Stock Options Tax Calculator (ISO vs NSO)
Calculate tax on ISO and NSO stock options at exercise and sale. Compare ISO vs NSO tax treatment.
By Konstantin Iakovlev · Updated April 2026 · Source: IRS — Forms, Instructions & Publications
Spread Per Share
$40.00
Total Spread
$40,000.00
Net After-Tax Value
$34,000.00
Tax Breakdown
| Gross Value | $50,000.00 |
| Total Cost (exercise) | $10,000.00 |
| Total Spread | $40,000.00 |
| AMT at Exercise (28%) | $11,200.00 |
| LTCG Tax at Sale (15%) | $6,000.00 |
| Net After-Tax Value | $34,000.00 |
Use the Stock Options Tax Calculator (ISO vs NSO) above to calculate your results. Enter your values and see instant results — all calculations run in your browser.
Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.
How It Works
Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs) are taxed on very different schedules, and seeing the two side by side helps employees decide how to handle their equity compensation. ISOs can qualify for preferential tax treatment but carry strings attached, whereas NSOs are simply taxed as ordinary income the moment you exercise.
For each option type, the tool works out regular income tax, Alternative Minimum Tax (AMT), and capital gains. Exercising an ISO can pull the spread into AMT, yet that spread escapes regular income tax until you actually sell the shares. An NSO works the opposite way, generating an ordinary income tax bill right at exercise on the gap between the exercise price and fair market value.
One trap worth avoiding is exercising ISOs late in the year without modeling the AMT first, which has a way of producing a tax bill nobody planned for. Note too that ISO advantages disappear in a disqualifying disposition, where shares are sold within two years of grant or one year of exercise. On the brighter side, AMT paid when you exercise ISOs may come back as a credit in later years.
Employee with 1,000 ISOs at $10 strike price, current value $50
- 1 Calculate the spread: 1,000 shares × ($50 current price - $10 exercise price) = $40,000 total spread
- 2 For ISOs: $40,000 spread triggers AMT calculation but no regular income tax. For NSOs: $40,000 is taxed as ordinary income at marginal rate (assume 32% = $12,800)
- 3 ISO AMT impact: $40,000 × 28% AMT rate = $11,200 potential AMT (subject to exemption). NSO also incurs payroll taxes: $40,000 × 7.65% = $3,060 additional
- 4 Total immediate tax cost: ISOs potentially $11,200 (AMT only), NSOs $15,860 ($12,800 income + $3,060 payroll taxes). ISOs provide $4,660 immediate savings but require holding shares for preferential treatment
Source: IRS — Forms, Instructions & Publications · Last updated: April 2026
Frequently Asked Questions
How are stock options taxed?
What is the difference between ISO and NSO tax treatment?
Do I owe AMT on incentive stock options?
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