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DILUTION / CAP TABLE

Startup dilution and cap table calculator

See how founders' ownership changes through seed, Series A and Series B rounds, including the option pool top-up investors usually ask for before each round.

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01Before the first round

02Seed

Unissued pool as a share of the company after the round; 0 for no top-up.

03Series A

Unissued pool as a share of the company after the round; 0 for no top-up.

04Series B

Leave at 0 to skip this round.

Unissued pool as a share of the company after the round; 0 for no top-up.

Founders' ownership after Series A

50.6%

worth $20,222,222 at a $40,000,000 post-money

Value of founders' shares
$20,222,222
All investors
39.4%
Option pool
10%
Post-money valuation
$40,000,000
  • Each round: the option pool is topped up first so it equals the target share of the company after the round (the 'option pool shuffle'), then new shares are issued at price = pre-money valuation ÷ fully diluted shares including the top-up. New investors own investment ÷ post-money valuation.
  • Because the pool top-up happens before the money comes in, it dilutes founders and earlier investors, not the new ones. Pool added: Seed 1,142,857 shares, Series A 439,560 shares.
  • Ownership is fully diluted: all shares, granted options and the unissued pool. SAFEs and notes converting in a round are not included here; the SAFE calculator handles them.

Founders' ownership after Series A: 50.6% worth $20,222,222 at a $40,000,000 post-money

Ownership after Series A
51%TAKE-HOME
  • Founders50.6%51%
  • Option pool10%10%
  • Seed investors14.4%14%
  • Series A investors25%25%

Ownership after each round

RoundPrice per sharePost-moneyFoundersOption poolSeed investorsSeries A investors
Seed$0.87$10,000,00070%10%20%—
Series A$2.53$40,000,00050.6%10%14.4%25%

50.6%

worth $20,222,222 at a $40,000,000 post-money

How it's calculated

Each priced round issues new shares to investors, so everyone who already owns shares ends up with a smaller percentage. New investors own their investment ÷ the post-money valuation (pre-money + investment). Investors usually also ask for the employee option pool to be topped up before their money comes in, so that the unissued pool is a set percentage of the company after the round. Because those new options are created in the pre-money, they dilute the founders and earlier investors, not the new investors; this is often called the option pool shuffle.

Y Combinator's SAFE user guide shows the same mechanics in its worked examples, where a Series A at a $15 million pre-money valuation includes an option pool increase sized to leave a 10% pool after the round.Y Combinator

The formula

For each round, with S fully diluted shares before it (including the existing unissued pool P) and k = post-money ÷ pre-money:

  1. Pool increase X = (target × k × S − P) ÷ (1 − target × k), so the unissued pool equals the target after the round
  2. Price per share = pre-money ÷ (S + X)
  3. New shares = investment ÷ price; investors own investment ÷ post-money
  4. Founders' ownership = founders' shares ÷ total shares after the round

Worked example

Founders with 8 million shares raise a $2 million seed at an $8 million pre-money with a 10% pool, then a $10 million Series A at a $30 million pre-money with the pool topped back up to 10%. Founders end up with 50.6%, worth $20,222,222 at the Series A price.

Seed and Series A with 10% poolsDILUTION / POST $40,000,000

Founders' ownership after Series A: 50.6% worth $20,222,222 at a $40,000,000 post-money

With no pool top-ups, founders keep 60% after the same two rounds.

Assumptions and limitations

  • Fully diluted ownership: all shares, granted options and the unissued pool count.
  • SAFEs and convertible notes converting in a round add further dilution; use the SAFE calculator for those.
  • Simple preferred terms. Liquidation preferences, anti-dilution adjustments and secondary sales are not modelled; they affect payouts rather than these percentages.
FAQ

Questions people ask

How do you calculate dilution from a funding round?

New investors' ownership after a round is the investment divided by the post-money valuation (pre-money plus investment). Everyone else's ownership is multiplied by one minus that share. Investing $2 million at an $8 million pre-money valuation buys 20%, so existing holders keep 80% of what they had, before any option pool increase.

What is the option pool shuffle?

Investors often ask for the option pool to be enlarged before their money comes in, so that the pool reaches a target, such as 10% of the company after the round. Because the new options are created in the pre-money, they dilute the existing shareholders but not the new investors, which effectively lowers the price founders receive.

What is the difference between pre-money and post-money valuation?

Pre-money valuation is what the company is worth before the new investment; post-money is pre-money plus the investment. The price per share is the pre-money valuation divided by the fully diluted shares before the money comes in, including any option pool increase.

How much do founders typically get diluted in each round?

It varies widely with the company and market. Each priced round commonly sells a meaningful minority stake to new investors, and option pool top-ups add to the dilution. Rather than relying on rules of thumb, model your planned rounds in the calculator to see founders' ownership after each one.

Does dilution mean founders lose value?

Not necessarily. Founders own a smaller share, but if the money raised increases the company's value enough, a smaller share of a bigger company can be worth more. The value of founders' shares after a round is their ownership times the post-money valuation.

Sources

  1. Y CombinatorPost-Money SAFE User Guide (conversion mechanics, Company Capitalization, Appendix II examples) · retrieved 2026-10-20

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How every figure is checked: methodology.