Valuation and Dilution Explained: The Math Every Founder Should Be Able to Do in Their Head

Every founder learns the mechanics of valuation and dilution the hard way: by signing their first round, then a year later, doing the maths and discovering they own less than they thought. This article is the version of that learning written down in advance.

The two valuation numbers

When investors talk about valuation, two numbers matter:

• Pre-money valuation. What the company is worth before the new money goes in.
• Post-money valuation. What the company is worth after. Post-money = pre-money + amount raised.

Example: pre-money $20m, raising $5m. Post-money = $25m. The new investors collectively own $5m / $25m = 20%.

Founders sometimes hear "$25m valuation" and get excited, only to learn it was post-money — meaning the actual price of their company was $20m before the round. Always clarify which one is being quoted. Most US negotiations refer to pre-money; most SAFE caps are now post-money by default.

How dilution works

When new shares are issued, every existing shareholder owns a smaller percentage of the company.

A simple example. Say founders own 100% of a company. They issue new shares to investors equal to 25% of the post-issuance total. After the round:

• Founders: 75%
• New investors: 25%

The founders' percentage dropped, but their shares didn't change. The total share count went up.

That's the basic mechanic. The complications come from option pools, multiple rounds, and conversion of SAFEs.

The option pool problem

Almost every priced round either creates a new option pool or expands an existing one — and the new pool comes out of the pre-money valuation. This means founders take the dilution from the pool, not investors.

Example:

• Pre-money: $20m
• Round size: $5m
• New option pool: 10% post-money

The investors' demand is essentially: "post-money, your option pool should be 10%, your investors 20%, and the rest is yours". To achieve that, the option pool gets created out of the pre-money. The math:

• Post-money $25m: investors take 20% ($5m), pool is 10% ($2.5m), founders + existing 70% ($17.5m).
• The pool of $2.5m comes out of what was previously "founders + existing" — they go from $20m → $17.5m.

So the founders aren't diluted "by the round" — they're diluted by the round plus the option pool. The effective dilution from a $5m round at $20m pre-money with a 10% post-money pool is not 20%; it's roughly 30%.

Negotiating the option pool size is, therefore, real money. We cover the negotiation in what is a term sheet.

SAFE conversion and dilution

If you've raised SAFEs before your priced round, those SAFEs convert into shares as part of the priced round, with their own dilutive effect.

Example: pre-priced-round, you've raised $1.5m of SAFEs at a $10m cap.

When you raise your priced round at, say, $20m pre-money, the SAFE investors convert at $10m equivalent (their cap). They get more shares per dollar than the new round investors.

After conversion:

• SAFE investors collectively get ~13% (more if their cap was lower).
• New round investors get their negotiated stake.
• Founders are diluted by both.

The aggregate effect is often higher than founders modelled when they signed the SAFEs. Use a SAFE conversion model — Carta provides one — before stacking SAFEs.

Multi-round dilution

Each round dilutes you. The cumulative effect over multiple rounds is what determines what you own at exit.

A typical venture-backed founder's ownership trajectory:

• After founding: 100%
• After pre-seed (15% diluted): 85%
• After seed (20% diluted): 68%
• After Series A (20% diluted): 54%
• After Series B (18% diluted): 44%
• After Series C (15% diluted): 38%
• After Series D + IPO (10% combined): 34%

Notice: by Series A, the founders typically own around half the company. By Series D, perhaps a third. Some founders end IPO with much less; some with more, depending on rounds taken and valuations.

This is why valuation matters at every round. Every percentage you give up early compounds.

The valuation-vs-structure trade-off

Founders often optimise valuation aggressively without considering structure. This is sometimes a mistake.

A higher valuation with worse structural terms can be worse than a lower valuation with clean terms. Examples of bad structural trades:

• Higher valuation but participating preferred (investors get their money back and their share of upside).
• Higher valuation but a 20% post-money option pool out of pre-money (you eat all the pool dilution).
• Higher valuation but multiple liquidation preference (rare at seed but seen).

Always evaluate a term sheet on the combined economics, not just the headline number.

How much dilution should you expect per round?

Rough benchmarks (US, 2026):

• Pre-seed: 10–20% to investors. Plus 5–10% option pool top-up.
• Seed: 15–25% to new investors. Plus 5–10% option pool top-up.
• Series A: 15–25%. Plus 5–10% pool top-up.
• Series B: 15–20%. Often smaller pool top-ups.
• Series C+: 10–18%.

Adding it all up: by Series B, founders have typically given up 40–55% of the company. The exact number depends on round sizes, valuations, and pool sizes.

A worked example: cumulative dilution

Founders start at 100%. They raise:

1. Pre-seed: $1m on a SAFE at $5m post-money cap. Equivalent to ~17% dilution at conversion.
2. Seed: $4m at $20m post-money. 20% dilution to new investors. Plus 5% pool top-up.
3. Series A: $12m at $60m post-money. 20% to new investors. Plus 5% pool top-up.

After all three rounds, founders own:

• After pre-seed SAFE conversion: 83%
• After seed (20% to investors + 5% pool from pre-money): 60–62%
• After Series A (20% to investors + 5% pool from pre-money): 44–46%

By Series A, founders have ~45% — typical for a well-run venture trajectory.

Dilution after employee equity

The numbers above are founder shares. Some founders also factor in employee equity that hasn't yet been granted (the unallocated option pool). When granted, that pool dilutes the founders further as employees vest.

Plan for total founder ownership at IPO of around 20–35% after a typical multi-round venture path. Higher if you're capital-efficient; lower if you raised late or large rounds.

What this means for negotiating

Three priorities when negotiating valuation and structure:

1. Don't sign a structure trade you don't understand. A 30% higher pre-money is sometimes worse than a clean term sheet at lower pre-money.
2. Negotiate the option pool size by reference to your real hiring plan, not "what's market".
3. Model your dilution end-to-end before each round — not just this round, but the next two.

The math isn't optional. Every founder who's been through it learns to do it in their head. The earlier you learn it, the better the rounds you sign.