#943 · Startup Tool

Pre Seed Dilution Calculator

Calculate how much ownership founders and existing holders lose when new investor shares, SAFE conversions, and option pool expansion are added in a pre-seed round.

Calculator

Share dilution inputs
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How to use this calculator

  1. Enter current founder or existing common shares.
  2. Add new investor shares issued in the round.
  3. Include SAFE or convertible shares if they convert.
  4. Add new option pool shares created before or after the round.

What the result means

Dilution shows how much the old ownership base is reduced after new securities are issued. Large dilution at pre-seed can limit founder flexibility in later seed and Series A rounds.

Dilution = New shares issued ÷ Fully diluted shares. Founder ownership = Founder shares ÷ Fully diluted shares.

Share count mechanics vary by term sheet. Use this for directional cap table planning, then confirm with counsel or your cap table platform.

Example calculation

If founders own 1,000,000 shares and 350,000 new shares are added, fully diluted shares are 1,350,000 and founder ownership becomes 74.1%.

Tips for better results

  • Separate investor dilution from option pool dilution.
  • Model SAFE conversion before agreeing to a priced round.
  • Watch cumulative dilution across multiple rounds.
  • Use higher valuation or smaller round size to reduce dilution.

FAQ

How much dilution is normal in a pre-seed funding round?

Pre-seed dilution often falls between 10% and 25%, but it depends heavily on round size, valuation, and option pool changes.

How do SAFE notes increase founder dilution?

SAFE notes convert into shares, increasing the fully diluted share count and reducing founder percentage ownership.

Should option pool expansion be counted as dilution?

Yes. New option pool shares increase the fully diluted share count even if they are not granted immediately.

How can founders reduce dilution before seed funding?

Raise less capital, improve valuation, delay fundraising with revenue, or negotiate a smaller option pool increase.

What happens if pre-seed dilution is above 30 percent?

It can create future financing risk because founders may have too little ownership after seed and Series A rounds.

Startup decision table

MetricMeaning
DilutionNew shares as a percentage of fully diluted shares
SAFE ImpactDilution caused by converting notes or SAFEs
Option Pool ImpactDilution reserved for hiring

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