Is this what my ownership will really be?

It is a planning model. Real outcomes depend on pool refreshes at each round, whether SAFEs are pre- or post-money, secondary sales and any anti-dilution protection. Use it to compare paths, then model the specific round on your real cap table.

How much do founders typically own at Series B?

Ranges vary widely by sector and geography, but a founding team ending Series B with 30–45% between them is a common shape when rounds sell 15–25% each and pools are refreshed. A single founder's share depends on the founding split.

Can I avoid dilution?

Only by not raising. What you can control is how much you raise, at what price, how large each pool refresh is, and whether convertible instruments stack up before a priced round.

Free tool

Founder ownership calculator

Start from your founding split and walk forward: an option pool, a SAFE that converts, then Seed, Series A and Series B. Each stage shows the founder position after it, so you can see where ownership actually goes.

Your founding ownership (%)

Option pool created (%)

SAFE / convertible converts into (%)

Seed round sells (%)

Series A sells (%)

Series B sells (%)

Founding ownership: 50.00%
After option pool: 45.00%
After SAFE conversion: 41.40%
After Seed: 33.12%
After Series A: 26.50%
After Series B: 21.73%
Total dilution (percentage points): 28.27

How this is calculated

Each round dilutes every existing holder proportionally: ownership after = ownership before × (1 − new investor percentage).
The option pool is treated as a percentage of the company created before the next round's money.
SAFE conversion is entered as the percentage the SAFE takes at the round it converts into.
Rounds are applied in sequence, so the founder position compounds down rather than subtracting.

Worked example

Two founders split 50/50, then create a 10% pool, take a SAFE that converts into 8%, and sell 20% at Seed, 20% at Series A and 18% at Series B. Each founder ends at roughly 12.1% — the compounding, not any single round, is what does the work.

Assumptions

Each round is priced and dilutes every existing holder equally on a fully diluted basis.
Pool increases in a round are created pre-money.
The founder does not buy or sell shares between rounds.

Limitations

Illustrative round sizes are not a forecast of your own outcome.
Does not model converting instruments, down rounds with anti-dilution, or secondary sales.
Says nothing about exit proceeds, which depend on the preference stack rather than percentages.

Prepared by Perseids for general information. This tool runs on the numbers you enter, stores nothing and uses no company data. Results are illustrative and are not legal, tax or investment advice.

Run the same model on your real cap table, with your actual instruments.

Model this on your actual cap table in Perseids

Frequently asked questions

Is this what my ownership will really be?: It is a planning model. Real outcomes depend on pool refreshes at each round, whether SAFEs are pre- or post-money, secondary sales and any anti-dilution protection. Use it to compare paths, then model the specific round on your real cap table.
How much do founders typically own at Series B?: Ranges vary widely by sector and geography, but a founding team ending Series B with 30–45% between them is a common shape when rounds sell 15–25% each and pools are refreshed. A single founder's share depends on the founding split.
Can I avoid dilution?: Only by not raising. What you can control is how much you raise, at what price, how large each pool refresh is, and whether convertible instruments stack up before a priced round.