Employee Equity Dilution Calculator
Equity dilution is one of the least understood yet most consequential aspects of startup ownership, affecting founders, early employees, and investors every time new shares are issued. When a company raises a funding round or expands its employee stock option pool, it creates new shares — and because the total pie grows while your share count stays the same, your ownership percentage falls even though the number of shares you hold is unchanged. Understanding dilution is essential for negotiating offers, evaluating the real value of your equity, and modeling what your stake could be worth at exit. This calculator shows your ownership before and after a new issuance and the exact percentage points you give up. Enter your shares and the new issuance to see precisely how dilution reshapes your slice of the company.
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Results
Results update live as you type. Estimates only — not financial, tax, or investment advice.
The Formula
Ownership After = Shares Owned ÷ (Total Shares + Newly Issued Shares) × 100
Understanding the Employee Equity Dilution Calculator
Dilution is not inherently bad — it is the price of the capital and talent that grow the company. The goal is not to avoid dilution but to ensure that each round makes your smaller slice worth more than your previous larger slice of a less valuable company. A founder diluted from 100% to 20% across several rounds can be vastly wealthier if those rounds took the company from an idea to a billion-dollar valuation. What matters is the value of your stake, not the percentage in isolation.
The employee option pool is a frequently overlooked source of dilution. Investors often require a pool to be created or topped up before a round, and that pool is typically carved out of the pre-money valuation — meaning existing shareholders, not the new investor, bear the dilution. When evaluating a job offer or a term sheet, always ask about the fully diluted share count, which includes the option pool and any convertible instruments, because ownership calculated on basic shares alone overstates what you actually hold.
Frequently Asked Questions
Is equity dilution always bad?
No. Dilution is the natural cost of raising capital and funding an option pool that grow the company. A smaller percentage of a much more valuable company is usually worth far more than a larger percentage of a smaller one. Focus on the value of your stake, not the percentage alone.
How does an option pool cause dilution?
When a company creates or expands an employee option pool, it issues new shares reserved for future hires, increasing the total share count and diluting existing holders. Investors often require the pool to be added before their round, out of the pre-money valuation, so existing shareholders — not the new investor — absorb that dilution.
What is fully diluted share count?
Fully diluted share count includes all outstanding shares plus every share that could be created from options, warrants, and convertible instruments. Ownership percentages should be calculated on the fully diluted count, because using basic shares alone overstates your true stake in the company.