An option pool refresh is the increase in shares available in the option pool, typically negotiated as part of a priced funding round. The critical structural question is whether the new pool shares are added pre-money (diluting existing stockholders, particularly founders) or post-money (diluting all stockholders proportionally including new investors). It is one of the most economically significant negotiation points in any priced round, and the founder dilution impact of pre-money pool refresh is often larger than the dilution from the investment itself.
The pre-money vs post-money option pool math: