# Equity Dilution Calculator for Startups: Seed, Series A, Option Pool and SAFEs

> Work out how much of the company founders keep after a round: pre-money valuation, amount raised, option pool top-up and SAFE conversion. Typical rounds sold 18–19% at seed and Series A in 2025.

Resources · 31 October 2026 · by Giorgio Fenancio · https://privateequitylist.com/intelligence/dilution-calculator

**Key takeaways**

- **Equity dilution in one line:** new investors own the amount raised divided by the post-money valuation. Raise $2M at an $8M pre-money valuation and they own 20%, so founders go from 100% to 80%.
- **Typical dilution:** in Carta's data for January 2021 to May 2025, the typical seed round sold 19% of the company in 2025, Series A 18%, Series B 15% and Series C 9.6%.
- **Option pool:** a pool topped up before the round comes out of the existing holders only. In our Series A example founders end at 50.6% that way, against 51.7% with the top-up after the round.
- **SAFEs:** a SAFE converts at the lower of its cap price and the discounted round price. A $1M SAFE with a $10M cap takes 7.6% of the company at a $15M pre-money seed.
- **Dilution is not a loss by itself:** founders own a smaller share of a company that is worth more. It costs them only when the price is too low or the round bigger than needed.

**Equity dilution calculator** (interactive on the page)

- Post-money valuation = pre-money + new money. Example: $40M + $10M = $50M; price per share $3.61
- New investors' stake = new shares ÷ shares after the round = 20.0%
- Founders: 70.0% before, 50.6% after (option pool 15.0% after the round), a dilution of 27.8%
- SAFEs and notes convert at the lower of the cap price (cap ÷ shares before the round) and the round price less the discount

- **19%**: typical seed round (share sold, 2025)
- **18%**: typical Series A (share sold, 2025)
- **15%**: typical Series B (share sold, 2025)
- **9.6%**: typical Series C (share sold, 2025)

**Source:** Carta data on 12,435 venture rounds from January 2021 to May 2025, in [SaaStr's analysis](https://www.saastr.com/the-dilution-non-story-why-12435-software-rounds-show-remarkably-little-has-changed/). Carta's own [2025 year-end review](https://carta.com/data/state-of-private-markets-q4-2025-full-report/) puts the typical round from seed to Series C at about 16% for the full year.

## What is equity dilution

**Equity dilution:** the drop in an owner's percentage when a company issues new shares. Founders keep the same number of shares, but there are more shares in total.\
**What causes it:** a new funding round, a SAFE or convertible note turning into shares, and new options added to the employee pool.\
**Fully diluted:** counts every share and option, including the unissued pool. Investors negotiate on this basis, so the calculator uses it too.\
**Value can still grow:** owning 80% of a $10M company is worth more than 100% of an $8M one, as long as the new money is put to work.

## Dilution formula

<div class="intel__tablewrap">
<table class="intel__table">
<thead><tr><th>What</th><th>Formula</th><th>Seed example</th></tr></thead>
<tbody>
<tr><td>Post-money valuation</td><td>Pre-money valuation + amount raised</td><td>$8M + $2M = $10M</td></tr>
<tr><td>New investors' stake</td><td>Amount raised ÷ post-money valuation</td><td>$2M ÷ $10M = 20%</td></tr>
<tr><td>Stake after the round</td><td>Stake before × (1 − new investors' stake)</td><td>100% × 0.8 = 80%</td></tr>
<tr><td>Dilution</td><td>1 − stake after ÷ stake before</td><td>1 − 80% ÷ 100% = 20%</td></tr>
<tr><td>Price per share</td><td>Pre-money valuation ÷ shares before the round</td><td>$8M ÷ 10,000,000 = $0.80</td></tr>
<tr><td>New shares</td><td>Amount raised ÷ price per share</td><td>$2M ÷ $0.80 = 2,500,000</td></tr>
</tbody>
</table>
</div>

**When the simple formula breaks:** an option pool top-up or a converting SAFE adds shares before the new money comes in, so founders lose more than the investors' stake. The examples below show by how much.

