The method
How it is worked out
Post-round ownership = pre-round ownership × (1 − new investor post-money %)
- pre-round ownership
- Your percentage before the new issue
- new investor %
- Post-money ownership issued to the new investor
Equity Dilution Calculator
Calculate ownership dilution after a new investment round or share issue. The result updates as you type so you can compare scenarios quickly.
Keep in mind
What it leaves out
- Option poolsNew or refreshed option pools can add further dilution.
- Multiple securitiesConvertibles, SAFEs and preferences need cap-table modelling.
- Economic rightsVoting and liquidation rights can differ from headline ownership.
Use the calculator to compare scenarios rather than as a guaranteed forecast.
About the Equity Dilution Calculator
Estimate how a new funding round changes an existing owner's percentage of a company. This helps a founder understand the percentage effect of selling new equity before considering the round's financial terms.
How it works and an example to tryShow less
How to use the result
The existing ownership percentage is multiplied by one minus the new investor's post-money ownership fraction. The tool shows percentage dilution under that simplified share-issue assumption. Option-pool expansions, existing preferences, convertible notes and secondary share sales can change the actual cap table; this calculation does not price the business.
Example to try
If you own 70% before the round and new investors receive 15% post-money, enter those percentages to inspect the remaining holding. Repeat with a larger investor stake. Compare a full post-round cap table before signing rather than using this single holding in isolation.
Put it to work
Try it on a real situation
Load an example
What moves the result most
Worked out from your figures above. Tap a row to try it.
Who uses it, and when
Founders modelling a funding round, employees estimating what their options will be worth after a raise, and angel investors checking their stake after later rounds.
Mistakes worth avoiding
- Ignoring the option pool the investor asks you to create before their money lands.
- Assuming a higher valuation always leaves you better off than raising less.
- Forgetting convertible notes that will convert into shares at the round.
Questions
What does the Equity Dilution Calculator do?
Calculate ownership dilution after a new investment round or share issue.
How should I use the result?
The existing ownership percentage is multiplied by one minus the new investor's post-money ownership fraction. The tool shows percentage dilution under that simplified share-issue assumption. Option-pool expansions, existing preferences, convertible notes and secondary share sales can change the actual cap table; this calculation does not price the business.
Does TechBullion store the information I enter?
The core calculation or transformation runs in your browser. Normal website security and analytics may still record page-level events, but the tool does not need to create a public record from your inputs.
What mistakes do people make with an equity dilution calculator?
Ignoring the option pool the investor asks you to create before their money lands. Assuming a higher valuation always leaves you better off than raising less. Forgetting convertible notes that will convert into shares at the round.
Is the result guaranteed?
No. Use the result as a practical check or planning aid and verify important decisions with the relevant primary source, provider or professional advice.
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Calculator results are estimates based on the figures entered and are not financial, investment, legal or tax advice.