Founder Dilution: What to Expect Seed to Series B

Published 2026-08-02

TL;DR

Typical founder dilution: seed ~20%, Series A ~22%, Series B ~18%. After three rounds, founders keep roughly 40-55% collectively.

The formula

post_money = pre + round. new_investor_pct = round / post_money. If the option pool expands p% pre-money, founder dilution = new_investor_pct + p.

Worked example: a “normal” path

Seed: raise $2M at $8M pre, 10% option pool top-up. Post-money $10M. Investor 20%. Pool 10%. Founder dilution: 30%.
Series A: raise $10M at $30M pre, 5% top-up. Post-money $40M. Investor 25%. Pool 5%. Existing dilution: 30%.
Series B: raise $25M at $100M pre, 3% top-up. Post-money $125M. Investor 20%. Pool 3%. Dilution: 23%.

Starting founder ownership 100% → after seed 70% → after A 49% → after B 37.7%. Split across two co-founders: ~19% each remaining.

Try it in the cap table calculator.

Why option pool is a hidden dilution

Pre-money option pool expansion sits on the founders’ side. Investors get their percentage post-money; the pool is bundled with the pre-money valuation. That means every 1% of pool top-up pre-round dilutes existing holders by 1%.

The lever: ask for the pool to be sized to grants planned in the next 12 months, not “for the next round”. A 5% pool covers most seed teams to Series A. Anything above is a giveaway.

Where founders lose more than they should

Oversized bridges. Bridge rounds with valuation caps below the last round convert into big dilution at the next priced round.
Anti-dilution provisions. Weighted-average and full-ratchet clauses can hit founders in a down round. Read the docs.
Advisor equity. 0.25-1% per advisor sounds small until you have five.
Departed co-founders with un-vested acceleration. Poor equity documents cost the remaining team.

Where founders can hold more

Raise less, tighter runway (harder now, but the equity cost of every extra dollar compounds).
Bootstrap to real revenue before priced round; angel money buys time at lower dilution.
Two-tranche seed: first close smaller, second close after a milestone at a higher valuation.
Push option pool creation post-money (rare, but exists).

Common mistakes

Not modeling SAFE conversion before the priced round. Uncapped SAFEs surprise nobody; capped SAFEs at low caps eat into the priced-round dilution.
Ignoring the effect of ISOs vs NSOs on the pool sizing math.
Modeling investor stake without the option pool.
Assuming pro-rata rights don’t matter until they do (usually Series A onward).

Try the calculator

Cap Table Dilution Calculator

Interactive. Shareable via URL. No signup.

FAQ

Is 20% at seed a rule?+

It is a norm, not a rule. Hot rounds close at 10-15%. Slower rounds at 25-30%. Solo GP checks sometimes sit at 5%.

Can I negotiate the option pool?+

Yes. Ask for a smaller pool (only what will be granted before Series A), post-money treatment, or shifted post-close.

How much do co-founders typically hold at Series B?+

Collectively 35-55% is normal. Below 25% often triggers a governance conversation with the board.

What about super-pro-rata?+

Not standard at seed; common at Series A onward. It reserves the right to invest above pro-rata in future rounds, protecting an investor from dilution.

Does SAFE conversion count as its own round?+

No. SAFEs convert at the next priced round. Model the priced round with all SAFEs on the cap table before running dilution numbers.