Equity Dilution Calculator

About this calculator

When a startup issues new shares in a funding round, existing shareholders keep the same number of shares but now own a smaller slice of a bigger pie — this calculator computes your post-round ownership as your shares ÷ (total shares before the round + new shares issued), showing both your new percentage and how many percentage points you were diluted by.

Founders negotiating a term sheet, early employees evaluating stock options, and angel investors deciding whether to exercise pro-rata rights use this to understand the real cost of raising capital before signing: a $2M raise on an $8M pre-money valuation dilutes existing holders by 20%, for example, regardless of how the deal is framed. Anti-dilution provisions, option pool expansions, and convertible notes can change the exact math, but the core share-count ratio is the starting point for any dilution analysis.