The Investor Ownership Calculator estimates an investor’s post-round percentage from a new investment, pre-money valuation, and any stake the same investor already owns. The existing stake is diluted alongside other pre-round holders, while the new money purchases an additional post-money percentage. This distinction matters in insider-led or follow-on rounds, where simply adding the old percentage to the new-money percentage overstates ownership. The model gives a clean first-pass result before option pools, conversions, or preferential rights are added.
1. Enter the new investment
Use the investor’s primary purchase amount in the current round.
2. Enter pre-money valuation
Use the agreed value before the round.
3. Enter existing ownership
Use the investor’s fully diluted pre-round percentage, or zero for a new investor.
4. Review the components
The calculator separately shows the diluted old stake and ownership purchased with new money.
Where:
Assumptions: Only this investor supplies new money, and there are no other share issuances, conversions, or option-pool changes.
The total combines newly purchased ownership with the investor’s diluted pre-round stake.
When multiple investors participate, use the entire round size to calculate dilution, then allocate the new-money ownership by each investor’s share of the round.
Given: Investment = $2M, pre-money valuation = $8M, existing ownership = 5%.
Calculation: New-money ownership = $2M ÷ $10M = 20%. Retained old stake = 5% × 80% = 4%. Total = 20% + 4% = 24%.
Result: The investor owns an estimated 24% after the financing.
New shares increase the fully diluted share count, so every pre-round holder’s percentage is diluted.
No. The old percentage must first be reduced by the round’s dilution factor.
Calculate total round dilution using the full financing amount, then assign new shares among investors according to their investments and price.
A secondary purchase transfers ownership from a seller and does not create the same company-wide dilution as newly issued shares.
An investor can often preserve a target percentage by purchasing enough of the new issuance, but the exact right and amount depend on the financing terms.