Dilution Calculator

See how much existing ownership is diluted by a new round, including any new option pool.

About Dilution Calculator

Dilution is multiplicative, not additive: your stake is scaled down by whatever share of the company new investors and the option pool take. Value can still rise even as ownership falls, provided the valuation rises by more than the dilution. Founders track percentage points but investors track value — comparing the before and after stake values is what shows whether a round was worth the dilution.

Formula

Dilution

Ownership after = current ownership × (100% − investor share − new option pool)

investor share: Investment divided by post-money valuation
relative dilution: Points lost as a share of what you held before

Worked example

With the default values below, Dilution Calculator returns Ownership After the Round of 16.731%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Your current ownershipaccepts 0–100 %: 25 %
Pre-money valuationminimum 0.01: 10,000,000
New investmentminimum 0: 3,000,000
New option pool createdaccepts 0–100 %: 10 %

Results

Ownership After the Round: 16.731%
Percentage Points Lost: 8.269%
Relative Dilution of Your Stake: 33.08%
Value of Your Stake Before: $2,500,000
Value of Your Stake After: $2,175,000

Step by step

1Values used
2Dilution
3Ownership After the Round= 16.731
4Percentage Points Lost= 8.269
5Relative Dilution of Your Stake= 33.08
6Value of Your Stake Before= 2,500,000
7Value of Your Stake After= 2,175,000

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This is an estimate for general information and not professional financial, tax or legal advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Dilution calculated?

Ownership after = current ownership × (100% − investor share − new option pool) Dilution is multiplicative, not additive: your stake is scaled down by whatever share of the company new investors and the option pool take. Value can still rise even as ownership falls, provided the valuation rises by more than the dilution.

Why does Dilution matter?

Founders track percentage points but investors track value — comparing the before and after stake values is what shows whether a round was worth the dilution.

What values do I need to enter?

This calculator takes 4 inputs: Your current ownership, Pre-money valuation, New investment, New option pool created. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.