Share Dilution Calculator
Enter current shares outstanding and new shares issued (secondary offering, SBC, or convertibles). See how much your ownership stake shrinks if you don't buy more.
How to read this number
Dilution percent tells you how much of the newly enlarged share count the new shares represent. Ownership after tells you what happens to a holder who does nothing — their stake shrinks even though they didn't sell anything. Whether that trade-off is worth it depends entirely on what the company does with the capital raised, which this calculator doesn't and can't evaluate for you.
Formula & assumptions
Common questions
What is stock dilution?
Stock dilution happens when a company issues new shares, which reduces each existing shareholder's percentage ownership of the company unless they buy proportionally more shares.
How do you calculate dilution percentage?
Dilution percentage equals new shares divided by the total of current shares plus new shares. A holder who does not buy more sees their ownership percentage fall by roughly that amount.
Is dilution always bad for shareholders?
Not necessarily. Dilution reduces ownership percentage, but whether it is good or bad for a holder also depends on how the company uses the capital raised from issuing those shares.
Go deeper
Want the full picture on a dilution event — not just the math? Run a research pass in AlphaLens.
Run this idea through AlphaLens → Start free trial