The difference between a pre-money and a post-money SAFE is which shares the valuation cap is measured against. A pre-money SAFE leaves all SAFEs out of that count, so SAFE investors dilute each other. A post-money SAFE counts all SAFE money, so each investor's stake is fixed at investment divided by cap, and later SAFEs dilute the founders instead.
Definition: A pre-money SAFE converts at a price based on the company's capitalization excluding all SAFEs (but including any option pool increase made in the priced round), while a post-money SAFE converts at a price based on capitalization including all SAFEs and notes (but excluding that pool increase).
Same cap, same check, different ownership. It's easy to miss.
Illustrative example: an investor puts $500K into a company on a post-money SAFE with a $5M cap. Y Combinator's user guide gives the answer directly: $500K divided by $5M is 10 percent, measured after all SAFE money and before the priced round. On a pre-money SAFE with the same cap, the same check would be about 9.1 percent going into the round if it were the only SAFE, and about 7.7 percent if the company also sold another $1M of SAFEs on the same cap.
How pre-money and post-money SAFEs calculate conversion
Both instruments convert into preferred stock when the company closes a priced round. The mechanics differ in one place: the share count used to turn the cap into a price.
Pre-money SAFE. Y Combinator introduced the original SAFE in late 2013 on a pre-money basis. Its conversion price is the cap divided by the company's capitalization before the SAFEs, and YC's user guide notes that this count included the option pool increase made for the Series A. Because the SAFEs are left out, each SAFE's share count is set without regard to the others, and the SAFEs then dilute each other when they all convert at once.
Post-money SAFE. Released in 2018, it divides the cap by a "company capitalization" that YC defines to include all outstanding shares, granted and promised options, the existing unissued pool, and all SAFEs and notes converting in the round, but to exclude any pool increase made in the priced round. The holder's percentage going into the round is simply investment divided by cap.
Pre-money vs. post-money SAFE: a side-by-side example
Take an illustrative company with 8,000,000 founder shares and no existing option pool. Two investors each put $500K on SAFEs with $10M caps, and the company then raises a $3M Series A at a $15M pre-money valuation. We ran the conversion both ways, with and without a 2,000,000-share option pool created in the round and counted in the pre-money.
| Scenario | Holder | Pre-money SAFE | Post-money SAFE |
|---|---|---|---|
| No new pool | Each SAFE investor | 3.8% | 4.2% |
| No new pool | Founders | 75.8% | 75.0% |
| 2M-share new pool | Each SAFE investor | 3.8% | 3.4% |
| 2M-share new pool | Founders | 60.6% | 61.2% |
The Series A investor ends at 16.7 percent in every case. Without a new pool, the post-money investor converts at $1.125 a share into 444,444 shares, versus 400,000 shares at $1.25 on the pre-money form. With the pool, the pre-money SAFE's price drops to $1.00 (500,000 shares) because the pool sits inside its conversion math. The post-money SAFE's price stays at $1.125, and its holder absorbs part of the pool.
The stacking effect grows with the stack. Three $1M SAFEs on $10M caps equal 30 percent of the company on post-money terms, but about 23.1 percent on pre-money terms, which is the kind of gap SeedLegals warns founders about. Founders can see the full cap table walk-through in how stacked SAFEs convert.
Who bears the dilution under each SAFE form
| Event | Pre-money SAFE holder | Post-money SAFE holder |
|---|---|---|
| More SAFEs sold before the priced round | Diluted | Not diluted |
| Option pool increase in the priced round | Not diluted | Diluted |
| New money in the priced round | Diluted | Diluted |
| Ownership known at signing | No | Yes |
YC's user guide says it plainly: under the post-money form the SAFEs are not diluted by each other, but they are diluted by the new or increased option pool adopted as part of the Series A. YC's reasoning is that otherwise founders would bear all of the dilution for two rounds of hiring while the SAFEs funded only one.
Why the post-money SAFE became the default
YC's documents page calls the biggest advantage of the post-money SAFE the fact that the ownership sold is immediately transparent and calculable for both founder and investor. Its user guide adds that founders can close with each investor as soon as both are ready, rather than coordinating a single closing, and that the switch reflected SAFE rounds growing into full seed rounds of their own. Today YC's documents page offers only post-money forms: three US versions (cap only, discount only, and uncapped MFN) plus a pro rata side letter. A cap-and-discount version was part of the 2018 release and was removed in 2021.
The market appears to have followed. Carta reports that 87 percent of SAFEs on its platform were post-money in the third quarter of 2024, and its 2025 pre-seed review calls the post-money SAFE with a cap and no discount the standard instrument, with median caps near $10M for rounds of $250K to $1M and near $15M for rounds of $1M to $2.5M.
