Employee Stock Option Dilution Explained
Employee stock options (ESOPs) are one of the most overlooked sources of founder dilution. Understanding how option pools work, how they are sized, and when they dilute you is essential before your first institutional raise.
What is an Employee Option Pool?
An employee option pool is a block of shares set aside to be granted to employees, advisors, and contractors as equity compensation. These shares do not yet belong to anyone - they are reserved for future grants. As grants are made, they dilute all shareholders proportionally.
Most VCs require a refreshed option pool of 10-20% to be in place before they invest at Series A. The timing of when this pool is created - before or after the investment is priced - has a major impact on who bears the dilution cost.
The Option Pool Shuffle
The option pool shuffle is a negotiating tactic where investors require the option pool to be included in the pre-money valuation rather than the post-money valuation. This means the pool is carved out of the existing shareholder base before the investor buys in - so only founders and existing investors absorb the dilution.
Example: Pre-money vs Post-money option pool
Option pool pre-money (investor preference)
- Pre-money valuation: $10M
- Option pool created: 15% (1.76M shares)
- Effective pre-money for founders: $8.5M
- Investor invests $2M, owns 19%
- Founders absorb all pool dilution
Option pool post-money (founder preference)
- Pre-money valuation: $10M
- Investor invests $2M, owns 17%
- Option pool created from post-money
- All parties diluted proportionally
- Founders retain more effective ownership
Always model both scenarios before accepting term sheet language around option pools. The difference can be 3-8 percentage points of effective founder ownership.
Vesting Schedules and Cliff Periods
Options are not granted all at once - they vest over time. The standard vesting schedule in US and UK startups is a 4-year vest with a 1-year cliff. This means an employee earns nothing for the first 12 months, then receives 25% of their total grant on the cliff date, followed by monthly or quarterly vesting for the remaining 3 years.
From a dilution perspective, ungranted options in the pool dilute all shareholders immediately because they are included in the fully diluted share count. Unvested but granted options also appear in the fully diluted count. This is why understanding fully diluted ownership rather than basic ownership is critical for founders assessing their true economic stake.
How Large Should Your Option Pool Be?
Investors often request larger pools than necessary as a negotiating position. You should model exactly how many grants you plan to make over the next 18-24 months and only expand the pool to cover that amount plus a reasonable buffer.
Typical option pool sizes by stage