The Seed Stage Dilution Calculator estimates how a new financing round changes an existing holder’s ownership percentage. It uses pre-money valuation, new investment, and current ownership to show post-money dilution and the implied value of the remaining stake.
The model is a simplified financing view. Option-pool increases, convertible instruments, liquidation preferences, and transaction terms can change the actual capitalization outcome.
Use the agreed company equity value immediately before the new investment.
Enter the primary capital issued in the round.
Use the holder’s fully diluted percentage before the round.
Compare the remaining percentage with the pre-round stake.
Model option-pool changes or convertible conversions separately if they occur with the round.
Post-money valuation = Pre-money valuation + New investment
Existing holder post-round ownership = Current ownership × (Pre-money ÷ Post-money)
Dilution = Current ownership − Post-round ownership
The formula assumes only newly issued primary equity and no other capitalization changes.
Post-round ownership is the holder’s estimated percentage after the new investor receives newly issued shares.
Economic rights may differ from percentage ownership because of preferences, option pools, and security terms.
Given: A $6 million pre-money valuation, $2 million new investment, and 20% current ownership.
Calculation: Post-money value = $8 million. Retention factor = $6m ÷ $8m = 75%. New ownership = 20% × 75% = 15%.
Result: The holder falls from 20% to 15%, a 5 percentage-point dilution.
Not necessarily. A smaller percentage of a more valuable company can have equal or greater implied value.
If created before the financing, it can dilute existing holders further. This simplified model does not include that adjustment.
Yes. Their conversion can increase the fully diluted share count and alter ownership before or during the round.
Pre-money valuation determines how much ownership the new cash buys before considering the investment itself.
No. Voting rights can depend on share class, board rights, agreements, and protective provisions.