How to use this dilution calculator
- Set today's option pool. Founders own the rest of the company.
- Add each round in order. For a SAFE round, enter the amount raised and the post-money valuation cap. For a priced round, enter the amount raised, the pre-money valuation and the option pool the investors want afterwards.
- Read the projection: your ownership after every round, how much of your stake each round costs, and what that stake is worth at each valuation.
It starts with a typical path: a $750K pre-seed SAFE, a $3M seed round and a $10M Series A. Founders go from 90% to 47.1% while the paper value of their stake reaches $23.54M.
How equity dilution works
When a startup raises money, it issues new shares. You keep the same number of shares, but they become a smaller slice of a bigger total. In a priced round:
New investors' stake = amount raised ÷ post-money valuation
Your ownership after = your ownership before × (1 − new investors' stake − pool increase)
In the example, the seed investors buy $3M ÷ $15M = 20% of the company. The founders go from 81.0% to 62.3%, a 23.1% cut in their stake, because the option pool is topped up back to 10% at the same time.
The option pool shuffle
New investors usually want a bigger option pool for future hires, and they want it created before they invest, inside the pre-money valuation. The new pool shares then dilute only the existing shareholders.
In the example Series A, the investors buy 20%, yet the founders' stake falls from 62.3% to 47.1%, a 24.4% cut. The extra comes from topping the pool up to 12%, which adds new shares worth 4.4% of the company. Size the pool from your hiring plan for the next 18 to 24 months rather than accepting a round number.
How SAFEs dilute you
A post-money SAFE gives its investor investment ÷ valuation cap of the company, measured just before the next priced round. The example's $750K SAFE on a $7.5M cap is 10%, and the founders absorb all of it: their stake goes from 90% to 81%. Stack several SAFEs and every one comes out of the founders' share.
The SAFEs convert at the next priced round, and from then on SAFE holders are diluted like everyone else. If that round is priced below a SAFE's cap, the SAFE converts at the round price and gets more shares, which the calculator handles. For the exact share counts, use the SAFE calculator.
How much dilution is normal per round?
Selling about 20% per round has been the norm for years, and later rounds dilute less. Carta data on 12,435 US software rounds shows it drifting slightly lower:
| Round | 2021 | 2025 |
|---|---|---|
| Seed | 20% | 19% |
| Series A | 20% | 18% |
| Series B | 16% | 15% |
| Series C | 12.5% | 9.6% |
Source: SaaStr's analysis of Carta data, January 2021 to May 2025.
How to limit dilution
- Raise for your next milestone, plus a buffer, not the most you can get. Every extra dollar is paid for in equity.
- Size the option pool from your hiring plan. Pool shares you don't need still come out of your stake in the pre-money.
- Track your SAFE stack. Each post-money SAFE dilutes only the founders until the priced round.
- Talk to more investors. Competition is what moves valuation. Angel Roster lists 70,000+ angels and VCs you can filter by stage and industry, starting with pre-seed and seed investors.
How the calculator works
- Ownership is fully diluted: it counts the whole option pool, granted or not. The model starts from a notional 10,000,000 shares; only the ratios matter.
- SAFE rounds are post-money SAFEs. Until a priced round, they're shown at investment ÷ cap; at the priced round they convert using Y Combinator's definitions, at the cap price or the round price, whichever is lower.
- Priced rounds top the option pool up to its target, as a share of the company after the round, inside the pre-money. No options are assumed to be granted between rounds.
- Stake values use each round's post-money valuation (or the SAFE cap). They're paper values, not what your shares would fetch in a sale.
- Not modeled: liquidation preferences, secondary sales, pro rata rights, and down rounds' anti-dilution.