Stock Option Calculator
This stock option calculator estimates what your equity grant is really worth — turning your strike price, current share price, vesting schedule, and tax rate into clear pre-tax and after-tax profit figures. It is built for startup employees and founders who want to understand a grant before exercising.
Stock options give you the right to buy company shares at a fixed strike price. The gap between the current share price and your strike price is the spread — the intrinsic value of each option. The calculator multiplies that spread across your granted options, subtracts your exercise cost and estimated tax, and shows the result instantly as you type.
How to Use the Stock Option Calculator
Enter your option details
Type your Total Options Granted, pick the Option Type (ISO or NSO), and enter your Strike Price and Current Share Price (fair market value or expected exit price).
Set vesting and tax
Choose your Vesting Period (typically 4 years) and Cliff Period (typically 1 year). The Tax Rate defaults to 15% for ISO and 35% for NSO — adjust it to match your situation.
Review your results
See Pre-tax Profit, Spread / Option, Exercise Cost, and After-Tax Profit update in real time. If your strike is above the share price, the result is flagged as Underwater.
Explore scenarios
Check the Exit Scenarios to compare your value at 0.5×, 1×, 2×, 5×, and 10× the current price, and expand the Vesting Schedule for a year-by-year breakdown.
Features
Full Profit Breakdown
Calculates option spread, exercise cost, and both pre-tax and after-tax profit from a single set of inputs.
ISO vs NSO Toggle
Switch between ISO and NSO to see how each tax treatment changes your bottom line — the rate defaults to 15% or 35% automatically.
Vesting Schedule
A year-by-year vesting table that handles the cliff correctly — nothing before the cliff, then the accumulated amount vesting at once.
Exit Scenario Analysis
Five valuations from pessimistic (0.5×) to best case (10×), each showing the exit price, pre-tax profit, and after-tax profit.
Underwater Detection
When your strike price exceeds the share price, options are flagged underwater with a clear badge and color change.
Multi-Currency Support
Pick your currency and every input, result, and scenario updates to the matching symbol.
Real-Time Calculation
Every result updates instantly as you type — there is no calculate button to press.
Frequently Asked Questions
How do you calculate the value of a stock option?
Subtract your strike price from the current share price to get the spread per option, then multiply by the number of options to get the pre-tax value. This calculator also subtracts your exercise cost (strike price × options) and an estimated tax to show your after-tax profit.
What is the difference between ISO and NSO?
ISO (Incentive Stock Options) can qualify for long-term capital gains rates if you meet the holding requirements (1 year from exercise and 2 years from grant), though the spread at exercise may trigger Alternative Minimum Tax. NSO (Non-Qualified Stock Options) are taxed as ordinary income on the spread at exercise. The calculator defaults to 15% for ISO and 35% for NSO, and you can adjust the rate.
What does "underwater" or "in the money" mean?
Options are underwater when the current share price is at or below your strike price — exercising would cost more than the shares are worth, so the intrinsic value is zero. They are in the money when the share price is above your strike, giving a positive spread. Underwater options can still gain value if the share price rises before they expire.
How does the cliff period work?
A cliff is the initial waiting time before any options vest. With a 4-year schedule and a 1-year cliff, nothing vests in the first year; at the 1-year mark the accumulated portion vests at once, then the rest vests on a regular schedule. The Vesting Schedule table flags the cliff year so you can see exactly when your options start unlocking.
How much does it cost to exercise stock options?
The exercise cost is your strike price multiplied by the number of options you exercise — it is the cash you pay to buy the shares, separate from any tax. The calculator shows this as Exercise Cost so you can budget for it alongside your expected profit.
What tax rate should I use?
The calculator defaults to 15% for ISO (long-term capital gains) and 35% for NSO (ordinary income), but your real rate depends on your total income, filing status, state taxes, and whether you meet holding requirements. Treat the result as an estimate and consult a tax advisor for personalized guidance.
How accurate are the exit scenarios?
Exit scenarios apply simple multiples (0.5× to 10×) to the current share price to show potential value at different valuations. They are estimates for fully vested options and do not account for dilution from future funding rounds, liquidation preferences, or market conditions at exit. For a full picture, pair this with a cap table tool.
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