What is Dilution?
Dilution is the reduction in ownership percentage that occurs when new shares are issued. When your company raises money or grants equity, new shares are created, and everyone's percentage ownership decreases.
Dilution is not inherently bad. If new investment grows the company's value, you can own a smaller percentage of something worth much more. 10% of $100M is better than 50% of $1M.
Why Dilution Matters
Excessive dilution erodes founder motivation and control. If you own less than 10% after several rounds, your economic incentive is weakened. Institutional investors typically want founders to retain meaningful ownership.
Each round of funding typically dilutes existing shareholders by 15-25%. After multiple rounds, early shareholders can be significantly diluted, which is why ownership percentage at exit matters more than percentage after each round.
Managing Dilution
Raise only what you need. Grow revenue to command higher valuations. Negotiate pro-rata rights to maintain percentage. Understand the cumulative effect across multiple rounds.
How to Calculate Dilution Step by Step
Step 1: Know your current ownership. Before the round, you own X% of the company.
- Your current ownership: 70% (after co-founder split and early option grants)
Step 2: Calculate how much the round dilutes. New Investor % = Investment ÷ Post-Money Valuation.
- Investment: $3,000,000
- Pre-money: $12,000,000
- Post-money: $15,000,000
- New investor ownership: $3M ÷ $15M = 20%
Step 3: Calculate your new ownership. Your Post-Round % = Pre-Round % × (1 - New Investor %).
- Your new ownership: 70% × (1 - 0.20) = 56%
Step 4: Model cumulative dilution across rounds.
| Round | Raise | Pre-Money | Your Ownership |
|---|---|---|---|
| Founding | — | — | 70% |
| Seed | $3M | $12M | 56% |
| Series A | $8M | $32M | 45% |
| Option pool refresh (10%) | — | — | 40% |
After two rounds and an option pool refresh, you've gone from 70% to 40%. This is normal, but understand the trajectory before each raise.
Common mistakes founders make:
- Not modeling cumulative dilution before raising (each round compounds)
- Ignoring option pool expansions (often 10-15% carved out before each round, diluting founders)
- Raising more than needed at a low valuation (maximizes dilution)
- Not using the startup equity dilution calculator to model scenarios before negotiating
Formula
Dilution % = (New Shares Issued) ÷ (Total Shares After Issuance) × 100
New Ownership % = Old Shares ÷ (Old Total Shares + New Shares Issued)
Example
Before Series A:
- You own: 60% of 10M shares = 6M shares
Series A terms:
- New shares issued: 2.5M
- Total shares after: 12.5M
Your ownership after: 6M ÷ 12.5M = 48%
Dilution = 60% - 48% = 12 percentage points
You still own 6M shares, but they represent a smaller piece of a larger pie.