Equity Dilution Explained: The Math Every Founder Needs to Understand

"Dilution isn't inherently bad. The question isn't whether you got diluted — you did. The question is whether you traded the right amount of ownership for the right amount of capital, at the right valuation, with the right terms."

⚠️ This post is for educational purposes only and is not legal or financial advice. Equity structures, dilution mechanics, and term sheet provisions are complex legal and financial instruments. Always work with a qualified startup attorney and financial advisor before making equity decisions.


The Math — Step by Step

Start: Founder owns 1,000,000 shares / 1,000,000 total = 100% Seed round: 250,000 new shares issued New total: 1,250,000 shares Founder new %: 1,000,000 / 1,250,000 = 80% Dilution: 20%

Key insight: share count didn't change. Percentage did. Dilution is always about percentage, not share count.

Value connection: if the seed round was at $4M pre-money ($1M for 20% = $5M post), the company needs to be worth more than $5M at next round for this to have been worth it. At $10M Series A, founder's 80% = $8M — better than 100% of a company stuck at $3M for lack of capital.


How Dilution Compounds (Illustrative)

Founding → 100%

  • Option pool → 88.9%
  • Seed → 76.2%
  • Series A → 61.5%
  • Series B → 50.0%

Each round dilutes all existing shareholders including previous investors. Every round must be justified by the value it creates.


The Option Pool Shuffle

Investors require an unallocated employee option pool (typically 10–20% post-money) exist before they invest. Key question: is it created from pre-money or post-money shares?

Standard (investor-friendly): pre-money. The pool is carved from existing shareholders (primarily founders) before investors come in — reducing the effective pre-money valuation founders actually receive.

Example: $8M pre-money / $2M invested / 20% post-money option pool. Those option pool shares are created pre-close, diluting founders before investors arrive. The headline "$8M pre-money" overstates what founders actually receive.

This isn't hidden — it's in the term sheet. But founders who don't model the full post-close cap table are regularly surprised. Always model it before evaluating any headline valuation.


Pro-Rata Rights

Give existing investors the right to maintain their ownership percentage in future rounds. Matters because: if existing investors exercise pro-rata, less allocation is available for new investors. If they don't exercise (negative signal) or compete with new investors for limited allocation, it complicates fundraising. Know who holds pro-rata rights and in what amounts before planning future rounds.


Anti-Dilution Provisions

⚠️ Anti-dilution provisions are negotiated legal terms — the specifics matter significantly. Not legal advice; work with a qualified startup attorney.

Protect investors if company raises in a down round.

Full ratchet: Investor's price adjusted to match the down round price exactly. Heavily investor-friendly. Rare in modern standard term sheets — push back hard if you see it.

Weighted average (standard): Adjustment calculated based on new price AND number of shares issued — proportional, much less punishing to existing shareholders. Two variants: broad-based (more founder-friendly) and narrow-based. Broad-based weighted average is current market standard.

Only triggers in a down round — but if it does, it can significantly increase investor ownership at founders' expense.


Practical Evaluation Framework for Any Term Sheet

  1. Model the full cap table post-closing (including option pool)
  2. Calculate the effective pre-money valuation (after option pool shuffle)
  3. Identify liquidation preference type: 1x non-participating (founder-friendly) vs. participating preferred (reduces founder payout in acquisition)
  4. Identify anti-dilution provision: broad-based weighted average = standard; full ratchet = negotiate hard
  5. Note pro-rata rights holders and amounts

Two term sheets with the same headline valuation can have materially different economics. Evaluate the whole package.


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