Key Takeaways
- A SAFE (Simple Agreement for Future Equity) gives investors the right to receive equity at a future priced round -- no debt, no interest, no maturity date
- Post-money SAFEs are the market standard (~90% of pre-seed rounds), fixing each investor's ownership percentage at signing
- The trade-off: post-money SAFEs give investors certainty, but each additional SAFE dilutes only the founders
- Stacking multiple post-money SAFEs is one of the most common sources of unexpected dilution at Series A
- The median valuation cap for pre-seed SAFEs is around $10M for a $1M raise (2025 Carta data)
What Is a SAFE?
A SAFE -- Simple Agreement for Future Equity -- is a fundraising instrument created by Y Combinator in late 2013. It gives an investor the contractual right to receive equity in a future priced round (like a Series A), without creating debt. There is no interest rate, no maturity date, and no repayment obligation. You take the money now, and the investor gets shares later when the company raises a priced round.
The original motivation was simplicity. Before SAFEs, early-stage fundraising typically used convertible notes, which are structured as debt and carry interest, maturity dates, and more complex legal terms. Y Combinator designed the SAFE to strip all of that away, making it faster and cheaper for founders to close early rounds -- sometimes in a matter of days rather than weeks.
That simplicity worked. SAFEs have become the dominant instrument for pre-seed and seed funding. In Q1 2025, SAFEs comprised a record high of 90% of all pre-seed rounds on Carta, with convertible notes making up the remaining 10%.
How a SAFE Works: The Basic Flow
The lifecycle of a SAFE follows four steps:
1. Signing. The founder and investor agree on a valuation cap (and optionally a discount). The investor wires money. The SAFE is signed -- typically a 5-page document. No shares are issued yet.
2. Waiting. The SAFE sits on your cap table as a convertible instrument. The investor has no shares, no voting rights, and no board seat (unless negotiated separately via side letter).
3. Trigger event. When the company raises a priced equity round (the "Equity Financing"), the SAFE automatically converts into preferred shares. This is mandatory -- neither party has a choice.
4. Conversion. The SAFE investor receives shares of the same class being issued in the priced round (e.g., Series A Preferred), but at a lower price per share (determined by the valuation cap or discount), rewarding them for investing earlier.
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Key Terms on a SAFE
| Term | What It Means | Market Standard (2025) |
|---|---|---|
| Valuation Cap | The maximum valuation at which the SAFE converts. If the priced round values the company higher, the SAFE investor converts at the cap, getting more shares per dollar invested. | ~$10M cap for ~$1M raised at pre-seed |
| Discount | A percentage discount to the priced round price. If the Series A price is $2.00/share and the discount is 20%, the SAFE investor pays $1.60/share. | 20% when included (63% of SAFEs with discounts use 20%) |
| Cap Type | Pre-money or post-money. Determines whether the SAFE investment is included in the valuation cap denominator. | Post-money (standard since YC's 2018 update) |
| MFN (Most Favoured Nation) | If a subsequent SAFE has better terms (lower cap, higher discount), this SAFE automatically gets those terms. | Common in side letters, especially from institutional investors |
| Pro-Rata Rights | Right to invest proportionally in future rounds to maintain ownership percentage. | Often in side letters; not in the standard SAFE form |
| Conversion Trigger | The event that causes the SAFE to convert -- typically a priced equity round of any size. | No minimum threshold in post-money SAFE |
Cap vs Discount -- Which Applies?
If a SAFE has both a valuation cap and a discount, the investor gets whichever produces a lower price per share (i.e., more shares). In practice, the cap almost always produces the better deal for early investors, which is why 61% of SAFEs in 2025 use a valuation cap only, with no discount.
Pre-Money vs Post-Money SAFEs: The Critical Difference
This is the distinction that changed early-stage fundraising. The original 2013 YC SAFE was a pre-money SAFE. In 2018, YC introduced the post-money version, which quickly became the market standard.
| Pre-Money SAFE (2013 Version) | Post-Money SAFE (2018 Standard) | |
|---|---|---|
| Investor ownership at signing | Unknown -- depends on total SAFEs issued and conversion mechanics | Fixed. Ownership % = Investment / Valuation Cap |
| Who bears dilution from additional SAFEs? | All SAFE holders dilute each other (and the founders) | Only the founders. Each new SAFE investor's % is locked in |
| Cap table clarity | Low -- cannot model the cap table accurately until conversion | High -- ownership is calculable immediately |
| Founder dilution | Lower per SAFE (dilution is shared) | Higher per SAFE (founders absorb all dilution from subsequent SAFEs) |
| Market share (2025) | ~10% | ~90% |
Why Post-Money Became the Standard
The post-money SAFE won because it solved a real problem for investors: uncertainty. With pre-money SAFEs, an investor putting in $500K at a $5M cap could not know their final ownership until all SAFEs were closed and converted. If the founder raised another $500K SAFE afterward, the first investor's ownership would be diluted -- even though their cap was the same.
