Equity Dilution Calculator
Track how your ownership percentage changes through multiple funding rounds and calculate pro-rata investment to maintain your stake.
How Equity Dilution Works
What is dilution?
When a company raises new funding, it issues new shares. This increases the total share count, which reduces every existing shareholder's percentage ownership — even though you still own the same number of shares. This is called dilution.
New Shares vs. Investment + Valuation
You can model a round two ways: (1) specify the number of new shares issued directly, or (2) specify the investment amount and pre-money valuation. The price per share = pre-money / existing shares, and new shares = investment / price per share.
Pro-Rata Rights
Pro-rata rights allow an investor to invest additional capital in future rounds to maintain their ownership percentage. The pro-rata investment needed = your current ownership % × total new investment in that round. Many term sheets include pro-rata rights for major investors.
Cumulative Dilution
Each round compounds. If you are diluted 20% in Series A and then 20% again in Series B, your cumulative dilution is not 40% — it is 36% (0.8 × 0.8 = 0.64 remaining). This calculator tracks compounded dilution accurately.