What is Equity Dilution?
Equity dilution happens when a company issues new shares, reducing every existing shareholder's ownership percentage. Your share count stays the same, but the total pie gets bigger, so your slice gets smaller.
Dilution is a normal part of startup growth. Every funding round, option pool increase, and convertible instrument conversion creates dilution. The question isn't whether you'll be diluted. It's how much.
Why Dilution Matters
A founder who starts at 100% might own 30-40% by Series A and 10-20% by Series C. Each round chips away at ownership. The goal is to make sure the value of your smaller percentage grows faster than the percentage shrinks.
Owning 15% of a $500M company ($75M) beats 80% of a $5M company ($4M). Dilution is worth it when it funds real growth.
Common Sources of Dilution
- Priced equity rounds (Series Seed, A, B, etc.)
- Option pool creation or expansion
- SAFE and convertible note conversions
- Warrant exercises
- Anti-dilution adjustments for prior investors
Formula
Dilution % = New Shares Issued ÷ (Existing Shares + New Shares Issued)
Post-Dilution Ownership = Original Ownership × (1 - Dilution %)
Or more directly:
Post-Dilution Ownership = Your Shares ÷ New Total Shares
Example
Founder owns 5,000,000 of 10,000,000 total shares (50%).
Series A investor buys 2,500,000 new shares.
- New total shares: 12,500,000
- Founder's new ownership: 5,000,000 ÷ 12,500,000 = 40%
- Dilution: 50% - 40% = 10 percentage points (or 20% relative dilution)
If the company also creates a 10% option pool (1,250,000 shares) from pre-money:
- New total shares: 13,750,000
- Founder's ownership: 5,000,000 ÷ 13,750,000 = 36.4%
The option pool added another 3.6 percentage points of dilution on top of the round itself.