How it works

The math, with nothing hidden

Every number the calculator shows comes from the steps below. When we don't know something, we use a typical value, label it as a guess, and show you how much it matters.

1. What you own

Your ownership is your shares divided by the company's fully diluted share count: every share that exists or could, including the unused option pool. If you don't know the count, we work it out from the last valuation and the price investors paid per share, or from the ownership % in your offer letter. If none of those are known, we use a typical count for the company's stage and warn you.

2. Future funding rounds

Each new round issues new shares, so everyone's slice gets smaller. We use the median dilution of recent rounds at each stage, plus a small option-pool top-up, and a typical number of rounds left: three from seed or Series A, two from Series B, one from Series C, none after that. Later rounds dilute less, so the average shrinks as a company matures. You can change both. We update the fundraising benchmarks behind these defaults (valuations and dilution by stage) every quarter from publicly available sources, including Carta and NVCA, among others. The current set covers Q3 2025–Q2 2026.

3. Investors get paid first

Investors usually hold preferred stock with a 1× liquidation preference: in a sale, they can take their money back before common shareholders get anything, or convert to common and share pro rata, whichever pays them more. We estimate what they're owed as the last valuation times their typical ownership for the stage.

This is why small sales often pay employees little or nothing, and it's the flat stretch at the start of the chart. Many calculators skip this step, which makes small exits look far better than they are.

4. What each share gets

After preferences, whatever is left is split across common shares. For options, your payout is that price minus your strike, times your shares. RSUs have no strike.

5. Cost to exercise and tax

• Exercise cost is your strike times the shares you exercise.
• ISOs exercised early may owe alternative minimum tax on the gap between today's 409A and the strike (we use 26%, then 28% on larger amounts). Selling after the holding period is taxed as long-term capital gains.
• NSOs owe income tax on that gap when you exercise, then capital gains on any growth.
• Exercising when the company sells means no cash up front, but the whole gain is taxed as income.
• RSUs are taxed as income when the shares are delivered, usually at the sale for private companies.
• State tax uses a flat top rate for your state if you choose one.

These are deliberately simple, flat-rate estimates. We don't model the AMT credit, the $100K ISO limit, city taxes, or your other income, and we say so next to the numbers they affect.

6. Break-even

The break-even is the lowest sale price at which what you take home, after exercise cost and estimated tax, turns positive.

How we check it

The engine is plain, dependency-free code with automated tests at 100% line coverage, checked against worked examples calculated by hand for ISOs, NSOs, and RSUs.

Spot something wrong? Tell us. We'd rather be corrected than confidently wrong. Or try it with your own numbers.

Educational purposes only. Not financial, tax, or legal advice.