Cap Table + Dilution Calculator
Model founder dilution through a SAFE round + priced round, using the standard YC post-money SAFE convention. Walks the option pool refresh, SAFE conversion (cap vs. discount, lesser of), and priced-round price-per-share derivation. Source-cited to YC, Brad Feld's Venture Deals, and Carta.
1,111,111 shares (7.27%)
| Holder | Shares | % |
|---|---|---|
| Founders | 10,000,000 | 90.00% |
| Option pool | 1,111,111 | 10.00% |
| Total | 11,111,111 | 100% |
| Holder | Shares | % |
|---|---|---|
| Founders | 10,000,000 | 81.82% |
| Option pool | 1,111,111 | 9.09% |
| SAFE | 1,111,111 | 9.09% |
| Total | 12,222,222 | 100% |
| Holder | Shares | % |
|---|---|---|
| Founders | 10,000,000 | 65.45% |
| Option pool | 1,111,111 | 7.27% |
| SAFE | 1,111,111 | 7.27% |
| Priced investors | 3,055,556 | 20.00% |
| Total | 15,277,778 | 100% |
Visualization: percentage breakdown by stakeholder across the three fundraising stages. Note: founders' slice shrinks while the cap table grows.
View the TypeScript implementation on GitHub: packages/calc/src/cap-table.ts · view tests
What this means
Every fundraising round adds shares to the cap table, and every new share comes out of someone's ownership percentage. The option pool comes out of founders alone (pre-money allocation). The SAFE comes out of founders + pool (because the SAFE converts before the priced round). The priced-round investors come out of everyone — founders, pool, and SAFE holders. The compounded effect is what appears in the "founder dilution total" number. Most founders are surprised by how big it is the first time they model it end-to-end.
The single biggest lever in this math is the option pool. A 10% pool creates ~11% pre-money dilution for founders; a 15% pool creates ~17.6%. Investors push for larger pools precisely because every percentage point of pool comes out of founders alone, not investors. The defensible negotiation: build an 18-month hiring plan, sum the equity grants, and use that number — not the term-sheet template default — as your pool size.
Worked example — the YC-default scenario
Two founders incorporate at 10,000,000 shares (5M each). Term sheet calls for a 10% post-money option pool, allocated pre-money. They previously raised a $1M SAFE at a $10M post-money cap with a 20% discount. Now they're closing a $5M Series Seed at $20M pre-money.
Pool refresh: 10M × 0.1 / 0.9 ≈ 1,111,111 option shares. Pre-SAFE total = 11,111,111.
SAFE conversion: cap-price = $10M / 11.111M = $0.90/share. Initial priced-price = $20M / 11.111M = $1.80. Discount-price = $1.80 × 0.8 = $1.44. The SAFE converts at the lesser — $0.90/share, the cap. SAFE shares = $1M / $0.90 ≈ 1,111,111.
Priced round: pre-priced total = 12,222,222. Price/share = $20M / 12.222M ≈ $1.6364. Priced shares = $5M / $1.6364 ≈ 3,055,556. Post-priced total = 15,277,778.
Founder ownership: 10M / 15.278M ≈ 65.45%. Founders started post-pool at 90%, so they diluted ~24.5 percentage pointsin this single round. Two founders splitting that means each owns ~32.7% post-priced. Read this number carefully — at the next round (Series A), they'll dilute another 15-20pp on top of this. The cap table compounds.
Frequently asked questions
The information and tools on this website are for general educational purposes only and do not constitute financial, investment, legal, or tax advice. Consult a licensed professional for decisions specific to your situation.