Alternative Minimum Tax Calculator

Use this calculator to estimate whether the alternative minimum tax (AMT) will be higher than your regular federal income tax for 2026 or 2025. Enter your filing status, regular taxable income, any long-term gains and qualified dividends, whether you itemize, and your AMT adjustments and preferences; the tool works out your regular tax, exemption, tentative minimum tax, and any AMT due.

Short answer: for 2026 you owe AMT only if your tentative minimum tax is higher than your regular tax. Tentative minimum tax is 26% of alternative minimum taxable income (AMTI) after an exemption of $90,100 (single or head of household) or $140,200 (married filing jointly), and 28% on the excess above $244,500. The exemption shrinks by 50 cents for every dollar of AMTI over $500,000 (single) or $1,000,000 (joint), per Rev. Proc. 2025-32.

This calculator is for informational purposes only. Its results are estimates, not a completed Form 6251, and they may differ from what tax software or the IRS computes.

What are the 2026 AMT exemption and phaseout amounts?

The 2026 figures come from section 4.10 of Rev. Proc. 2025-32. The 2027 figures come from section 3.11 of Rev. Proc. 2026-35, published November 5, 2026; the calculator offers 2027 in the Tax Year menu. The 2025 figures come from Rev. Proc. 2024-40 and match the 2025 Form 6251 instructions.

The endpoints show the new 50% rate. A single filer's $90,100 exemption disappears after $180,200 of AMTI above $500,000 ($500,000 + 2 × $90,100 = $680,200). The 2025 single exemption took $352,400 of excess AMTI to disappear at 25% ($626,350 + 4 × $88,100 = $978,750).

Public Law 119-21, section 70107 made the higher TCJA exemptions permanent but reset the phaseout thresholds to $500,000 and $1,000,000 and raised the phaseout rate from 25% to 50%. The thresholds are indexed again from 2027, when they reach $515,950 and $1,031,900.

A child subject to the kiddie tax gets an AMT exemption no larger than earned income plus $9,750 for 2026 ($10,050 for 2027, Rev. Proc. 2026-35 section 3.12).

How does the AMT calculation work?

The AMT is a second, parallel tax computation. You figure regular tax the normal way, then refigure income under AMT rules on Form 6251:

1. Start with taxable income. For 2025 and later, Form 6251 lines 1a and 1b produce your taxable income with the new $6,000 senior deduction added back. The IRS treats that deduction as a personal exemption, which AMT does not allow. The tips, overtime, and car-loan interest deductions are not added back.
2. Add back the standard deduction or your itemized taxes. If you take the standard deduction, line 2a adds it back. If you itemize, line 2a adds back your state and local taxes from Schedule A line 7 instead.
3. Add other adjustments and preferences. The common ones are the ISO bargain element (line 2i), interest on specified private activity bonds (line 2g), depreciation differences, and passive activity differences.
4. Subtract the exemption, reduced by 50% of AMTI above the phaseout threshold.
5. Apply the AMT rates. 26% on the first $244,500 of the remaining amount and 28% above it. A shortcut for the 28% zone: multiply by 28% and subtract $4,890 (2% × $244,500), or $2,445 if married filing separately.
6. Compare. The result is tentative minimum tax. AMT is the amount by which it exceeds your regular tax. You pay regular tax plus AMT, which equals the larger of the two numbers.

Long-term capital gains and qualified dividends are carved out in Form 6251 Part III and taxed at 0%, 15%, or 20%, just as under the regular tax.

What do the calculator inputs mean?

What the result shows: AMTI and each piece that built it, the exemption after the phaseout, the taxable excess, tentative minimum tax, regular tax, and AMT. If AMT is zero, the tool shows your cushion — how far regular tax sits above tentative minimum tax — instead of a "subject to AMT" warning.

What it leaves out: the AMT foreign tax credit, the minimum tax credit from earlier years, unrecaptured section 1250 gain, and AMT-versus-regular basis differences when you sell ISO shares or depreciated property.

Worked example: an ISO exercise that triggers AMT

A single filer earns $420,000 in wages in 2026 and itemizes $40,400 of state and local taxes (the full SALT cap, since MAGI is under $505,000) plus $20,000 of mortgage interest. She exercises incentive stock options with a $250,000 spread and holds the shares into 2027.

Regular tax:

• Taxable income: $420,000 − $60,400 = $359,600
• Tax: $58,448 + 35% × ($359,600 − $256,225) = $58,448 + $36,181 = $94,629

The ISO spread does not show up in regular taxable income when you hold the shares.

AMT:

• AMTI: $359,600 + $40,400 SALT add-back + $250,000 ISO spread = $650,000
• Exemption phaseout: ($650,000 − $500,000) × 50% = $75,000
• Remaining exemption: $90,100 − $75,000 = $15,100
• Taxable excess: $650,000 − $15,100 = $634,900
• Tentative minimum tax: 26% × $244,500 + 28% × $390,400 = $63,570 + $109,312 = $172,882
• AMT: $172,882 − $94,629 = $78,253

To reproduce this in the calculator, choose 2026, Single, $359,600 taxable income, itemized deductions, $290,400 of adjustments ($40,400 SALT + $250,000 ISO spread), and leave regular tax blank; it shows $94,629 of regular tax, a $15,100 exemption, $172,882 of tentative minimum tax, and $78,253 of AMT.

If $100,000 of her taxable income were long-term gains instead of wages, regular tax would drop to $74,629, and tentative minimum tax to $159,882 because the gains keep their 15% rate under Part III — AMT would be $85,253. Gains don't escape AMT; they just aren't taxed at 26% or 28%.

