Fully Diluted Shares
The total number of company shares that would be outstanding if all convertible securities — options, warrants, convertible notes, and RSUs — were exercised or converted.
What Are Fully Diluted Shares?
Fully diluted shares represent the maximum number of common shares that would exist if every convertible instrument were exercised or converted. This includes shares currently outstanding plus shares underlying all stock options (vested and unvested), restricted stock units, warrants, convertible notes, convertible preferred stock, and any other securities that could convert into common stock. The fully diluted share count gives you the most comprehensive picture of total potential ownership and is the denominator you should use when calculating your ownership percentage.
Companies typically report both basic shares outstanding (shares actually issued) and fully diluted shares. For startup employees evaluating their equity, the fully diluted number is almost always the relevant figure.
How Fully Diluted Shares Are Calculated
Components
A typical fully diluted share count includes:
| Component | Description |
|---|---|
| Common shares outstanding | Shares already issued to founders, employees, and investors who converted |
| Preferred shares (as-converted) | Preferred shares converted to common at their conversion ratio |
| Outstanding stock options | All granted options, both vested and unvested |
| Ungranted option pool | Shares reserved for future grants but not yet allocated |
| RSUs | Restricted stock units, both vested (unsettled) and unvested |
| Warrants | Rights to purchase shares, often held by lenders or early investors |
| Convertible notes | Debt that converts to equity, typically at the next priced round |
| Other convertible securities | SAFEs, convertible preferred, etc. |
Example Calculation
- Common shares outstanding: 5,000,000
- Preferred shares (as-converted): 3,000,000
- Outstanding options (vested + unvested): 1,500,000
- Ungranted option pool: 500,000
- Warrants: 200,000
- Convertible notes (estimated conversion): 300,000
- Fully diluted shares: 10,500,000
If you hold 50,000 options, your fully diluted ownership is 50,000 / 10,500,000 = approximately 0.48%.
Why the Option Pool Matters
The ungranted option pool is often included in fully diluted share counts because those shares are reserved and will likely be granted. However, some calculations exclude the ungranted pool, which makes your ownership percentage look slightly better. Always ask whether the share count includes the ungranted pool to ensure you are comparing apples to apples.
Practical Implications for Startup Employees
Understanding Your Ownership Percentage
When a company tells you that you are being granted 50,000 shares, the number is meaningless without knowing the fully diluted share count. 50,000 shares out of 10 million fully diluted shares (0.5%) is very different from 50,000 out of 100 million (0.05%). Always ask for the fully diluted share count when evaluating an equity offer.
How Dilution Erodes Ownership
Each time the company raises a new round of funding, issues new stock options, or converts notes into equity, the fully diluted share count increases. If you hold 50,000 shares and the fully diluted count goes from 10 million to 15 million after a funding round, your ownership drops from 0.5% to 0.33% — even though you still hold the same number of shares. This is dilution, and it is the most common way that employee ownership percentages decrease over time.
Modeling Exit Value
To estimate the value of your equity at a potential exit, multiply your shares by the per-share price. But the per-share price depends on the fully diluted share count and the company's total valuation:
Per-share price = Company Valuation / Fully Diluted Shares
At a $500 million valuation with 10.5 million fully diluted shares, each share is worth approximately $47.62. Your 50,000 shares would be worth approximately $2.38 million before taxes and liquidation preferences.
Cap Table vs. Fully Diluted
A cap table lists all equity holders and their holdings. The fully diluted share count is derived from the cap table by summing all actual and potential common shares. When reviewing your company's cap table, look for the fully diluted total at the bottom — this is the number that determines your real ownership.
How It Relates to Exercising Stock Options
When deciding whether to exercise stock options, the fully diluted share count helps you estimate the potential value of your shares. If you know the company's latest 409A valuation and the fully diluted share count, you can calculate the current fair market value per share. Comparing this to your strike price tells you the current spread, which drives your tax liability at exercise. Additionally, understanding the fully diluted count helps you model future dilution from anticipated funding rounds, so you can make a more informed decision about whether exercising now (at a known dilution level) is preferable to waiting (when further dilution may reduce your per-share value).