## Example 1: seed round, no option pool

**The setup:** two founders own 100% of 10,000,000 shares. They raise $2M at an $8M pre-money valuation.\
**The price:** $8M ÷ 10,000,000 shares = $0.80 a share. The investors buy 2,500,000 new shares for $2M.\
**The result:** 12,500,000 shares in total. Investors own 20%, founders 80%, a dilution of 20%.

## Example 2: Series A with an option pool top-up

**The setup:** founders own 70%, seed investors 20% and the option pool 10%. The company raises $10M at a $40M pre-money valuation, and the lead investor asks for a 15% pool after the round.\
**The option pool shuffle:** when the extra pool is counted in the pre-money valuation, only the existing holders pay for it. The price falls to $3.61 a share.

<div class="intel__tablewrap">
<table class="intel__table">
<thead><tr><th>Holder</th><th>Before</th><th>After, pool topped up before the round</th><th>After, pool topped up after the round</th></tr></thead>
<tbody>
<tr><td>Founders</td><td>70.0%</td><td>50.6%</td><td>51.7%</td></tr>
<tr><td>Seed investors</td><td>20.0%</td><td>14.4%</td><td>14.8%</td></tr>
<tr><td>Option pool</td><td>10.0%</td><td>15.0%</td><td>15.0%</td></tr>
<tr><td>Series A investors</td><td>0%</td><td>20.0%</td><td>18.5%</td></tr>
<tr><td>Price per share</td><td>–</td><td>$3.61</td><td>$4.00</td></tr>
</tbody>
</table>
</div>

**What it costs founders:** a little over 1 point of the company (51.7% against 50.6%). On a $50M post-money valuation that is roughly $590,000 of value.\
**What to negotiate:** the pool size, based on a hiring plan for the next 18–24 months, and whether the top-up sits before or after the round.

## Example 3: a SAFE converting at a priced seed

**The setup:** founders own 90% and the pool 10% of 10,000,000 shares. An earlier $1M SAFE has a $10M valuation cap and a 20% discount. Now the company raises $3M at a $15M pre-money valuation.\
**Two prices for the SAFE:** the cap price is $10M ÷ 10,000,000 = $1.00. The round price is $15M ÷ 11,000,000 shares = $1.36, so the discounted price is $1.09.\
**The lower price wins:** the SAFE converts at $1.00 into 1,000,000 shares. The pre-money valuation includes those shares, so the founders and the pool pay for them.

<div class="intel__tablewrap">
<table class="intel__table">
<thead><tr><th>Holder</th><th>Shares</th><th>Before</th><th>After</th></tr></thead>
<tbody>
<tr><td>Founders</td><td>9,000,000</td><td>90.0%</td><td>68.2%</td></tr>
<tr><td>Option pool</td><td>1,000,000</td><td>10.0%</td><td>7.6%</td></tr>
<tr><td>SAFE holder</td><td>1,000,000</td><td>–</td><td>7.6%</td></tr>
<tr><td>Seed investors</td><td>2,200,000</td><td>–</td><td>16.7%</td></tr>
<tr><td>Total</td><td>13,200,000</td><td>100%</td><td>100%</td></tr>
</tbody>
</table>
</div>

**The result:** founders give up 24.2% of their stake in one round, though the new investors hold only 16.7%. Several SAFEs on top of each other add up quickly.\
**Post-money SAFEs:** Y Combinator's [standard SAFE](https://www.ycombinator.com/documents) converts a little differently: before the new money, the holder owns the amount divided by the cap, 10% here instead of 9.1%. Check your own documents for the exact terms.

