AMT Calculator

Estimate your Alternative Minimum Tax: calculate AMTI, apply the phased-out exemption, and compare the Tentative Minimum Tax to your regular federal tax liability.

Quick Facts

Formula
TMT = 26%/28% × (AMTI − exemption)
AMT owed = max(0, TMT − regular tax). Rates use 2025 IRS thresholds.
2025 exemption
$88,100 single/HOH · $137,000 MFJ
Phases out 25 cents per dollar of AMTI above the threshold.
Rate breakpoint
$239,100 ($119,550 if MFS)
26% below the breakpoint, 28% on the AMT base above it.

Your Results

Calculated
AMTI
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Alternative Minimum Taxable Income
AMT exemption
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After phase-out for your filing status
Tentative minimum tax
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26%/28% applied to the AMT base
AMT owed
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Extra tax beyond your regular liability

Ready

Enter your filing status, taxable income, AMT addbacks, and regular tax, then press Calculate.

How the AMT Calculator works

The Alternative Minimum Tax is a parallel tax system that recalculates your liability after adding back deductions and preference items the regular tax code allows but the AMT does not. You pay whichever is higher: your regular tax or the AMT. This calculator runs the standard IRS method — build Alternative Minimum Taxable Income (AMTI), subtract your phased-out exemption, apply the two-tier 26%/28% rate, and compare the result to your regular tax.

The formula

Step by step, using 2025 tax year figures:

  • AMTI = Regular taxable income + AMT addbacks. Common addbacks include the state and local tax (SALT) deduction, the bargain-element spread on exercised incentive stock options (ISOs), certain miscellaneous itemized deductions, and private-activity bond interest.
  • Exemption = Base exemption − 25% × max(0, AMTI − phase-out threshold). For 2025 the base exemption is $88,100 (single/HOH), $137,000 (married filing jointly), or $68,500 (married filing separately), phasing out at $626,350 of AMTI ($1,252,700 for joint filers).
  • AMT base = max(0, AMTI − exemption).
  • Tentative Minimum Tax (TMT) = 26% × AMT base up to $239,100 ($119,550 MFS), plus 28% × the amount above that breakpoint.
  • AMT owed = max(0, TMT − regular federal tax). You only pay the difference — the AMT is not stacked on top of your regular tax dollar for dollar.

Worked example

A single filer with $350,000 of regular taxable income and $40,000 of AMT addbacks (a large SALT deduction plus an ISO exercise spread) has AMTI of $390,000. That is below the $626,350 phase-out threshold, so the full $88,100 exemption applies, leaving an AMT base of $301,900. Tax on that base is $239,100 × 26% + $62,800 × 28% = $62,166 + $17,584 = $79,750 of Tentative Minimum Tax. If their regular federal tax liability is $65,000, they owe an extra $14,750 in AMT.

What triggers AMT liability

  • Large SALT deductions: the state and local tax deduction is fully disallowed for AMT purposes, which is the single most common trigger for taxpayers in high-tax states.
  • Incentive stock option exercises: exercising ISOs and holding the shares creates an AMT preference equal to the spread between the exercise price and fair market value, even though no regular-tax income is recognized until sale.
  • High income with few AMT-disallowed deductions: as regular taxable income rises, the AMT exemption phases out, narrowing the gap between the two systems.

When to re-run this calculation

Re-run the estimate whenever your income mix changes — a new ISO exercise, a jump in state taxes paid, a large capital gain, or a shift in filing status. The AMT exemption and breakpoint amounts are adjusted for inflation each year, so figures should be updated when the IRS releases new thresholds.

Frequently Asked Questions

How is Alternative Minimum Tax calculated?
Start with your regular taxable income and add back AMT preference and adjustment items (such as the state and local tax deduction and the ISO exercise spread) to get Alternative Minimum Taxable Income (AMTI). Subtract your AMT exemption, which phases out 25 cents per dollar of AMTI above a threshold, to get the AMT base. Apply 26% to the AMT base up to the year's rate breakpoint and 28% above it to get the Tentative Minimum Tax (TMT). AMT owed equals TMT minus your regular federal tax, floored at zero.
What are the 2025 AMT exemption and phase-out amounts?
For the 2025 tax year, the AMT exemption is $88,100 for single and head of household filers, $137,000 for married filing jointly, and $68,500 for married filing separately. Exemptions begin phasing out at $626,350 of AMTI for single, head of household, and married filing separately filers, and at $1,252,700 for married filing jointly, reduced 25 cents for every dollar of AMTI above the threshold until fully phased out.
What is the 26%/28% AMT rate breakpoint?
For 2025, the Tentative Minimum Tax rate is 26% on the first $239,100 of the AMT base ($119,550 if married filing separately) and 28% on the amount above that threshold. This two-tier rate structure is flatter than the regular seven-bracket income tax, which is why high earners with large addback items can end up owing more under AMT.
Do I actually owe the AMT amount shown here?
You owe AMT only when the Tentative Minimum Tax exceeds your regular federal tax liability, and the extra amount is the difference between the two. If TMT is lower than your regular tax, you owe no additional AMT. This calculator performs the standard comparison but does not replace Form 6251 or a tax professional's review of your specific preference items.

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