"But the post-money SAFE just protects the investor"
For the investor, it mostly does. Your percentage is set at signing, and nobody who signs after you can shrink it before the priced round.
But that protection is paid for by the founders, who absorb every later SAFE. Stack enough of them and the team walks into the Series A already thin, and a thin founding team is a problem for everyone on the cap table, you included. It's one of the red flags in our take on reading the cap table. The post-money form is a better instrument for you. Just watch what the stack is doing to the people who have to build the company.
What to check before signing either SAFE form
- Which form is it? YC's current forms are post-money SAFEs built around a defined "Post-Money Valuation Cap." Older pre-money forms still circulate, and some founders modify terms.
- What's in "company capitalization"? On a post-money SAFE, confirm it includes all outstanding SAFEs and notes and excludes the new pool. Modified definitions change the price.
- How much is already committed? Add each outstanding post-money SAFE as investment divided by cap. A large total leaves less room for the priced-round lead; the right ceiling varies by company.
- Pro rata rights. SAFE holders are not stockholders. Cooley GO notes the pre-money SAFE contemplated a pro rata rights agreement covering securities sold after the equity financing, while the post-money SAFE relies on YC's optional side letter covering the round in which the SAFE converts.
- Mixed instruments. Pre-money SAFEs, post-money SAFEs and convertible notes in the same company convert on different bases. We'd build the pro forma before wiring; the note side is covered in SAFE vs. convertible note.
Where the two SAFE forms trip up investors
- Treating the cap as a valuation. Neither SAFE prices the company. The cap is a conversion ceiling, and the post-money valuation of the priced round can be far above or below it.
- Forgetting the pool on a post-money SAFE. A large pool increase negotiated by the Series A lead lands on post-money SAFE holders as well as founders.
- Assuming a post-money SAFE protects against everything. It protects against later SAFEs, not the pool increase, the priced round, down rounds or later preferences.
- Interview traps. Fund interviewers like to ask candidates to convert two SAFEs of different types in one round; the venture capital cap table interview guide includes that exercise.
Founders deciding whether to use SAFEs at all may want to start with SAFE vs. priced round.
Learning SAFE mechanics on real deals
The difference between the two forms usually lands the day a conversion spreadsheet refuses to match the founder's number. Doing that on a company that's actually raising is the point of 1752vc's Venture Fellow program, eight weeks of live virtual sessions in which Fellows read real pitch materials and run diligence on live companies, so the cap table in front of them has consequences attached. For the full investor checklist, read investing in a SAFE.
The bottom line
Before you model anything, find out which form you're holding. The cap tells you the ceiling. The form tells you whose shares count underneath it.
A pre-money SAFE shares the dilution with other SAFEs.
A post-money SAFE hands it to the founders and the pool.
Key takeaways
- A pre-money SAFE leaves SAFEs out of the conversion math, so SAFE investors dilute each other and their final stake is unknown until the priced round.
- A post-money SAFE fixes the investor's ownership at investment divided by cap, shifting dilution from later SAFEs onto founders.
- The post-money SAFE excludes the priced round's option pool increase, so its holders share that dilution, while pre-money SAFE holders largely avoided it.
- YC introduced the pre-money SAFE in 2013 and the post-money SAFE in 2018; by Q3 2024, 87 percent of SAFEs on Carta were post-money.
- Neither form is a valuation: the cap is a conversion ceiling, and in our view the pro forma is what matters.
Frequently asked questions
A pre-money SAFE sets its conversion price using the company's capitalization excluding all SAFEs, so SAFE investors dilute one another. A post-money SAFE includes all SAFEs and notes in that capitalization, so each investor's ownership is fixed at investment divided by valuation cap, and later SAFEs dilute the founders instead.
In our view, usually the post-money SAFE, because it fixes the investor's percentage at signing and protects it from SAFEs sold later. The trade-off is that post-money SAFE holders share in the dilution from an option pool increase made in the priced round, which the pre-money form largely shielded them from.
Usually, when several SAFEs are stacked: three $1M SAFEs on $10M caps take 30 percent on post-money terms versus about 23 percent on pre-money terms. The gap narrows, and can even reverse, when the priced round adds a large option pool, because post-money SAFE holders absorb part of that pool.
YC says SAFE rounds had grown into full seed rounds, and the post-money form makes the ownership sold immediately transparent and calculable for founders and investors. It also lets founders close with each investor as soon as both sides are ready, without coordinating a single closing.
Yes, but they appear to be a shrinking minority. YC's documents page now offers only post-money SAFE forms, and Carta reports that 87 percent of SAFEs on its platform were post-money in the third quarter of 2024. Pre-money SAFEs still appear on some cap tables, so it is worth checking which form you hold before modeling a conversion.
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.
