Stock Option Calculator Startup
What an option grant is worth at several exit valuations — vesting, strike, exercise cost, and the dilution that most equity calculators leave out. Because the percentage on your grant letter is not the percentage you will own at an exit.
Free · No signup · Runs entirely in your browser
What a grant is actually worth, at several exit valuations. This startup stock option calculator applies expected dilution to the result — future rounds issue new shares, so the percentage on your grant letter is not the percentage you will own at an exit.
The number on your grant letter.
What you pay per share to exercise.
Fully diluted. Ask; you are entitled to know.
The last round’s post-money.
In years. Four is standard.
Months before anything vests at all.
How long you have been there.
Rounds between now and an exit will shrink your share.
| Exit | Valuation | Price/share | Net on full grant | After dilution |
|---|---|---|---|---|
| 1× | $50.0M | $5.00 | $40,000 | $28,000 |
| 2× | $100.0M | $10.00 | $90,000 | $63,000 |
| 5× | $250.0M | $25.00 | $240,000 | $168,000 |
| 10× | $500.0M | $50.00 | $490,000 | $343,000 |
The last column is the one worth reading. At a 10× exit the grant looks like $490,000 before dilution and $343,000 after — and dilution is the assumption most equity calculators leave out entirely.
Two more things this cannot model. Liquidation preferences pay investors before common stock, so at a low exit the numbers above can all be zero regardless of what the arithmetic says. And exercising can trigger tax before you have sold anything — in the US, the spread on an ISO exercise counts toward AMT. Both are worth an hour with someone qualified before you write a cheque.
An option grant is a bet on the company shipping. If you are building the product largely on your own, Tekk turns what you want into specs your coding agent can actually execute.
The calculation
price per share = valuation ÷ total shares outstanding
net value = options × (exit price per share − strike price)
The number that does the work is total shares outstanding, and it is the one grant letters most often omit. Ten thousand options is meaningless on its own — in a company with 1 million shares it is 1%, and in one with 100 million it is 0.01%. If you have not been told, ask.
Worked example
A 10,000-option grant at a $1 strike, in a company with 10 million shares valued at $50m. Eighteen months into a four-year vest with a one-year cliff.
| Price per share today | $5.00 |
| Your share of the company | 0.100% |
| Vested so far | 3,750 options (37.5%) |
| Cost to exercise those | $3,750 |
| Worth today, net of strike | $15,000 |
Exit scenarios
On the full 10,000-option grant, with 30% expected further dilution:
| Exit | Valuation | Price/share | Net | After dilution |
|---|---|---|---|---|
| 1× | $50m | $5 | $40,000 | $28,000 |
| 2× | $100m | $10 | $90,000 | $63,000 |
| 5× | $250m | $25 | $240,000 | $168,000 |
| 10× | $500m | $50 | $490,000 | $343,000 |
The last column is the point of the page. A 10× exit looks like $490,000 and is realistically $343,000 — and dilution is the assumption almost every equity calculator omits, because leaving it out makes the number bigger.
Why dilution is not optional
Every priced round issues new shares. Existing holders are not losing shares; the denominator is growing underneath them. A typical round dilutes by 15–25%, option pool top-ups add more, and two rounds before an exit lands somewhere around 30–40% in total.
Nobody takes anything from you. Your slice simply becomes a slice of a larger pie, and the hope is that the pie grows faster than your slice shrinks — which is the entire bet.
Three things this cannot tell you
Liquidation preferences. Investors are paid before common stock. A company that raised $80m and sells for $100m may owe the first $80m to preferred holders, leaving $20m to split among everyone else. At a low enough exit, common stock is worth nothing regardless of what the table above says.
Tax on exercise. In the US, exercising an incentive stock option can create alternative minimum tax on the spread — tax owed on a gain you have not received in cash and may never realise. People have gone bankrupt this way.
The 90-day window. Leave, and you typically have 90 days to exercise or forfeit. That turns a paper asset into a cash decision at the worst possible moment. Some companies now offer extended windows; it is worth asking before you need to know rather than after.
How it works
- 1
Enter what the grant letter says
Options granted, strike price, and — the one you may have to ask for — total shares outstanding on a fully diluted basis. Without that last number a grant of 10,000 options means nothing, because it could be 1% of the company or 0.001%.
