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Startup Dilution Calculator
See what each funding round does to your ownership — and to the dollar value of your stake. Option pool, YC, seed, Series A and beyond.
Rounds
Final ownership
27.45%
Total dilution
45.1%
Stake value at last round
$16,472,160
Round by round
| Round | Before | After | Stake value |
|---|---|---|---|
| Option pool | 50.00% | 45.00% | $675,000 |
| YC | 45.00% | 41.85% | $747,321 |
| Seed | 41.85% | 34.32% | $4,118,040 |
| Series A | 34.32% | 27.45% | $16,472,160 |
Worked example: two founders from day one to Series A
Two cofounders split the company 50/50, so together they own 100%. Here is how each step changes that, using the rule new ownership = old ownership × (1 − % sold).
| Step | % sold | Math | Founders together | Each founder |
|---|---|---|---|---|
| Option pool | 10% | 100% × 0.90 | 90.0% | 45.0% |
| YC (post-money SAFE) | 7% | 90% × 0.93 | 83.7% | 41.9% |
| Seed | 20% | 83.7% × 0.80 | 67.0% | 33.5% |
| Series A | 20% | 67.0% × 0.80 | 53.6% | 26.8% |
Each founder's percentage roughly halves, from 50% to 26.8%. But if the Series A is priced at a $60M post-money valuation, each founder's stake is worth about $16.1M (26.8% × $60M), compared with a few thousand dollars on day one. That is why investors and experienced founders focus on stake value, not percentage.
Quick SAFE check: a $1M SAFE with a $10M post-money cap converts to 10% ($1M ÷ $10M). Stack three SAFEs like that and founders give up about 27% before a priced round even starts (1 − 0.9³).
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YC takes 7% — here is exactly how
$125K for 7% on a post-money SAFE plus $375K uncapped MFN. Read the terms line by line before you model the rest of your rounds.
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How to use this tool
Step 1
Enter your starting stake
Use the percentage you own today, before any of the rounds below.
Step 2
Adjust the rounds
Set how much of the company each round sells and its post-money valuation.
Step 3
Compare percentage to value
Your percentage always falls; the point is whether your stake's dollar value rises.
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FAQ
How do you calculate equity dilution?
Your new ownership equals your old ownership multiplied by (1 − new investor percentage). If you own 40% and a round sells 20% of the company, you end at 40% × 0.8 = 32%.
How much dilution is normal per round?
Accelerators take 5–7%, seed rounds 15–25%, Series A 15–25%, and each later round 10–20%. Founders who raise through Series B commonly hold 25–40% combined.
Does the option pool dilute founders?
Almost always yes. Investors typically require the pool to be created before their money goes in, so the pool comes out of the pre-round shareholders — the founders.
Is dilution bad?
Only if the money buys nothing. Owning 20% of a company worth $200M beats 80% of a company worth $2M. What matters is the value of your stake, not the percentage.
How does a SAFE dilute founders?
A post-money SAFE converts into a fixed percentage: investment ÷ post-money cap. A $1M SAFE at a $10M post-money cap becomes 10% of the company when it converts, and that 10% comes out of the existing holders.
What is the difference between pre-money and post-money dilution?
Post-money valuation includes the new money. Percentage sold = investment ÷ post-money. Raising $2M at a $8M pre-money means $10M post-money, so investors get 20%.
How much should founders own after Series A?
A common range is 50–65% combined for the founding team after Series A, though it varies widely with how much was raised on SAFEs and how large the option pool is.
Can I avoid dilution?
Only by raising less or at higher valuations, or by growing on revenue. Anti-dilution clauses protect investors in down rounds, not founders.
Is this dilution calculator free?
Yes. No signup and nothing is stored — all math runs in your browser.
Keep reading
Deep dive
The YC SAFE, Explained →
Post-money SAFE mechanics, cap tables, and what founders actually sign.
Playbook
YC Equity Split for Co-Founders →
Why YC pushes 50/50 splits, when to deviate, and vesting basics.
Deep dive
The $500K YC Deal →
How the standard $125K + $375K SAFE actually works.
Fundraising
Post-Money SAFE Explained →
Cap math, dilution tables, MFN clauses and the four standard forms.
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