Stock Dilution Calculator
See how a new share issue shrinks your ownership percentage and the value of your stake.
What this calculator does
The Stock Dilution Calculator estimates your result instantly from the values you enter, using standard investing & wealth formulas. See how a new share issue shrinks your ownership percentage and the value of your stake. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate for planning rather than financial advice.
Result
About Stock Dilution Calculator
The Stock Dilution Calculator shows how your ownership percentage shrinks when a company issues new shares. It divides the shares you own by the total shares before the raise to get your starting stake, then divides the same holding by the enlarged share count to get your diluted stake.
Dilution matters whenever a company raises capital by issuing new equity: your share count stays the same, but each share represents a smaller slice of a bigger pie. Seeing the before-and-after percentages makes the effect of a funding round or option grant concrete. The calculator applies both divisions directly to the figures you enter.
Enter the shares you own, the total shares before, and the new shares issued, press Calculate, and read your ownership before and after dilution.
Formula & Mathematical Calculation
Ownership Before (%) = ( Shares You Own ÷ Total Shares Before ) × 100
Ownership After (%) = ( Shares You Own ÷ ( Total Shares Before + New Shares Issued ) ) × 100
Calculation Example
Owning 10,000 of 100,000 total shares is a 10% stake. After 50,000 new shares are issued, the same holding is 10,000 ÷ 150,000 = 6.6667%.
Key Benefits
- Shows ownership percentage before and after new shares are issued.
- Makes the dilution from a funding round or option grant concrete.
- Keeps your share count fixed while the total share base grows.
- Requires total shares above zero, avoiding a divide-by-zero result.
How to Use this Calculator
-
Enter the shares you own
Type your current share count in the Shares You Own field, for example 10000. -
Enter the total shares before
Type the total shares outstanding before the raise in the Total Shares Before field, for example 100000. -
Enter the new shares issued
Type the number of new shares being issued in the New Shares Issued field, for example 50000. -
Press Calculate
The tool divides your holding by the old total for the before figure and by the enlarged total for the after figure.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Rates and contributions are assumed to stay constant for the whole period unless the form asks for them separately.
- Results use standard financial formulas and ignore fees, penalties and promotional terms that are not entered above.
- Inflation, tax changes and market volatility are not modelled unless a field for them is provided.
- Amounts are unit-agnostic: results are returned in the same currency you enter.
What it does not cover
- Stock Dilution Calculator produces estimates for education and planning, not a quote, offer or professional advice.
- Real-world outcomes differ when fees, taxes, rounding rules or provider-specific terms apply.
- Local regulations and tax rules vary by country and change over time; verify current rules for your jurisdiction.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For decisions with lasting financial impact, confirm the numbers with a qualified professional.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.
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