- 2
Add your vesting position
Four years with a one-year cliff is standard. This stock option calculator startup employees can actually use shows what has vested, what it would cost to exercise it, and what it is worth at today's valuation net of the strike.
- 3
Read the after-dilution column
Exit values are shown at 1×, 2×, 5× and 10× today's valuation, with and without expected dilution. The second figure is the honest one: every round between now and an exit issues new shares, and your slice gets thinner without anyone taking anything from you.
Frequently asked questions
- How do I work out what my stock options are worth?
- A stock option calculator startup employees can trust multiplies the options by the exit price per share, then subtracts the strike price on every share you exercise. The exit price per share is the exit valuation divided by total shares outstanding — which is why that share count matters more than any other number on your grant letter.
- What is a strike price?
- What you pay per share to convert an option into actual stock. It is set at the fair market value when the option was granted, so an early employee typically has a low strike and a late one a high strike on the same company. Your gain is the difference between the strike and what the share is eventually worth.
- Why does a startup stock option value calculator need to model dilution?
- Because it applies to every future round and compounds. A grant that is 0.10% of the company today becomes roughly 0.07% after 30% of further dilution — so at a $500m exit, the difference between the naive figure and the real one is hundreds of thousands of dollars. Most equity tools, and every startup stock option value calculator we found on this search, simply do not model it.
- How much dilution should I assume?
- It depends how many rounds are left. A typical priced round dilutes existing holders by 15–25%, and option pool top-ups add more. Two more rounds before an exit puts you somewhere around 30–40% total. If the company is close to an exit, use less; if it is early, use more than feels comfortable.
- What is a vesting cliff?
- A period at the start — usually twelve months — during which nothing vests at all. Leave on day 364 and you have nothing; stay to day 365 and a full quarter of the grant vests at once. It exists to make sure the company is not giving equity to someone who leaves in month three.
- What happens if I leave before an exit?
- You keep what has vested, but you usually have to exercise within 90 days of leaving or forfeit it. That is a real cash decision at a moment when you may not have the cash — a 10,000-option grant at a $1 strike is $10,000 to keep, plus any tax due. Some companies now offer extended exercise windows; it is worth asking before you need to know.
- Are options taxed when I exercise?
- Potentially, and this catches people badly. In the US, exercising an incentive stock option can create alternative minimum tax on the spread between strike and fair market value — tax owed on a gain you have not received in cash and may never realise. This tool does not model tax, and nobody should exercise a large grant without advice.
- What are liquidation preferences?
- The right of investors to be paid before common shareholders in an exit. If a company raised $80m and sells for $100m, preferred holders may take the first $80m and the remaining $20m is split among everyone else — so common stock can be worth far less than the exit price suggests, and at a low enough exit, nothing at all.
- What does underwater mean?
- That your strike price is at or above the current share price, so exercising today would cost more than the shares are worth. It happens after a down round and is not the same as worthless — the options still pay out if the company recovers past your strike. The tool flags it rather than showing a negative number.
- What is a 409A valuation?
- An independent appraisal of a private company's common stock, used to set strike prices for new grants. It is typically well below the preferred share price investors paid, which is why an employee's strike can look cheap next to the headline valuation. It is also the number your exercise spread is measured against for tax.
- Should I negotiate options or salary?
- Salary is certain and options are a lottery ticket with good odds at best. The honest framing is to take the salary you need and treat any option value as upside — and if you are being asked to accept materially below-market pay for equity, a stock option calculator startup employees can check independently is the right place to find out what you are being offered in exchange.
- Do you store the numbers I enter?
- No. The calculation runs entirely in your browser. Nothing is sent to a server, nothing is logged, and there is no account — worth knowing before you type your own compensation into a web page.
- Why is this free, and what is Tekk?
- Tekk is a spec-driven development platform for people building software with AI coding agents. This calculator costs us nothing to run, and an option grant is ultimately a bet on the company shipping — which is the problem we work on. No signup, no run limit, no upsell inside the tool.
Want a real spec for what you’re building?
Drop a sentence. Tekk grounds it in your actual code and turns it into an executable plan.
Free to try · Connect GitHub during signup