How this calculator works
Tax year: 2024, United States. Start from AMTI on Form 6251 or reconcile taxable income with the applicable AMT adjustments. The exemption phases out by 25 cents per dollar over its threshold. Married filing separately also has the special AMTI add-back at high income. This ordinary-income estimate excludes the preferential capital-gain computation and does not decide which credits survive AMT.
Formula
Exemption = max(0, statutory exemption - 25% x excess AMTI). Taxable excess = max(0, AMTI - exemption). Tentative tax applies 26%, then 28%, less AMT foreign tax credit. Additional AMT = max(0, tentative tax - comparable regular tax).
Worked example
A single filer with $200,000 AMTI has an $85,700 exemption, $114,300 taxable excess and $29,718 tentative minimum tax. Against $20,000 comparable regular tax, additional AMT is $9,718.
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Frequently asked questions
Is AGI the same as AMTI?
No. AMTI starts from taxable income and makes Form 6251 adjustments, including certain deductions and preference items.
Does the exemption always apply in full?
No. High AMTI reduces it through a 25% phaseout.
Can I use this with capital gains?
The simplified rates here assume ordinary income. Preferential gains and qualified dividends require Form 6251 Part III.