Percentage is shares ÷ total shares. From there:
- Shares for a target %:
new shares = existing × p / (1 − p).
- Each investor's % = their cash ÷ post-money valuation. Within a round everyone buys at the same price per share.
- Dilution: every holder keeps their share count, but the total grows each round, so their % shrinks - shown in the ownership-over-time chart.
- Convertible notes / SAFEs: a note converts at the better of its valuation cap or its discount to the round's price, plus any accrued interest. It converts into the pre-money, so the founders absorb the dilution while the round's new investors keep their negotiated %. A note left as debt to exit does not convert - instead it is repaid first (see below).
- Exit waterfall: any convertible notes still outstanding as debt are repaid first - principal plus interest, senior to all equity; then liquidation preferences are paid; non-participating preferred take the greater of their preference or converting to common; the rest splits pro-rata.
Waterfall assumptions: preferences rank equally (pari passu), participation is uncapped, and option-pool shares count as common (strike price ignored). The founding share count is arbitrary - only the split matters.