Without the ISO exercise, AMTI would be $400,000. That is under the threshold, so she keeps the full $90,100 exemption. Tentative minimum tax would be $63,570 + 28% × ($309,900 − $244,500) = $81,882, below her $94,629 of regular tax, so she would owe no AMT. The exercise alone added $78,253 of tax in a year when she may not have sold a single share. Model exercise sizes on the ISO tax calculator before you buy and hold.

How close are high-SALT itemizers to AMT?

Closer than most people think. A married couple has $480,000 of AGI and itemizes $40,400 of SALT, $30,000 of mortgage interest, and $7,600 of charitable gifts (after the new 0.5%-of-AGI floor), for $78,000 total.

• Regular taxable income: $480,000 − $78,000 = $402,000
• Regular tax: $35,932 + 24% × ($402,000 − $211,400) = $35,932 + $45,744 = $81,676
• AMTI: $402,000 + $40,400 = $442,400 (full $140,200 exemption)
• Taxable excess: $442,400 − $140,200 = $302,200
• Tentative minimum tax: $63,570 + 28% × $57,700 = $63,570 + $16,156 = $79,726

They owe no AMT, but the cushion is only $1,950 — the figure the calculator shows for married filing jointly, $402,000 of taxable income, itemized, and $40,400 of adjustments. Adding $10,000 of private activity bond interest would raise tentative minimum tax by $2,800 and create about $850 of AMT. Because the SALT cap rose to $40,400 in 2026, the add-back is bigger than it was under the $10,000 cap, which narrows that cushion for itemizers in high-tax states.

Why the phaseout zone has a 39% or 42% marginal rate

Inside the phaseout range, each extra dollar of AMTI raises the taxable excess by $1.50: the dollar itself plus 50 cents of lost exemption. At the 28% rate that works out to 1.5 × 28% = 42% on each additional dollar. If you are still in the 26% band, it's 1.5 × 26% = 39%. For a single filer, that zone runs from $500,000 to $680,200 of AMTI. For joint filers, it runs from $1,000,000 to $1,280,400.

Under 2025 law the same zone added only 25 cents per dollar, a marginal rate of 35%. This is why a bonus, a Roth conversion, or a large gain can cost more than your bracket suggests in a year when you are already near the AMT threshold.

What triggers AMT most often?

Most of these come straight from the line-by-line instructions. The Form 6251 instructions also note that private activity bonds issued in 2009 or 2010 are generally exempt from the preference. Mortgage interest on acquisition debt and charitable contributions are not added back, so they still reduce AMTI.

One counterintuitive tip from the same instructions: if you owe AMT, itemizing can lower your total tax even when your itemized deductions are smaller than the standard deduction. The standard deduction is worth nothing for AMT, while mortgage interest and charity are.

Does AMT tax capital gains at 28%?

No. Form 6251 Part III reproduces the qualified dividends and capital gain worksheet, so long-term gains and qualified dividends are still taxed at 0%, 15%, or 20% in tentative minimum tax. A large gain hurts in a different way. It inflates AMTI, eats the exemption in the phaseout zone, and leaves more of your ordinary income exposed to the 26% and 28% rates.

The 3.8% net investment income tax is separate from AMT and applies on top of either system. Check it on the NIIT calculator, and use the capital gains calculator for the regular-tax side of a sale.

How does the minimum tax credit work?

AMT you pay because of deferral items, like the ISO spread or depreciation timing, becomes a minimum tax credit that carries forward on Form 8801. You can use it in any later year when your regular tax exceeds your tentative minimum tax. AMT caused by exclusion items never comes back. Those are the standard deduction, itemized taxes, and tax-exempt private activity bond interest.

In the ISO example above, nearly all of the $78,253 is a deferral-item credit. When she sells the shares in a later year, her AMT basis includes the $250,000 she already reported, so the AMT gain is smaller than the regular-tax gain. That gap is what lets regular tax rise above tentative minimum tax and free up the credit. Track two basis numbers for every ISO lot: regular basis (the strike price) and AMT basis (strike price plus the spread you reported).

Common mistakes when estimating AMT

• Entering salary instead of taxable income. The first input is post-deduction taxable income, not gross pay.
• Adding the standard deduction twice. If you choose "Standard deduction," the tool adds it back for you ($16,100 single or $32,200 joint for 2026). Put only the senior deduction and other items in adjustments.
• Adding back all itemized deductions. Only state and local taxes come back. Mortgage interest on acquisition debt and charitable gifts stay deductible for AMT.
• Including ISO shares sold in the same year. If you exercise and sell in the same calendar year, the regular tax and AMT treatment match and there is no line 2i adjustment.
• Comparing against tax after credits. Compare tentative minimum tax with regular tax before credits.
• Assuming the old thresholds. Anyone who ran AMT for 2025 at $626,350 or $1,252,700 needs to rerun 2026 at $500,000 or $1,000,000.

How to use the result

If the tool shows $0 AMT owed, compare the gap between your regular tax and tentative minimum tax. A thin gap means one more ISO exercise or a private-activity muni fund could tip you over. If it shows AMT, you have three levers:

1. Spread ISO exercises across years so each year's spread stays below the point where tentative minimum tax overtakes regular tax.
2. Exercise early in the year. A January exercise leaves time to sell before December 31 (a disqualifying disposition that removes the AMT adjustment) if the stock falls.
3. Avoid stacking income events. Keep a Roth conversion out of a heavy ISO year, especially inside the 42% phaseout zone.

AMT is not built into payroll withholding. If the estimate shows AMT, cover it with extra withholding on the tax withholding calculator or with quarterly payments as described in how to pay quarterly estimated taxes. For the rest of the 2026 parameter set, see the IRS inflation adjustments guide and the OBBBA tax changes guide. The itemized deduction limit for the 37% bracket is another 2026 rule that affects the same high-income itemizers.