Dilution is the drop in your ownership percentage that happens when a company issues new shares. Your share count stays the same, but the total number of shares grows, so each share you hold represents a smaller slice of the company.

Every priced financing round, option grant, and convertible conversion dilutes the existing owners. Founders should expect to give up meaningful ownership at each stage. The goal is not to avoid dilution but to make sure each round buys enough value to justify it.

How dilution works

Say you own 4,000,000 shares of a company with 10,000,000 shares outstanding, so you hold 40 percent. The company then issues 2,500,000 new shares to a Series A investor. Now 12,500,000 shares are outstanding, and your 4,000,000 shares equal 32 percent. You did not lose any shares, but your percentage fell. That is dilution, and you track it on your cap table.

Percentage dilution versus economic dilution

Percentage dilution and economic dilution are different things, and founders confuse them. Percentage dilution is the drop in your ownership stake. Economic dilution is a drop in the per-share value of what you own. A round can dilute your percentage while increasing your economic value, because the new money and a higher valuation make the whole company worth more. A down round does the opposite, cutting both your percentage and your per-share value. This is why investors negotiate anti-dilution protection, which adjusts their conversion terms to soften economic dilution in a down round.

The option pool shuffle and managing dilution

Watch the option pool. Investors often require you to create or expand an option pool before their money goes in, and they size that pool into the pre-money valuation. The effect, sometimes called the option pool shuffle, is that the new pool dilutes the existing shareholders alone and not the incoming investor. You can push back on the pool size, because an oversized pool transfers ownership straight from the founders to the investor. If you hold a pro rata portion right, you can also buy into future rounds to defend your percentage.

This is general information, not legal advice.