Share Dilution Calculator: a practical guide
How would new company shares change my ownership?
Model an unchanged holding when a company issues additional shares.
By VolatileShares · Example version 1 · Updated . Hypothetical inputs, not financial recommendations or live company data.
A worked example, in plain English
The idea in 10 seconds: More slices of the same ownership pie make your unchanged slice a smaller percentage.
Same shares. A different slice of the pie.
Ownership dilution is not the same as a share-price fall. Cash raised is not valued here.
- Relative ownership reduction
- 16.67%
- Ownership before issuance
- 0.001%
- Ownership after issuance
- 0.000833%
Walk me through the full calculation
Issuing 200,000 shares increases the entered total from 1,000,000 to 1,200,000. If your 10 shares stay unchanged, your ownership moves from 0.001% to 0.000833%.
Each existing share represents 16.67% less of the company relative to its previous ownership fraction. This is not a 16.67% predicted stock-price drop. Cash raised and how it is used can change the economic picture; conversions, buybacks and your participation would change this scenario.
Inputs used for this example
These are the calculator's example defaults, not suggested amounts or rates. Market calculators initially display USD. Change currency in the toolbar without creating a personal profile. Under optional Location & display settings, choose an example country for its currency and available historical CPI. Review any example household size and rent assumption before explicitly applying local assumptions: matching unedited budget/inflation fields change, while edited or restored inputs are kept. Lifestyle budgets are fictional examples, not measured national averages. Local tax, pension and borrowing links are guidance, not personal calculations. Switching currency alone does not change percentages, ages or share counts.
- Company shares before the new issue
- 1,000,000
- New company shares to add
- 200,000
- Shares you own
- 10
Work backwards from your goal
How many new shares would produce this ownership reduction?
Start with a relative ownership reduction to find the new share count.
Choose Work backwards, enter your target and the few essential inputs, then choose Calculate my goal. The answer is checked with the same forward calculation and applied in one step. Example assumptions are disclosed under More options. Expand Calculation details & tools only if you want more detail. Impossible or out-of-range goals show an error instead of invented numbers. Long numbers display commas while editing; calculations and saved snapshots keep the original precision.
Return to the interactive calculator above →How the calculation works
New total = existing shares outstanding + newly issued shares. Ownership = owned shares / shares outstanding x 100. Relative ownership reduction = new shares / new total x 100.
What this cannot tell you
Simple issuance scenario: you do not participate in the new issue, and there are no buybacks, conversions or other share changes. Use the same share class and consistent fully diluted or basic share counts. Does not estimate a stock-price decline or the value of cash raised.
Changing an assumption changes the example, not the future. Verify source dates and actual product, tax and lending terms before relying on any result. These tools do not replace appropriately qualified advice.
25% more shares means 20% less ownership per old share
Increasing 100 shares outstanding to 125 makes each unchanged old share represent 1 / 125 instead of 1 / 100 of the company: a 20% relative reduction. This is not a predicted 20% stock-price fall; proceeds and their use matter too.
Illustrative arithmetic, not market evidence or a promise of returns.
Keep a useful starting point
In the interactive calculator, compare different assumptions or explicitly save a named snapshot to My browser notebook. Saving is optional and browser-only, not an account or cloud backup. Revisit it on the same browser profile; restoring never refreshes prices or assumptions.