Pre-money vs post-money valuation: formulas, ownership, and pitfalls

Learn pre-money vs post-money valuation, how investor ownership is estimated, and why the option pool shuffle changes effective dilution.

Updated 2026-01-28

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Definitions

  • Pre-money valuation: the company value before new investment.
  • Post-money valuation: the company value after new investment (often pre-money + investment, simplified).
  • Ownership: the percent of the company after the round on a fully diluted basis (the basis matters).

Core formulas (simplified)

  • Post-money = pre-money + investment.
  • Implied investor ownership ~ investment / post-money.
  • Existing holders' combined ownership ~ pre-money / post-money.

Why founders get surprised (option pool shuffle)

Many term sheets require increasing the option pool before the investment and counting the pool in the pre-money. This shifts dilution onto existing holders (founders and prior investors). The headline valuation can look the same while founder ownership drops more than expected.

Common mistakes

  • Using ownership on an issued-shares basis instead of fully diluted.
  • Ignoring SAFEs/notes converting in the priced round (dilution stacks).
  • Treating investment / post-money as exact without building a cap table.

FAQ

Is post-money always pre-money + investment-
Often as a simplified framing, yes. But term details like option pool increases, convertible instruments, and fees can change effective ownership outcomes.

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