SAFE dilution happens when your SAFEs convert into shares, usually at your first priced round. With the standard post-money SAFE, each investor's ownership equals the purchase amount divided by the post-money valuation cap, so you can calculate dilution the day you sign. A common mistake, in our view, is doing that math one SAFE at a time instead of across the stack.
Definition: A SAFE (Simple Agreement for Future Equity) is a contract in which an investor pays cash now for the right to receive shares later, typically when the company raises a priced equity round.
Each SAFE feels small when you sign it. The stack is what shows up at the Series A.
Why founders use SAFEs, and where the dilution hides
Y Combinator introduced the SAFE in late 2013 as a simpler alternative to convertible notes and released the post-money version in 2018. Unlike a convertible note, a SAFE is not debt: it carries no interest rate and no maturity date, so there's no repayment clock running while you build.
That simplicity is a big part of why SAFEs dominate early rounds. Carta's State of Pre-Seed 2025 in Review found that US startups on its platform raised $10.4 billion across 50,316 SAFEs and convertible notes in 2025, and it calls the post-money SAFE with a valuation cap and no discount the standard pre-seed instrument.
Because nothing shows up as dilution until conversion, it's easy to underestimate. If you're still deciding whether to raise on SAFEs at all, start with SAFE vs. priced round.
The SAFE terms that drive dilution
- Valuation cap. The highest valuation at which the SAFE converts. If your priced round comes in above the cap, the SAFE investor converts at the cap price and gets more shares per dollar than new investors. Carta's 2025 review puts median caps at about $10 million for rounds of $250,000 to $1 million and about $15 million for rounds of $1 million to $2.5 million.
- Discount. A percentage off the price new investors pay in the priced round. Cooley GO says discounts are often between 10 and 25 percent, and DLA Piper describes a wider typical range of 5 to 30 percent.
- Most favored nation (MFN). If you later issue SAFEs on better terms, an MFN holder can amend its SAFE to match. YC's MFN form is an uncapped SAFE with no discount.
- Pro rata side letter. YC's optional side letter gives an investor the right to buy into the priced round in which the SAFE converts, which reduces how much of that round is left for new investors.
YC's documents page currently lists three US post-money SAFEs (cap with no discount, discount with no cap, and uncapped MFN) plus the pro rata side letter. The 2018 release also had a cap-and-discount version; YC's user guide says it removed that form in August 2021 because it had not seen situations where that form was the preferred choice. If you're offered a SAFE with both a cap and a discount, it's a custom or older form, and the investor converts at whichever calculation gives more shares.
How post-money SAFE dilution works
The post-money SAFE measures the investor's ownership after all SAFE money is counted but before the new money in the priced round. YC's user guide gives the formula: purchase amount divided by post-money valuation cap. A $500,000 SAFE on a $5 million post-money cap buys 10 percent.
Three consequences worth knowing as a founder:
- SAFE holders don't dilute each other. YC's guide says so directly, so each additional SAFE comes out of the founders' and other existing holders' share.
- The priced round dilutes everyone afterward. When the Series A closes, new money dilutes founders and converted SAFE holders together.
- A new option pool dilutes SAFE holders too. The post-money SAFE excludes any pool increase made in the priced round from its conversion math, so that increase is shared by founders and SAFE holders.
The older pre-money SAFE split the burden differently; the side-by-side math is in pre-money vs. post-money SAFE, and how investors judge the same terms is covered in investing in a SAFE.
Worked example: two stacked SAFEs and a Series A
As an illustrative example, assume a company with 8,000,000 founder shares and a 1,000,000-share option pool, so 9,000,000 shares before any SAFE converts.
Step 1: add up the SAFE stack.
- SAFE A: $500,000 on a $5 million post-money cap, which is 10 percent.
- SAFE B: $1,000,000 on a $10 million post-money cap, which is also 10 percent.
Together the SAFEs own 20 percent when they convert. The company capitalization that includes the SAFE shares is 9,000,000 divided by 0.80, or 11,250,000 shares. Each SAFE receives 1,125,000 shares, and the founders' stake drops from 88.9 percent to 71.1 percent before any priced money arrives.
Step 2: price the Series A. A lead investor puts in $4 million at a $16 million pre-money valuation ($20 million post-money), with no option pool increase to keep the math simple.
- Price per share: $16,000,000 divided by 11,250,000 shares, about $1.42.
- New Series A shares: 2,812,500.
- Total shares after the round: 14,062,500.
| Holder | Shares | Ownership after Series A |
|---|---|---|
| Founders | 8,000,000 | 56.9% |
| Option pool | 1,000,000 | 7.1% |
| SAFE A and SAFE B | 2,250,000 | 16.0% |
| Series A investor | 2,812,500 | 20.0% |
SAFE A converted at about $0.44 per share and SAFE B at about $0.89, both well below the $1.42 Series A price. That gap is roughly what the cap is worth to the investors.
