TL;DR

Pre-money valuation is the company's value before new investment; post-money valuation is the value after. The difference is the investment amount. Getting this math wrong is one of the most common and costly founder mistakes.

The Core Formula

Post-money valuation = Pre-money valuation + Investment amount

Investor ownership % = Investment amount ÷ Post-money valuation

Example:

  • Pre-money: $8M + Investment: $2M = Post-money: $10M
  • Investor ownership: $2M ÷ $10M = 20%

Why This Matters

"We're raising at a $10M valuation" — is that pre-money or post-money?

  • Pre-money $10M: Post-money = $12M. Investor owns 16.7%
  • Post-money $10M: Pre-money = $8M. Investor owns 20%

The difference is 3.3 percentage points of ownership.

The Option Pool Shuffle

Investors typically require the option pool be created pre-money, diluting founders (not investors). Calculate the "true" pre-money by subtracting the option pool value from the stated pre-money valuation.

Dilution Across Multiple Rounds

  • Seed: Raise $1M at $4M post-money → Founder owns 75%
  • Series A: Raise $5M at $20M post-money → Founder diluted 25% → owns ~56%
  • Series B: Raise $15M at $60M post-money → Founder diluted 25% → owns ~42%

Key Takeaways

Key Takeaways
  • Post-money = Pre-money + Investment. Always clarify which valuation is being quoted.
  • Investor ownership = Investment ÷ Post-money valuation.
  • The option pool shuffle reduces founder economic ownership — model it carefully.
  • Dilution compounds across rounds — model your ownership through Series B and beyond.
  • A higher pre-money valuation means less dilution per dollar raised.