## Typical dilution by round

**Share of the company sold in a typical round**

| | 2021 | 2025 |
|---|---:|---:|
| Seed | 20% | 19% |
| Series A | 20% | 18% |
| Series B | 16% | 15% |
| Series C | 12.5% | 9.6% |

Source: Carta data on 12,435 rounds, via SaaStr

**Stable for years:** seed and Series A rounds have sold about a fifth of the company since 2021. Only Series C moved much, mostly because rounds got smaller.\
**The 2025 picture:** Carta's year-end review shows the typical round from seed to Series C falling from about 18% to 16% over 2025.\
**What it adds up to:** at 19% and 18%, two rounds leave founders with about 66% of the stake they started with, before any pool top-ups or SAFEs.

## How to limit dilution

**Raise what the plan needs:** every extra million at the same price is more of the company sold.\
**Size the pool from the hiring plan:** ask the investor to agree on the hires the pool must cover, and keep it no bigger than that.\
**Ask for a post-money top-up:** in Example 2 it saved founders over 1 point of the company.\
**Count your SAFEs:** model every SAFE and note in the calculator before the priced round, not after.\
**Mix in debt:** a loan next to the round can extend runway with little dilution. Lenders are in our guide to [venture debt lenders and funds](https://privateequitylist.com/intelligence/venture-debt-lenders-and-funds).\
**Raise after a milestone:** a higher pre-money valuation sells less of the company for the same money.

## Find seed and Series A investors

**Seed investors:** Private Equity List's [seed investor list](https://privateequitylist.com/investors/seed) can be filtered by sector, country and cheque size.\
**Series A investors:** the same for the [Series A investor list](https://privateequitylist.com/investors/series-a).\
**Funds with fresh money:** the [new funds tracker](https://privateequitylist.com/new-vc-funds) lists venture funds as they close, and those are the ones writing cheques now.\
**Other calculators:** the [cost of equity calculator](https://privateequitylist.com/intelligence/cost-of-equity-calculator) works out the return investors require from a company's shares.

## Data and methodology

**Shares:** everything is counted on a fully diluted basis, including the whole option pool. The share count before the round only changes the price per share, not the percentages.\
**Option pool:** a top-up before the round counts in the pre-money share count, so it dilutes only the existing holders. A top-up after the round dilutes the new investors too.\
**SAFEs and notes:** they convert at the lowest of three prices: the cap divided by the shares before the round, the round price less the discount, and the round price. The converted shares count in the pre-money share count.\
**Solving the round:** the pool and the SAFE depend on the round price, and the price depends on them, so the calculator repeats the calculation until the numbers stop changing.\
**Typical dilution:** Carta's figures cover 12,435 rounds from January 2021 to May 2025, as summarised by SaaStr, plus Carta's 2025 year-end review. Figures are rounded to one decimal.

## FAQ

### How do you calculate equity dilution?

Divide the amount raised by the post-money valuation, which is the pre-money valuation plus the new money: that is the new investors' stake. Every existing holder keeps their stake times one minus that. $2M at an $8M pre-money valuation gives investors 20% and takes founders from 100% to 80%. Option pool top-ups and converting SAFEs dilute founders further.

### How much dilution is normal in a seed round?

In Carta's data, the typical seed round sold 19% of the company in 2025, against 20% in 2021. Series A rounds sold 18% and Series B rounds 15%.

### What is the option pool shuffle?

Investors often ask for the option pool to be topped up before the round, inside the pre-money valuation. The new options then come out of the founders' and earlier investors' stakes only, and the price per share falls. In our Series A example it costs founders a little over 1 point of the company compared with a top-up after the round.

### How do SAFEs dilute founders?

A SAFE turns into shares at the next priced round, at the lower of its cap price and the discounted round price. Those shares usually count in the pre-money valuation, so founders and earlier holders pay for them. In our example a $1M SAFE with a $10M cap ends up with 7.6% after a $3M seed at a $15M pre-money valuation.

### Do founders lose money when they are diluted?

Not necessarily. Their percentage shrinks, but the company is worth more after the round: 80% of a $10M company is worth more than 100% of an $8M one. Dilution costs founders when they sell more of the company than they need, or at too low a price.