Stock Option Tax Calculator

Estimate taxes on your stock options. Compare ISO vs NSO tax treatment, see the impact of holding periods, and understand AMT exposure.

By NumbersLab Editorial·Updated for 2026 tax year·Editorial standards

Stock options trading screen — representing ISO and NSO stock option tax calculation including AMT implications — Photo by Pawel Czerwinski on Unsplash

Interactive Calculator

All inputs adjust the result in real time. No data leaves your browser.

Tax Year

Grant/Exercise Priceper share

Current/Sale Priceper share

Number of Shares

Option Type

Held Over 1 Year After Exercise?

Filing Status

State

Estimated Tax on Options

$6,00015.0% effective rate

$34,000 after-tax gain from $40,000 total gain

Total Gain

$40,000

1,000 shares × $40 spread

Ordinary Income

None

Capital Gains

$40,000

15% LTCG rate

AMT Exposure

$11,200

Simplified at 28%

Tax Breakdown

Qualifying Disposition

Total Proceeds$50,000

Cost Basis (Exercise Price)−$10,000

Total Gain (Spread)$40,000

Long-Term Capital Gains$40,000

Federal Tax−$6,000

Texas State Tax$0

Total Estimated Tax$6,000

After-Tax Gain$34,000

Potential AMT (if applicable)$11,200

The Background

Incentive Stock Options (ISOs) receive favorable tax treatment if you meet the holding period requirements: you must hold the shares for at least 1 year after exercise and 2 years after the grant date. Meeting both qualifies as a "qualifying disposition" and the entire gain is taxed at the long-term capital gains rate (typically 15%).

If you sell ISO shares before meeting the holding requirements (a "disqualifying disposition"), the spread between exercise price and fair market value at exercise is taxed as ordinary income, similar to NSO treatment.

Non-Qualified Stock Options (NSOs) are simpler: the spread at exercise is always taxed as ordinary income, regardless of how long you hold the shares. Your employer withholds taxes on this amount just like regular wages.

ISOs can trigger the Alternative Minimum Tax (AMT). The spread at exercise is an AMT preference item, meaning you may owe AMT even if you have not sold the shares yet. The simplified AMT estimate shown here uses a 28% rate on the spread — your actual AMT depends on your full tax picture.

Frequently Asked

How are stock options taxed?+

It depends on the option type. Non-Qualified Stock Options (NSOs) are taxed at exercise as ordinary income on the spread (FMV minus strike price). Incentive Stock Options (ISOs) have no regular tax at exercise but the spread is added to Alternative Minimum Tax (AMT) income. For both types, when you eventually sell the underlying shares, the gain from exercise price to sale price is capital gain (short-term if held under 1 year, long-term if over). ISOs that meet the 'qualifying disposition' rules (held 2 years from grant AND 1 year from exercise) get long-term capital gain treatment on the entire spread plus subsequent appreciation.

What is the difference between ISO and NSO?+

ISOs (Incentive Stock Options) are tax-advantaged: no regular tax at exercise, potential for long-term capital gain treatment on the full spread if you meet holding-period requirements. They're limited to $100,000 vesting per year. ISO exercises can trigger Alternative Minimum Tax — the spread is AMT income even though it's not regular income. NSOs (Non-Qualified Stock Options) are simpler but less favorable: spread at exercise is ordinary income with W-2 withholding. NSOs have no AMT issue. ISOs are usually issued to employees only; NSOs can go to employees, consultants, board members, advisors.

What is AMT and how does it affect ISOs?+

Alternative Minimum Tax is a parallel tax system requiring high-income taxpayers to compute tax under two systems (regular and AMT) and pay the higher. ISO exercise adds the spread (FMV minus strike at exercise) to AMT income even though it's not regular income. A large ISO exercise can produce a substantial AMT bill in the year of exercise. Strategies: exercise early in the calendar year (so you can sell shares if value drops before year-end and unwind the AMT), exercise in tranches across multiple years to stay below the AMT exemption ($88,100 single / $137,000 married in 2026), and use AMT Credit in subsequent years to recover the prepaid tax.

When should I exercise my stock options?+

Common strategies: (1) Exercise ISOs early when the spread is small to start the 1-year clock for long-term capital gains while keeping AMT exposure low; (2) Exercise NSOs when you have other deductions or low income to absorb the ordinary income; (3) Cashless exercise (sell-to-cover) if you need cash to pay tax — sell some shares to fund the rest; (4) Time exercises around income — exercise in low-income years (sabbatical, between jobs, before a big bonus year); (5) Avoid exercising right before an IPO if there's high stock price risk; the spread is locked in but the underlying value can drop.

Do I need to pay AMT if I exercise ISOs?+

Not necessarily. The AMT calculation compares your regular tax to your AMT-adjusted tax — you only owe AMT if the AMT calculation exceeds regular tax. For 2026, the AMT exemption is $88,100 single / $137,000 married, with phase-outs starting at $626,350 single / $1,252,700 married. Below those thresholds, modest ISO exercises often don't trigger AMT. Above them, even small ISO spreads can push you into AMT territory. Run the AMT Trigger Calculator on this site before exercising to compute the breakeven point — the maximum spread you can recognize without owing AMT in your situation.