Step 3: see the stacking effect. If the company had raised only SAFE A, founders would own 80 percent going into the Series A and 64 percent coming out. The second $1 million SAFE cost the founders about 7 points of ownership after the round. Stacked SAFEs are easy to sign and can be painful in aggregate.
Discount-only example: a $250,000 SAFE with a 20 percent discount, in a round priced at $2.00, converts at $1.60 per share. The investor receives 156,250 shares, compared with 125,000 shares for a new investor paying the same amount.
"It's just a SAFE. It isn't real dilution yet."
It's a common line, and technically right: no shares change hands at signing. Plenty of founders reasonably put off the math until a priced round forces it.
But with a post-money SAFE, the investor's percentage at the cap is set the day you sign, and a priced round below the cap only raises it. Conversion just makes it visible. By the time a Series A lead models your stack, your ownership was decided months earlier, one small check at a time. We'd rather founders see the number when they can still change it.
The option pool and other hidden SAFE dilution
Series A leads often ask for a bigger option pool and want it included in the pre-money valuation, which lowers the price per share for everyone already on the cap table. Rerun the example with the lead requiring a 10 percent post-money pool and you see the effect: the company adds about 464,000 pool shares, the price falls to about $1.37, founders end at 54.6 percent instead of 56.9 percent, and the two SAFEs end at 15.4 percent instead of 16.0 percent. The new investor still gets exactly 20 percent. It may help to read option pool strategy before you negotiate the size of that top-up.
Pro rata side letters add one more layer. The priced round has to make room for both new investors and existing holders with pro rata rights. That can push the round, and your dilution, higher than planned, so count those rights before you agree a round size. YC's user guide points out the same squeeze.
Mistakes founders often make with SAFE dilution
- Tracking SAFEs outside the cap table. Record each SAFE, its cap and its side letters in your cap table the day it's signed. Our guide to cap table management covers the setup.
- Setting the cap too low to close fast. A low cap can buy speed now and cost you later: it can over-dilute your own shares or the shares reserved for Series A investors (Carta flags the same risk).
- Raising more than the next milestone needs. Every extra SAFE dollar is ownership. We'd tie the raise to specific milestones rather than to whatever the market will give you.
- Granting MFN clauses without a plan. An MFN from your first check can reprice itself to the terms of a later SAFE, although YC's guide notes the MFN typically allows only one amendment.
- Only modeling the base case. Run the conversion at a Series A below the cap, at the cap, and well above it, with and without a pool increase, so you can see the range of outcomes.
Raising your first round with support
Deciding how much to raise on SAFEs, and at what cap, is easier with experienced advisers in your corner. 1752vc's Accelerate is a remote program for early-stage startups ready to grow that invests $100K at a valuation cap of up to $3.5M, trains founders in founder-led sales, and connects them with a network of 850+ investors.
The bottom line
Add up every SAFE as investment divided by cap, treat the total like a round you've already closed, and model the Series A with a pool top-up before you sign the next check.
A SAFE doesn't wait for conversion to dilute you.
It just waits to tell you.
Key takeaways
- A post-money SAFE's ownership equals the investment divided by the post-money valuation cap, so you can calculate SAFE dilution at signing.
- Post-money SAFE holders do not dilute each other, which means each additional SAFE reduces founder ownership directly.
- In the worked example, two SAFEs totaling $1.5 million took founders from 88.9 percent to 56.9 percent after a $4 million Series A.
- An option pool increase in the priced round dilutes founders and post-money SAFE holders, but not the new investor.
- Consider keeping every SAFE on your cap table and modeling conversion at several Series A valuations before you sign the next one.
Frequently asked questions
Yes. A SAFE converts into shares, usually at the next priced round, and those new shares reduce the founders' percentage ownership. How much depends on the valuation cap, any discount, and the total SAFE money raised. It is worth modeling the full stack before you sign another one.
Divide the investment amount by the post-money valuation cap, then add up that figure for every SAFE you have issued. A $1 million SAFE on a $10 million post-money cap equals 10 percent at conversion. The priced round, and any option pool increase made in it, then dilutes founders and SAFE holders further.
There is no fixed rule, and the right number varies with your situation, round size and cap. One approach is to add up every SAFE as investment divided by cap and treat the total like a priced round you have already closed. The bigger that stack, the less room is left for the priced-round lead, who will usually want a meaningful stake and often a larger option pool.
The investor converts at whichever calculation yields more shares, which means the lower of the cap price and the discounted round price. YC removed its cap-and-discount post-money SAFE in 2021, so a combined cap and discount today is a custom term worth reviewing with counsel.
Cooley GO says SAFE discounts are often between 10 and 25 percent, and DLA Piper cites a broader range of 5 to 30 percent depending on stage and risk. Many SAFEs carry no discount at all: Carta calls the post-money SAFE with a cap and no discount the standard pre-seed instrument.
Sources
Disclaimer: This guide is for general education only and is not legal, tax or investment advice. Laws, market data and program terms change, so it may not reflect the latest developments or fit your situation. Treat it as a starting point, not a source of truth, and talk to a qualified lawyer, accountant or financial adviser before you make decisions.
