Every time a startup raises a funding round or grants employee stock options, existing shareholders own a smaller slice of a (hopefully) bigger pie. Understanding dilution mathematically — not just intuitively — is essential for founders negotiating term sheets and for early employees evaluating whether their equity grant is actually meaningful.

Pre-money valuation is what the company is worth immediately before new money comes in. Post-money is the valuation immediately after. If a company is valued at $8 million pre-money and raises $2 million, the post-money valuation is $10 million, and the new investor owns 2/10 = 20% of the company going forward.

A founder starts with 100% ownership (1,000,000 shares) of their company.

By the end of two funding rounds plus an option pool expansion, the founder's percentage ownership has dropped from 100% to roughly 57.6% — but critically, their absolute stake is now worth far more than 100% of the original, much smaller company was worth, assuming the company's valuation genuinely increased through these rounds. This is the central trade-off of dilution: smaller slice, hopefully much bigger pie.

Not necessarily — what matters is whether your absolute dollar value increased, not just your percentage. Going from 100% of a $1 million company ($1,000,000 in value) to 57.6% of a $25 million company (worth roughly $14.4 million on paper) is a dramatically better outcome despite the dilution, assuming that valuation increase reflects real, defensible business progress and not just inflated paper valuations that later get marked down.

A capitalization table (cap table) is the master ledger tracking every shareholder, how many shares (or options) they hold, and their resulting ownership percentage. As a company raises successive rounds, issues option grants, and potentially converts notes or SAFEs into equity, the cap table becomes increasingly complex — many seed-stage founders underestimate how much dilution accumulates from seemingly small option pool top-ups requested by each new investor.

A pro-rata right gives an existing investor the contractual option (not obligation) to invest additional money in future rounds, specifically to maintain their current ownership percentage rather than being passively diluted by new investors. Sophisticated angel and seed investors frequently negotiate for pro-rata rights as standard deal terms, since maintaining ownership in a company's later, larger rounds (once risk has been substantially de-risked) is often where the bulk of return is generated.

A subtle but important dynamic: new investors typically require the company to expand its employee option pool before their investment closes, which means the dilution from that pool expansion is effectively borne entirely by existing shareholders (founders and earlier investors), not by the new investor. This is a common, often underappreciated negotiation point — founders should always clarify whether a quoted valuation is "pre" or "post" option pool expansion, since the difference can meaningfully change effective dilution.