AMT Calculator
AMT exemption, base, and tentative tax from AMTI and status.
What it does
Alternative minimum tax runs beside regular tax. High earners with big deductions compute both and pay the larger.
The tool above runs Form 6251 math. A single filer at $300,000 AMTI keeps the full $85,700 exemption for a $214,300 base taxed at 26 %, or $55,718.00.
Exemptions phase out with income. Twenty five cents per dollar past thresholds shrinks the shield to zero.
Brackets split at $232,600 of base. Twenty six percent below with twenty eight above minus the offset.
Tentative is not final. Credits and regular tax still decide the actual bill.
How to use
- Pick filing status.
- Enter AMTI.
- Read exemption first.
- Read AMT base next.
- Read tentative tax and see a pro.
Formula
- status
- Filing status setting exemption.
- AMTI
- Alternative minimum taxable income.
2024 Form 6251 figures: single $85,700 over $609,350; joint $133,300 over $1,218,700.
Worked example
Example: single, $300k AMTI
Defaults: single filer with $300,000 AMTI. These are also the default values, so the page opens on this answer.
- Status: single with $300,000 AMTI.
- Exemption: 300000 under 609350, so full $85,700.00.
- Base: 300000 - 85700 = $214,300.00.
- Bracket: 214300 under 232600, so 26 %.
- Tax: 214300 x 0.26 = $55,718.00.
- Tool shows $85,700.00, $214,300.00 AMT base, $55,718.00 tentative AMT.
Reference table
| Status | Exemption | Phaseout at |
|---|---|---|
| Single | $85,700 | $609,350 |
| Joint | $133,300 | $1,218,700 |
| High single | $63,037.50 | $700,000 AMTI |
Limits
- Estimate only, not tax advice.
- 2024 figures used here.
- Credits excluded.
- State AMT excluded.
Common mistakes
- Skipping AMT with big deductions.
- Wrong status thresholds.
- Forgetting phaseout math.
- Ignoring state AMT.
- Filing without pro review.
Try it yourself
Quick checks. Answers sit tucked under each question.
Joint $500k AMTI?
Exemption is full $133,300.00. Base is 500000 - 133300 = $366,700.00. Tax is 366700 x 0.28 - 4652 = $98,024.00.
Single $700k AMTI?
Exemption is 85700 - (700000 - 609350) x 0.25 = $63,037.50. Base is $636,962.50.
Questions
AMT base?
Subtract phased exemption from AMTI. Here 300000 - 85700 = $214,300.00.
Exemption amounts?
Single $85,700, joint $133,300 for 2024, shrinking 25 cents per dollar past thresholds.
AMT brackets?
26 % to $232,600 of base, then 28 % above with a $4,652 offset.
Tentative tax?
Multiply base by 26 %. Here 214300 x 0.26 = $55,718.00.
Final tax owed?
Yes. Credits and regular tax still decide the final bill.
State AMT included?
No. State AMT needs separate math.