Equity Dilution Calculator for Startups
See how much of your company you actually keep after a sequence of funding rounds. Set your starting stake, then add each round's raise, pre-money valuation and option pool to watch your ownership dilute over time.
Your stake
Funding rounds
Each round issues new shares, so your percentage shrinks. Add the raise, the pre-money valuation and any new option pool (carved pre-money).
Round-by-round dilution
| Round | Raise | Post-money | Round dilution | Your % after | Your value |
|---|
How equity dilution works across rounds
Every priced round issues new shares. Your share count doesn't change, but the total grows, so your percentage falls. For a single round the new investor takes raise ÷ post-money (post-money = pre-money + raise). A new option pool is usually carved pre-money, which dilutes existing shareholders, including you, on top of the investor's stake.
Across several rounds, dilution compounds. If you keep 80% through a round and 85% through the next, you're left with 0.80 × 0.85 = 68% of what you started with. This calculator applies each round in order and multiplies the effect, so the final number reflects the full Seed → Series A → B → … path, not just one round.
Worked example: Seed, Series A and Series B
A founder starts with 100% and raises three priced rounds, each with a new option pool carved pre-money.
| Round | Raise | Pre-money | Pool | Post-money | Round dilution | Your % after |
|---|---|---|---|---|---|---|
| Seed | $1.5M | $6.0M | 10% | $7.5M | 30.0% | 70.0% |
| Series A | $6.0M | $24M | 5% | $30M | 25.0% | 52.5% |
| Series B | $15M | $70M | 5% | $85M | 22.6% | 40.6% |
| After 3 rounds | $85M | 59.4% total | 40.6% |
Round dilution is the investor stake (raise ÷ post-money) plus the new pool: 20.0% + 10% at Seed, 20.0% + 5% at Series A, 17.6% + 5% at Series B. The founder's 40.6% of the $85M Series B post-money is worth $34,518,750.
Dilution compounds: your stake after several rounds is your starting stake multiplied by (1 − dilution) for each round, which is why the default example ends near 40% after three rounds. To protect ownership, focus on round size, valuation and how large a pool each investor asks you to create. For the full per-shareholder breakdown of a single round, use the cap table calculator; to plan the raises themselves, see the SaaS fundraising guide. This tool is a fast estimate, not legal or investment advice.
Frequently asked questions
How do you calculate equity dilution?
How much equity do you give up in each funding round?
How does dilution compound across rounds?
Does the option pool dilute founders?
Does dilution lower the value of my shares?
Does this calculator handle SAFEs and convertible notes?
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Cite this page
Citation
Adlega. "Equity Dilution Calculator for Startups: Per Round." Updated October 22, 2026. https://adlega.com/blog/tools/dilution/
Link for your article
<a href="https://adlega.com/blog/tools/dilution/">Equity Dilution Calculator for Startups: Per Round</a> (Adlega, updated October 22, 2026)
Model dilution against runway and hiring
Adlega ties your ownership to the actual financial plan, so you can see how each raise affects dilution, runway and the milestones it has to buy.