Stock Option Tax Calculator: ISO & NSO After-Tax Value (2026)
Estimate the after-tax value of your stock options at exercise. NSOs are taxed as ordinary income at exercise on the spread (FMV minus strike price) — subject to federal, FICA, and state tax. ISOs have no regular income tax at exercise but may trigger Alternative Minimum Tax (AMT).
On this page: Calculator · NSO vs ISO comparison · How it works · FAQs
Stock option tax calculator
Enter your options, strike price, current fair market value, and estimated tax rate to see exercise cost, taxable income, estimated tax, and after-tax value.
For NSOs: use your total marginal rate (federal + FICA + state). In California at high income, total rate can reach 45–52%. For ISOs: regular tax at exercise = 0%, but AMT may apply — see the reference below. Use your regular rate as a conservative planning estimate for ISOs.
Exercise cost: $
Taxable income (spread): $
Estimated tax: $
After-tax value: $
Effective tax rate: %
NSO vs ISO tax comparison (2026)
Example: 1,000 options, strike $10, FMV $45 at exercise, $35,000 spread. Single filer, $100,000 salary, California resident:
| Scenario | Tax at Exercise | Tax at Sale | Total Tax (est.) | After-Tax Proceeds (est.) |
|---|---|---|---|---|
| NSO — exercise & sell immediately | Ordinary income on $35k (~$14k–$17k at 40–48%) | None (same event) | ~$14,000–$17,000 | ~$18,000–$21,000 |
| NSO — exercise & hold 12+ months | Ordinary income on $35k (~$14k–$17k) | LTCG on appreciation above $45 FMV | Depends on appreciation | Better if stock rises significantly |
| ISO — qualifying disposition (2yr from grant, 1yr from exercise) |
$0 regular tax AMT on $35k spread may apply |
LTCG on full gain ($10 strike to sale price) | ~$5,250 at 15% LTCG (if sold at $45) | ~$29,750 |
| ISO — disqualifying disposition (sold before holding requirements) |
$0 at exercise | Ordinary income on spread at sale | ~$14,000–$17,000 | ~$18,000–$21,000 (same as NSO) |
ISO qualifying disposition is significantly more tax-efficient but requires holding potentially volatile shares for extended periods. AMT on the $35,000 ISO spread in the exercise year could be $7,000–$10,000 depending on total income. Consult a tax professional before exercising large ISO grants.
How stock option taxes work (2026)
NSO (Non-Qualified Stock Options)
At exercise, the spread (FMV minus strike price) is ordinary income, appearing on your W-2. Subject to federal income tax at your marginal rate, FICA (Social Security up to $176,100 + Medicare uncapped at 1.45%), and state income tax. Any appreciation above the FMV at exercise is a capital gain when you sell — long-term if held over 12 months from exercise.
ISO (Incentive Stock Options)
No regular income tax at exercise. The spread is an AMT preference item — it increases Alternative Minimum Tax income and may trigger AMT. To qualify for long-term capital gains treatment at sale, you must hold shares at least 2 years from the grant date AND at least 1 year from the exercise date. Early sale before meeting both requirements is a disqualifying disposition — the spread becomes ordinary income in the year of sale.
Early ISO exercise and 83(b) election
Exercising ISOs early (when the spread is small or zero) starts the 1-year holding clock and minimizes AMT exposure. An 83(b) election filed within 30 days of early exercise of unvested shares locks in the current FMV as the AMT basis. This is a complex decision with significant financial risk — consult a tax professional before acting.
For the full equity compensation picture, see the equity compensation hub or the RSU tax calculator.
Filing taxes with stock options?
NSO exercises and ISO dispositions require careful reporting on Form 3921, Form 6251 (AMT), and Schedule D. These tools handle equity-specific situations:
- TurboTax — handles NSO W-2 income, ISO dispositions, and Form 6251 AMT
- H&R Block — file with a tax professional for large ISO exercises or AMT situations
- FreeTaxUSA — handles W-2 NSO income and Schedule D at low cost
Affiliate links — we may earn a commission at no cost to you.
Related calculators
- RSU tax calculator Estimate tax when RSUs vest — 22% supplemental withholding at vesting
- Capital gains tax calculator Estimate tax when selling stock option shares — short and long-term rates
- Take-home pay calculator See how NSO exercise income stacks with your salary for total W-2 tax planning
- Marginal vs effective tax rate How NSO exercise income pushes combined income into higher brackets
Stock option tax calculator: FAQs
How are NSO stock options taxed?
Non-qualified stock options (NSOs) are taxed as ordinary income at exercise on the spread — the difference between the fair market value and the strike price. This spread is added to your W-2 income and taxed at your marginal federal rate (up to 37%), plus FICA and state income tax. Example: 1,000 NSOs, strike $10, FMV $45 = $35,000 taxable income. At 35% total rate, tax owed = $12,250, leaving $22,750 after tax.
How are ISO stock options taxed?
Incentive stock options (ISOs) are not subject to regular income tax at exercise. However, the spread at exercise (FMV minus strike price) is an AMT preference item and may trigger Alternative Minimum Tax. If you meet the holding requirements — at least 2 years from grant date and 1 year from exercise date — the full gain at sale is taxed as long-term capital gains (0%, 15%, or 20%), not ordinary income. Early sale (disqualifying disposition) results in ordinary income tax on the spread.
What is the difference between ISO and NSO taxes?
NSOs are taxed as ordinary income (up to 37%) at exercise on the spread. ISOs have no regular income tax at exercise but may trigger AMT; with qualifying holding, gains are taxed at long-term capital gains rates (0–20%) at sale. ISOs are generally more tax-advantaged, but AMT risk at exercise and the requirement to hold shares for the qualification period carry real financial risk — especially if the stock price declines after exercise while the AMT bill remains.
Do I owe taxes if I don't sell my stock options after exercising?
For NSOs: yes. Exercising NSOs creates taxable ordinary income equal to the spread, regardless of whether you sell. For ISOs: no regular income tax at exercise, but the spread is an AMT preference item — you may owe AMT even if you hold the shares and they later decline in value. This is the ISO AMT trap: paying tax on paper gains that disappear if the stock price falls before you sell.
Why is my stock option tax so high?
Large NSO exercises generate substantial ordinary income in a single year, stacking on top of your salary and pushing total income into higher marginal brackets (32%, 35%, or 37%). FICA also applies — Social Security up to $176,100 plus Medicare at 1.45% uncapped. In California, state income tax adds another 9–13.3%. Total effective rate on NSO exercises can reach 40–52% in high-tax states. Use the calculator above to estimate your specific situation.
Does this calculator include AMT?
No. This calculator estimates regular income tax at exercise only and does not model Alternative Minimum Tax (AMT). AMT is particularly relevant for ISO exercises in years with large spreads. For ISO AMT analysis, use the calculator in NSO mode (applying your regular rate to the spread as a conservative estimate for planning purposes) and consult a tax professional for the ISO-specific AMT calculation.
Can exercising stock options increase my tax bracket?
Yes. NSO exercise income stacks on top of your salary in the year of exercise, potentially pushing combined income into higher marginal brackets. A $75,000 salary plus $100,000 NSO exercise = $175,000 total income — moving into the 32% bracket. Only income above each threshold is taxed at the higher rate, but large exercises can result in significantly more tax than anticipated. See the marginal vs effective tax rate guide for how bracket stacking works.
Is this calculator tax or financial advice?
No. This tool provides general estimates for informational purposes only and does not constitute tax, legal, or financial advice. Stock option tax situations — particularly ISOs with AMT implications — can be complex. Consult a tax professional before exercising large option grants.