How equity dilution works, round by round

Dilution is what happens to your ownership percentage every time the company sells new shares to raise money. Your share count usually stays the same, but the total number of shares goes up, so the percentage you own goes down. A grant that was 0.5 percent at seed can easily be 0.32 percent by the time the company closes a Series B, and that is normal, not a sign anyone cheated you.

The part most engineers miss is that a smaller percentage of a much bigger company is often worth far more in dollars. This post follows one grant through three rounds with real numbers so you can see exactly where the percentage goes and what it does to the dollar value. If you are still deciding what to ask for in the first place, start with what to ask about startup equity and how much equity by stage, then come back here for the round-by-round math.

Why does raising money dilute me?

A startup raises money by issuing new shares and selling them to investors. Nobody takes shares away from you. The company prints new ones, which grows the denominator. You owned a slice of a pie, the company baked a bigger pie, and your slice is now a smaller fraction of the whole.

Here is the one formula that drives everything below. After a round, your new percentage is your old percentage multiplied by (pre-money valuation divided by post-money valuation). Post-money is just pre-money plus the new cash raised. So if investors put in 25 percent of the post-money value, everyone who was already there gets diluted by 25 percent.

Your share count does not change when the company raises. The total share count grows, so your percentage shrinks. That is dilution.

A worked example: one grant through seed, A, and B

Start with a clean setup. You join right after the seed round as an early engineer. The company has 10,000,000 shares outstanding and grants you 50,000 options. That is 0.5 percent on a fully diluted basis. Watch what each subsequent raise does to that 0.5 percent. (illustrative, not advice)

Your 0.5 percent became 0.375 percent after the A (a 25 percent haircut), then 0.281 percent after the B (another 25 percent). Over two rounds you lost about 44 percent of your percentage. If you only look at the percentage, it feels like you are bleeding ownership. Now look at what the same slice is worth in dollars.

Why is a smaller slice worth more?

Multiply your percentage by the company's post-money valuation at each step. The percentage shrinks, but the valuation it is a percentage of grows faster, so the paper value goes up.

Your percentage fell by 44 percent, but the paper value of your grant grew by more than 5x, from $60,000 to $337,500. That is the whole point of taking dilution: you trade percentage for the capital that makes each remaining percentage worth more. A founder who refuses to dilute keeps 100 percent of a company that ran out of money.

What about the option pool? The hidden extra dilution

There is a second source of dilution that catches people off guard: the option pool top-up. Before a priced round, investors usually require the company to create or expand an option pool for future hires, and they require it to come out of the pre-money valuation. That means the existing shareholders (founders and early employees like you) absorb that dilution, not the new investors.

Concretely, if a Series A requires a 10 percent post-money option pool and the existing pool is small, refreshing it can add a few percentage points of dilution to everyone already on the cap table, on top of the dilution from the new money itself. This is sometimes called the option pool shuffle. It is one reason your real after-round percentage is usually a little lower than the clean (pre-money / post-money) math suggests. When you read an offer, ask whether the quoted percentage is before or after any planned pool expansion.

Does anti-dilution protection apply to me?

Mostly no, and it helps to know why. Anti-dilution provisions protect preferred shareholders (the investors), not employees holding common stock or options. They kick in during a down round, when the company raises at a lower price than a previous round.

There are two common flavors. Full ratchet repsices the earlier investor's shares as if they had paid the new lower price, which is harsh and rare. Weighted average adjusts more gently based on how much was raised at the lower price, and it is the market standard. Either way, when investors get their anti-dilution adjustment in a down round, the extra shares come from somewhere, and that somewhere is the common stock pool. So anti-dilution does not protect you. It can actually dilute you more in a down round, because you are the one absorbing the investor's protection.

• You hold: common stock or options. No anti-dilution protection in almost all cases.
• Investors hold: preferred stock, usually with weighted-average anti-dilution.
• In a down round: investor protections convert into more preferred shares, diluting common holders (you) further.
• What you can negotiate instead: the size of the grant, the strike price, and the vesting terms, not anti-dilution. See how to negotiate a startup offer.

How do I estimate my dilution before signing?

You cannot predict the future cap table, but you can build a rough model in five minutes and avoid being surprised.

1. 01Get your starting percentage on a fully diluted basis. Grant size divided by total fully diluted shares. If they will not give you the share count, that is a signal in itself.
2. 02Assume roughly 20 to 25 percent dilution per future priced round. This is a reasonable planning number, not a promise. Multiply your percentage by 0.78 or so per expected round.
3. 03Count the rounds to a likely exit. A seed-stage company might raise an A, B, and C before any liquidity. Three rounds at 22 percent each leaves you with about 47 percent of your starting percentage.
4. 04Pair it with a valuation guess at exit. Multiply your diluted percentage by a conservative exit value to get a dollar range. Then haircut heavily for risk, because most startups do not reach a large exit. See is startup equity worth it.
5. 05Sanity-check against comp you are giving up. If the cash offer is well below market, the equity has to do real work over 4 years of vesting to make up the gap.

When should dilution actually worry you?

Normal dilution from healthy rounds is good news in disguise: it means the company keeps raising at higher prices and the pie keeps growing. The dilution that should worry you is the kind tied to bad terms or trouble. A down round dilutes you and signals the valuation fell. A round with a heavy liquidation preference can mean investors get paid back several times over before common stock sees a dollar, which quietly erases the value of your slice even if the percentage looks fine. And a company that raises constantly without growing is just trading your ownership for runway.

The cleanest defense is joining a company whose last round was recent, large enough to fund a real plan, and priced up rather than down. That is exactly the signal the roles.cc board is built around. Every role is sorted by how recently the company raised, so you can favor companies in a strong post-raise window over ones quietly running low. You can watch the recent raises directly.