minimum tax.

What happens if the stock falls after I exercise ISOs?

The nightmare scenario: your AMT bill was calculated on the exercise-day value, but your shares are now worth less — you can owe more in AMT than the shares are worth. This is why exercising-and-holding concentrated positions near a peak is dangerous, and why some people sell enough shares to cover the tax.