Equity dilution is the reduction in existing owners' ownership percentage when new shares are issued — through fundraising rounds, option exercises, convertible note conversions, or warrants. Dilution reduces per-share economic value and voting power unless proportionally offset by the value added.
Dilution occurs any time the total share count increases without existing owners buying proportional new shares. If you own 100 of 1,000 shares (10%), and the company issues 500 new shares to a new investor, you now own 100 of 1,500 shares (6.7%). Your percentage dropped from 10% to 6.7% — that's dilution. Dilution is not inherently bad. If the new capital raises the company's total value proportionally, each share may be worth more even though you own a smaller percentage. In venture-backed startups, founders routinely dilute from 100% to 20–30% over multiple rounds while their absolute dollar ownership grows dramatically. The key metric is not ownership percentage alone, but expected absolute value at exit. Sources of dilution: (1) equity fundraising rounds — investors receive new shares; (2) employee stock option plans (ESOPs) — options exercise creates new shares; (3) convertible note or SAFE conversions — deferred equity converts into shares, often with a discount or valuation cap; (4) warrant exercises — lenders or investors exercising warrants receive new shares. For SMBs considering venture or equity financing, dilution math should be modeled across scenarios. A $500K investment at a $2M pre-money valuation means selling 20% of the company ($500K / ($2M + $500K)). If future rounds further dilute, founding team should model the dilution waterfall to exit to understand expected returns.
Post-money ownership % = pre-money shares / (pre-money shares + new shares issued). New shares issued = investment amount / price per share. Example: $1M investment at $10/share = 100,000 new shares. If current share count is 900,000, post-money total = 1,000,000 shares. Existing owners dilute from 100% to 90%.
It depends entirely on the expected return on the deployed capital. Debt has fixed cost (interest rate, no dilution) but must be repaid. Equity has no repayment obligation but dilutes ownership. If the business expects high returns, debt is typically better — you keep 100% of the upside above the interest rate. If the business is early-stage with uncertain cash flows, equity avoids debt service pressure. This is the classic dilution vs. leverage tradeoff.
Anti-dilution provisions protect investors from dilution in down rounds (new funding at a lower valuation than the investor's entry). 'Broad-based weighted average' anti-dilution adjusts the investor's conversion price downward based on a weighted average of old and new share prices — less punitive to founders. 'Full ratchet' anti-dilution resets the conversion price to the new lower round price — very punitive to founders and rarely used today.