How much does a founder's ownership shrink after three funding rounds?

Using 2026 median deal terms — a $2M seed at $18.4M pre-money, an $8M Series A at $45M pre-money, and a $20M Series B at $120M pre-money — a starting 100% stake falls to about 65.6% after all three rounds, in a simplified model that only accounts for the dilution from the raise itself.

Why is 65.6% higher than published founder retention statistics?

Published survey data (WaveUp, CRV) puts median founder retention closer to 56% after seed, 36% after Series A, and 23% after Series B. The gap exists because investors commonly require an option-pool refresh — topping up the employee equity pool from existing shareholders' stakes — as a condition of the round, on top of the dilution from the raise amount alone.

What's the formula for dilution in a single funding round?

New investor percentage equals the amount raised divided by the post-money valuation (pre-money valuation plus the raise). Every existing shareholder's ownership is then multiplied by (1 minus that new investor percentage).

What is an option pool refresh and why does it matter for dilution?

An option pool refresh expands the pool of shares reserved for future employee equity grants, funded by diluting existing shareholders — typically founders — before new investor money comes in. It's a standard term in most priced rounds but isn't captured by a simple raise-amount-only dilution calculation.

Seed to Series B: A 100% Founder Stake Falls to 65.6% Before Any Option Pool Even Enters the Math

Three funding rounds, 2026 median deal terms, one founder’s stake tracked from 100% down through each round. The numbers move faster than the round-by-round intuition most first-time founders start with.

The three-round trajectory

Round	Raise	Pre-money	New investor %	Ownership after
Seed	$2M	$18.4M	9.8%	90.2%
Series A	$8M	$45M	15.1%	76.6%
Series B	$20M	$120M	14.3%	65.6%

At the Series B’s $140M post-money valuation, that 65.6% stake is worth roughly $91.9M — still a life-changing outcome, but a reminder that “raising money” and “keeping the company” pull in opposite directions with every round, even when each individual round’s terms look reasonable in isolation.

Why real dilution usually runs worse than this

This model only accounts for the mechanical dilution of the raise itself: new investors buy a slice of the post-money company, and everyone who held shares before retains their pre-round share of what’s left. What it doesn’t model is the option-pool refresh — a near-universal term where investors require the employee equity pool to be topped up from existing (mostly founder) shares before their money comes in. Published survey data puts founder retention meaningfully lower than this simplified math: roughly 56% after seed alone, 36% after Series A, and 23% after Series B. The gap between 65.6% and 23% is almost entirely option-pool math this tool doesn’t capture — worth internalizing before treating any simplified dilution estimate as the real number going into a term sheet negotiation.

Where this calculation doesn’t apply

Your round includes an option-pool refresh (most do). This is the single biggest source of divergence between this simplified model and real outcomes — ask directly what pool size investors expect before signing.
You’re raising on a SAFE or convertible note. These convert into equity later under different mechanics (discount rates, valuation caps) than a straightforward priced round.
Multiple co-founders hold different individual stakes. Run the simulation per-founder using each person’s own starting percentage rather than a shared team total.
Pro-rata rights or anti-dilution provisions apply to specific investors. Some investors have contractual protections against future dilution that this tool doesn’t model.

What to actually do

Model your own actual round terms — pre-money valuation and raise size vary widely by company traction and market conditions, and the defaults here are illustrative benchmarks, not predictions for any specific company.
Ask investors directly whether an option-pool refresh is a condition of the round, and how large — then treat this tool’s output as an optimistic upper bound, not a final number.
Before signing a term sheet, get a real cap-table model that accounts for the pool refresh and any preference stack — this tool is for pre-negotiation intuition, not the negotiation itself.
After each actual round closes, compare the real outcome to what was modeled going in, to calibrate expectations for the next round.

For the equity split this dilution gets applied to in the first place, see Co-Founder Equity Split, and for the runway math that determines when the next round becomes necessary, see Startup Runway Simulator.

Open the Equity Dilution Simulator → and model your own round terms.