Dilution is the decrease in an existing shareholder's ownership percentage when a company issues new shares. It happens during funding rounds, option pool expansions, SAFE or note conversions, and warrant issuances. Your share count does not change; the total shares outstanding grows, so your slice of the pie gets smaller. The math is mechanical; the emotional impact is not.
The per-round math (2025 benchmarks, Carta and PitchBook data):
| Round | Typical dilution | Typical new shares | What's diluting you |
|---|---|---|---|
| Pre-seed (SAFE) | 10-15% on conversion | $250K-$1M at $5M-$10M cap | SAFE conversion at priced round |
| Priced seed | 18-25% | $2M-$5M at $8M-$20M pre | New shares + option pool refresh |
| Series A | 17-22% | $8M-$15M at $30M-$80M pre | New shares + ... |