SAFE Dilution Calculator

See how much of your company you are giving up. This free SAFE dilution calculator models post-money SAFEs (the instrument used in roughly 90% of pre-seed rounds), then adds your next priced round and option pool, so you can see founder dilution the way investors calculate it. No signup, and we don’t capture any data from your entries.

How to use this calculator

1. Enter each SAFE you have signed. Use the amount raised and the post-money valuation cap from the agreement. If a SAFE has a discount instead of (or alongside) a cap, add it. Otherwise leave discount at 0.
2. Read the headline number. This is the percentage existing holders (you, your co-founders, and your team) still own after the SAFEs convert.
3. Model your next priced round. Toggle it on and enter the pre-money valuation, the new money you expect to raise, and the option pool your lead investor will likely require (10% is a common ask). The table shows ownership at SAFE conversion and after the round.
4. Share the scenario. “Copy shareable link” saves your inputs in the URL, so you can send a scenario to a co-founder or advisor.

The terms, in plain English

What is a SAFE?

A SAFE (Simple Agreement for Future Equity) is the standard early-stage fundraising instrument created by Y Combinator. An investor gives you money today. In exchange, they get the right to shares when you raise your next priced round. A SAFE has no interest and no maturity date, which is why SAFEs have largely replaced convertible notes at pre-seed and seed. On Carta, SAFEs were about 93% of pre-seed rounds in Q2 2026, and about 9 in 10 of those SAFEs were post-money (source: Carta, August 2026).

Post-money valuation cap

The valuation cap sets the maximum price at which the SAFE converts to shares. With a post-money SAFE (the current YC standard), the math is simple: ownership = investment ÷ post-money cap. Raise $500,000 on a $10 million post-money cap and that investor owns 5%. That percentage is locked in, no matter what else you raise on other SAFEs. The certainty helps investors, and it is why founders need to watch the other side of it: every post-money SAFE percentage comes out of the existing holders’ share.

Discount rate

Some SAFEs carry a discount (typically 10 to 25%) instead of a cap, or alongside one. At conversion the investor pays the discounted price of your priced round. If the SAFE has both terms, they get whichever is better for them. In practice the cap usually wins at seed stage, and the discount is the fallback for rounds priced below expectations.

Dilution

Dilution is the reduction in your ownership percentage as new shares are issued. SAFE dilution does not show up day to day, because nothing converts until a priced round. That is how founders end up surprised. Stack three or four SAFEs and you can commit 20 to 30% of the company before a single share is issued. For reference, Carta’s Q2 2026 benchmarks put median seed-round dilution at 19.4% (source: Carta, October 2026).

Option pool (and the “shuffle”)

Lead investors typically require an employee option pool, often 10% of the post-round company, created before their money comes in. That sequencing is the “option pool shuffle”: the pool dilutes existing holders and SAFE investors, not the new investor. It is one of the most negotiable and least understood terms in a term sheet, and it is why this calculator asks for the pool separately.

What happens when your SAFEs convert

In a typical early-stage sequence, you raise one or more SAFE rounds (pre-seed, angel checks, maybe a seed extension). Then a priced equity round, usually a seed or Series A led by a venture fund, triggers everything at once:

1. SAFEs lock their percentages. Each post-money SAFE converts at investment ÷ cap (or the discounted round price, if better). Existing holders absorb all of this dilution.
2. The option pool is topped up to the size the lead investor requires, diluting everyone who existed before the round.
3. New investors buy their stake, which equals new money ÷ post-money valuation of the round.

Worked example: you raised $1M on a $10M post-money cap (10%) and $500K on an $8M cap (6.3%). A Series Seed at $20M pre-money with $5M new money and a 10% pool leaves existing holders with 58.6%. Try it in the calculator above to see each holder’s line. For the mechanics of caps versus priced equity, read our guide to SAFE notes vs. priced rounds.

Frequently asked questions

How much do SAFEs dilute founders?

Investment ÷ post-money cap for each SAFE, added together. $1.5M raised across SAFEs at a $10M post-money cap costs existing holders 15%. Multiple SAFEs stack, which is why modeling them together matters more than any single agreement.

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

Under the original pre-money SAFE (2013 to 2018), each new SAFE diluted the earlier SAFE holders too, so nobody knew their percentage until conversion. The post-money SAFE fixes each investor’s percentage up front. That is simpler for everyone, but it shifts all of the dilution onto founders and employees. Nearly all SAFEs signed today are post-money, and this calculator models the post-money standard.

Is an uncapped SAFE better for founders?

An uncapped SAFE (usually discount-only, or an MFN clause) defers the pricing question to your next round, so its dilution depends entirely on that round’s valuation. Model it here by adding the discount and toggling the priced round on.

How accurate is this SAFE dilution calculator?

It models ownership at the percentage level using the YC post-money SAFE mechanics, including the option pool shuffle. A real conversion is computed in shares on your cap table and can differ (share-level rounding, discount conversion mechanics, pro-rata side letters, existing pool re-use). Use it to prepare for negotiation. It is not legal or financial advice, and your lawyer runs the definitive numbers.

If you are planning the round itself, estimate what you are worth with the startup valuation calculator, then read the Startup Fundraising guides on term sheets, equity and vesting, and pitch decks.