ISO vs. NSO Stock Options & AMT Calculator
Select a Startup Equity Scenario or customize below:
Estimated AMT-free exercise capacity
Based on your income, you can exercise up to shares (-- spread) this year with zero Alternative Minimum Tax.
Assumes entered income, standard exemption, and no other preference items.
Exercise & Income Details
For NSOs, states source equity income based on workdays during vesting. The Residence state credits taxes paid to the work state (OSTC).
Immediate Exercise Cash Outlay Check to Write Today
Generates $0.00 in Form 8801 Minimum Tax Credits for future recovery.
Tax establishes full regular basis ($10.00/sh). Zero AMT credit generated.
Visual Tax Analysis
Full Lifecycle Exit & Take-Home Gain (at $30.00 Exit)
What this calculator does
Navigating startup equity can be incredibly complicated, especially when you are trying to understand the differing tax treatments of Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs). This calculator helps you forecast the immediate tax impact and cash requirements when exercising your stock options. By inputting your current salary, option strike price, fair market value (FMV), and the number of shares, the tool estimates your potential Alternative Minimum Tax (AMT) liability for ISOs or ordinary income tax liability for NSOs.
It is designed for tech employees and startup founders who need to decide whether it makes financial sense to exercise their options today. You can model various scenarios to find your estimated AMT-free exercise capacity, allowing you to strategically exercise shares without triggering a massive tax bill. Keep in mind that this tool relies on your inputs and is meant for educational modeling, not as a replacement for professional tax preparation.
How the math works
The calculations follow the statutory mechanisms outlined in IRC §55 and IRS Form 6251. For the 2026 tax year, the Alternative Minimum Tax (AMT) calculation requires adding back the bargain element (the difference between the FMV and your strike price) of your ISOs to your ordinary income to determine your Alternative Minimum Taxable Income (AMTI).
Notably, the recent Omnibus Budget Reconciliation Act (OBBBA) significantly impacted these calculations. Under the OBBBA, the 2026 AMT exemption thresholds were reset to $500,000 for single filers and $1,000,000 for married filing jointly, with the phase-out rate doubling to 50%. This means the exemption is fully exhausted faster at higher income levels, which our engine factors in automatically.
If you hold your ISOs for a qualifying disposition—which strictly requires holding the shares for at least two years from the grant date and one year from the exercise date—your final gains may be taxed at favorable long-term capital gains rates. If you pay AMT upon exercise, you may generate a Minimum Tax Credit (MTC). However, recovery of this credit via Form 8801 depends entirely on your future tax years' ordinary liability exceeding your AMT liability; it is not an immediate refund.
Worked example
Take the High AMT Spread preset above: 15,000 options at a $1.00 strike, a $35.00 current FMV, and $200,000 of ordinary income (single filer, 2026). The bargain element is $34.00 per share, so the total spread is 15,000 × $34 = $510,000, and exercising costs $15,000 in strike price alone.
On the regular side, the $16,100 standard deduction leaves $183,900 taxable, which runs through the 2026 single brackets to $36,734. On the AMT side, AMTI is $200,000 + $510,000 = $710,000. That is $210,000 above the $500,000 OBBBA phase-out threshold, and at the 50% phase-out rate it erases $105,000 of exemption — more than the $90,100 available, so the exemption floors at zero and the full $710,000 is the AMT base. Tentative Minimum Tax is therefore ($244,500 × 26%) + ($465,500 × 28%) = $193,910, and the AMT actually owed is the excess over regular tax: $157,176.
| Step | Arithmetic | Result |
|---|---|---|
| ISO spread | 15,000 × ($35.00 − $1.00) | $510,000 |
| Regular tax | brackets on ($200,000 − $16,100) | $36,734 |
| AMTI | $200,000 + $510,000 | $710,000 |
| Exemption after phase-out | $90,100 − (($710,000 − $500,000) × 50%) | $0 |
| Tentative Minimum Tax | ($244,500 × 26%) + ($465,500 × 28%) | $193,910 |
| Federal AMT owed | $193,910 − $36,734 | $157,176 |
Federal cash needed at exercise is the $15,000 strike plus $157,176 of AMT. Any state AMT (California and Minnesota, for example) is layered on top of this figure by the calculator.
Frequently Asked Questions
Do I owe AMT if I exercise ISOs but don't sell?
What happens if I sell my ISOs in the same year I exercise them?
When do I actually get the Form 8801 AMT credit back?
Should I use an 83(b) election for ISOs?
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Built and verified by The Core-AI Engineering Desk — last reviewed August 31, 2026. Calibrated strictly to 2026 statutory figures.