Calculate Ownership Percentage
Formula Used
The calculator uses the entered share classes as a simplified cap table.
When the fully diluted option is checked, existing option pool shares are added to the pre-change denominator.
New shares, option increases, and converting instruments are added to the post-change denominator.
How to Use This Calculator
- Enter the owner shares for the person or group being analyzed.
- Add other common shares, preferred shares, and existing option pool shares.
- Enter new investor shares, new option shares, or converting instrument shares.
- Add valuation and investment figures to compare share-based and value-based ownership.
- Choose whether existing options should be included in the diluted base.
- Press the calculate button to view results above the form.
- Use the CSV or PDF button to save the report.
Example Data Table
| Scenario |
Owner Shares |
Other Shares |
New Shares |
Total Post Shares |
Owner Percentage |
| Seed round |
250,000 |
750,000 |
120,000 |
1,120,000 |
22.32% |
| Option expansion |
250,000 |
750,000 |
170,000 |
1,170,000 |
21.37% |
| Note conversion |
250,000 |
750,000 |
200,000 |
1,200,000 |
20.83% |
Understanding Ownership Percentage
Ownership percentage shows how much of an entity belongs to one holder. It is a simple ratio, but it carries major meaning. It affects voting power, payout rights, dilution risk, and negotiation strength. A founder with 40 percent owns two fifths of the fully diluted base. After new shares are issued, that stake can fall even when the founder sells nothing.
Why Dilution Matters
Dilution happens when the total share count grows. New investor shares, option pool increases, and converted notes all add to the denominator. The holder keeps the same shares, yet each share represents a smaller fraction. This is why early planning matters. A small option pool change can move ownership by several points.
Statistical View
This tool also treats the cap table as a distribution. It calculates concentration using the Herfindahl index. A high value means ownership is clustered in fewer groups. A lower value means ownership is spread across more groups. The mean and standard deviation show how balanced the cap table appears.
Planning Uses
Use the results before a funding round, grant approval, partnership split, or buyout discussion. Enter current shares first. Then add new shares from financing or compensation. Review pre-round ownership, post-round ownership, absolute dilution, and relative dilution. Compare the direct share result with the valuation result. A large gap can show that the entered shares do not match the implied round price.
Interpreting Results
Post-money ownership is usually the most important number. It shows the stake after all selected changes. The required grant estimate helps when a holder wants a target percentage. The projected value section connects ownership to a possible future exit value. It is not a promise. It is a scenario model.
Good Practice
Keep records consistent. Use the same share class basis for every input. Fully diluted views usually include options and convertibles. Issued-share views may exclude them. Pick the view that matches your agreement. Then use the same view in every comparison.
For important transactions, confirm the numbers with formal documents. Share counts can change through vesting, repurchases, splits, warrants, and liquidation preferences. The model supports planning, but signed agreements control final rights and duties.
FAQs
1. What is ownership percentage?
Ownership percentage is the holder’s shares divided by the total shares in the chosen base. It shows the holder’s stake after considering the selected share classes.
2. What does fully diluted ownership mean?
Fully diluted ownership includes shares that may exist after options, warrants, convertibles, or similar instruments are counted. It gives a broader ownership view.
3. Why does ownership decrease after new shares?
Ownership decreases because the denominator grows. The holder may keep the same shares, but those shares represent a smaller part of the total.
4. What is dilution in percentage points?
It is the difference between old ownership and new ownership. For example, moving from 30 percent to 24 percent equals 6 percentage points.
5. What is relative dilution?
Relative dilution compares the ownership loss to the original percentage. It helps show how large the reduction is against the starting stake.
6. Why compare share ownership with valuation ownership?
The comparison helps check consistency. If the share-based investor percentage differs greatly from the valuation result, the entered share amount may need review.
7. What does HHI concentration mean?
HHI measures how concentrated ownership is. A higher score means fewer groups hold larger stakes. A lower score means ownership is more spread out.
8. Is this calculator legal advice?
No. It is a planning tool. Always review final ownership, voting rights, and payout terms with qualified legal and financial professionals.