Option pool sizing
Option pool calculator: what an ESOP top-up really costs founders
A bigger option pool at the same pre-money valuation is a lower effective price for founders. Enter your round terms and target pool size to see founder dilution with the top-up compared against none at all.
The pool top-up is created pre-money— it dilutes only the founders (and any SAFEs converting in this round), never the new investor’s target ownership.
| Stakeholder | Type | Invested | Shares | Ownership |
|---|---|---|---|---|
| Founders | Common | — | 10,000,000 | 68.26% |
| Option Pool | Options | — | 1,464,968 | 10.00% |
| New round | Preferred | $5M | 3,184,713 | 21.74% |
| Total (fully diluted) | 14,649,681 | 100% | ||
How it works
1. Start from your fully-diluted shares
2. Set the round and the target pool
3. Compare with vs. without
4. Remember: it's pre-money
Frequently asked
Why does the option pool dilute founders and not the new investor?+
Because it's created pre-money. The investor negotiates for a fixed post-money ownership percentage; the pool top-up is added to the pre-money share count to hit the target pool percentage, which comes entirely out of existing holders' slice of the pie — this is often called the "option pool shuffle."
What's a typical option pool size?+
10–15% fully diluted, post-round, is the most common range for an early-stage round, though it varies with hiring plans and prior grants. There's no universal number — it should be sized to the roles you actually plan to hire.
Does this account for an existing option pool, or only a fresh top-up?+
This calculator models a fresh pool built from zero to your target percentage in one round. For a scenario with an existing pool plus a top-up, use the cap table calculator, which accepts a starting pool size directly.
Should I negotiate the pool size before or after the price?+
Before. The pool size and the pre-money valuation are effectively the same negotiation — a bigger pool at the same pre-money is a lower price for founders. Model both together here before agreeing to either number.
Need this in your own tool or agent?
The exact same engine is available as a JSON API — one key, deterministic results, an OpenAPI spec and an MCP server.