This calculator measures how a pre-seed financing changes an existing holder’s ownership percentage. Enter ownership before the round and the percentage issued to new investors or other recipients; the page calculates ownership after the round, percentage-point loss, and relative dilution.
It is useful for founders, employees, and early investors comparing fundraising scenarios. The model isolates one dilution event and assumes all existing holders are diluted proportionally. It does not account for pro rata participation, secondary sales, anti-dilution provisions, or changes to the option pool unless those are represented in the new equity percentage.
1. Enter current ownership
Use the holder’s fully diluted percentage immediately before the transaction.
2. Enter new equity issued
Use the post-transaction percentage allocated to new investors, an option pool, or another issuance.
3. Review ownership after
The remaining stake equals current ownership multiplied by the portion not newly issued.
4. Compare scenarios
Change the issuance percentage to see how round structure affects dilution.
Ownership after = Ownership before × (1 − New equity issued) Percentage-point loss = Ownership before − Ownership after Relative dilution = Percentage-point loss ÷ Ownership before
Percentages are converted to decimals during calculation. All existing holders are assumed to dilute proportionally.
The result shows the holder’s post-transaction ownership under the stated issuance percentage.
Cap-table documents should be used for transaction-level precision.
Given: A founder owns 60% before a round that issues 20% of post-money equity.
Calculation: Ownership after = 60% × (1 − 0.20) = 48%. Percentage-point loss = 12 points. Relative dilution = 12 ÷ 60 = 20%.
Result: The founder retains 48% and experiences 20% relative dilution.
Not necessarily. A holder may keep the same number of shares while the total share count increases, reducing the ownership percentage.
Use the post-money percentage issued to new holders, including any pool increase you want included in the scenario.
No. A post-transaction issuance percentage must be between 0% and 100%.
A holder who buys additional shares may offset some or all dilution; this simple model assumes no participation.
Percentage-point loss is the direct drop in ownership; relative dilution measures that drop as a share of the starting stake.