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Form 6251 Calculator

Estimate alternative minimum tax on Form 6251 for 2026, including the effect of exercising incentive stock options.

Updated November 4, 2026. Free, no sign-up; everything runs in your browser and nothing you type is stored.

Form 6251 AMT calculator (2026)

Filing statusRegular taxable income ($)Do you itemize?If itemizing: state and local taxes deducted ($)ISO bargain element: (FMV − strike) × shares ($)Other AMT adjustments ($)

Alternative minimum tax (Form 6251)

–

–AMT income (AMTI)

–Exemption after phase-out

–Tentative minimum tax

–Regular tax (ordinary rates)

–Room before AMT

How Form 6251 works

The alternative minimum tax is a second tax calculation with fewer deductions. You figure it on Form 6251 and pay whichever is higher, regular tax or tentative minimum tax. The 2026 amounts (Rev. Proc. 2025-32, after the 2025 tax law):

Exemption: $90,100 single or head of household, $140,200 joint, $70,100 married filing separately.
Phase-out: the exemption drops by 50 cents for each dollar of AMT income over $500,000 ($1,000,000 joint), gone at $680,200 ($1,280,400 joint). The phase-out rate doubled from 25% starting in 2026.
Rates: 26% on the first $244,500 of income over the exemption ($122,250 MFS) and 28% above that.

What gets added back

The standard deduction, or state and local taxes if you itemize.
The bargain element of incentive stock options exercised and held past year-end: fair market value minus strike price, times shares. This is the most common AMT trigger.
Private activity bond interest and some depreciation differences.

Worked example

A single filer with $150,000 of taxable income (standard deduction) exercises ISOs with a $100,000 spread. AMT income is $266,100; the full $90,100 exemption applies, leaving $176,000 taxed at 26% = $45,760. Regular tax is $28,598, so Form 6251 adds $17,162 of AMT. That AMT on ISOs usually becomes a credit (Form 8801) in later years. Plan exercises with the ISO exercise guide; long-term gains keep 0/15/20% rates under AMT, which this estimate doesn't model.

Common questions

What is the 2026 AMT exemption?

$90,100 single, $140,200 joint, $70,100 married filing separately.

When does the AMT exemption phase out in 2026?

Above $500,000 of AMT income ($1,000,000 joint), at 50 cents per dollar.

Do ISOs trigger AMT?

The bargain element of ISOs exercised and held is added to AMT income.

What are the AMT rates?

26% on the first $244,500 over the exemption, 28% above.

Sources

More paycheck and tax calculators: Form 4868 Calculator · Form 5329 Calculator · Form 706 Calculator · Form 8606 Calculator

General information, not financial, tax or legal advice. Check important numbers with the official source before acting on them.