Y Combinator itself called this a "huge advantage" for both parties, noting it allows everyone to calculate ownership precisely at the time of signing. From the founder's perspective, the trade-off is clear: post-money SAFEs are easier to understand and faster to close, but they shift all incremental dilution from additional SAFEs onto the founders.
Post-Money SAFE Conversion: Step by Step
Let's walk through exactly how a post-money SAFE converts when a priced round happens.
Setup
Company: FounderCo -- 10,000,000 shares outstanding (all common, held by founders)
SAFE: $1,000,000 invested on a $10,000,000 post-money valuation cap
Series A: $5,000,000 raised at $15,000,000 pre-money valuation
Step 1: Calculate the SAFE investor's ownership percentage.
SAFE Ownership % = Investment / Post-Money Cap = $1M / $10M = 10%
This 10% is locked in at signing. It does not change regardless of how much the company raises in additional SAFEs.
Step 2: Determine "Company Capitalisation" for conversion.
Under the post-money SAFE, "Company Capitalisation" means all shares outstanding immediately before the SAFE converts -- founders' shares plus any option pool or promised options. In this case, that's 10,000,000 shares.
Step 3: Calculate the conversion price.
Conversion Price = Post-Money Cap / Company Capitalisation = $10M / 10M shares = $1.00/share
Step 4: Calculate shares issued to SAFE holder.
SAFE Shares = Investment / Conversion Price = $1M / $1.00 = 1,000,000 shares
But wait -- if you check the ownership: 1,000,000 / (10,000,000 + 1,000,000) = 9.09%, not 10%. The YC formula actually accounts for this by using a slightly different calculation that ensures the investor gets exactly 10% post-conversion:
SAFE Shares = (Ownership% / (1 - Ownership%)) x Company Cap = (0.10 / 0.90) x 10M = 1,111,111 shares
Now: 1,111,111 / 11,111,111 = exactly 10.0%. This is the correct formula from the YC post-money SAFE documentation.
Step 5: Series A shares are issued.
The Series A investor then purchases shares at the Series A price ($15M pre-money / 11,111,111 shares = $1.35/share). Their $5M buys 3,703,704 shares. The post-Series A cap table:
| Shareholder | Shares | Ownership % |
|---|---|---|
| Founders | 10,000,000 | 67.5% |
| SAFE Investor | 1,111,111 | 7.5% |
| Series A Investor | 3,703,704 | 25.0% |
| Total | 14,814,815 | 100% |
Note that the SAFE investor's ownership went from 10% (pre-Series A) to 7.5% (post-Series A). They were diluted by the Series A, just like the founders. The 10% was their ownership before the priced round, not after.
Key Insight
The SAFE investor's valuation cap ($10M) was well below the Series A pre-money ($15M). This means they got a better price per share than the Series A investor -- $0.90 vs $1.35. That price difference is the reward for investing earlier and taking more risk.
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Model single and stacked SAFEs, compare pre-money vs post-money dilution, and see your cap table after conversion. Try the Calculator →
Stacking Multiple SAFEs: Where Dilution Compounds
This is where post-money SAFEs can create problems for founders who are not tracking carefully. Because each SAFE investor's ownership is fixed independently, multiple SAFEs at the same cap produce additive dilution -- and it all comes from the founders' share.
Stacking Example: Three SAFEs at the Same Cap
SAFE 1: $500K at $5M post-money cap -- 10% ownership locked
SAFE 2: $500K at $5M post-money cap -- 10% ownership locked
SAFE 3: $250K at $5M post-money cap -- 5% ownership locked
Total committed: 25% to SAFE holders before the priced round even starts.
If the founders then raise a Series A that takes 20%, they are down to 55% -- and that is before any option pool expansion. Add a 10% pool refresh and the founding team is at ~49.5% by Series A.
Compare this to pre-money SAFEs, where the same three investors would have diluted each other, resulting in less total founder dilution. The difference is typically 1-3 percentage points for $1-2M raised -- meaningful equity that compounds across future rounds.
The Stacking Problem
With post-money SAFEs, model your fully converted cap table after each SAFE you sign -- not just at the end of the round. It is easy to lose track when you are signing SAFEs over several months. Three SAFEs at $500K each on a $5M cap = 30% committed before Series A. Founders are sometimes surprised by this at conversion.
SAFE vs Convertible Note: Which to Use
| SAFE | Convertible Note | |
|---|---|---|
| Legal structure | Equity instrument (contractual right to future shares) | Debt instrument (loan that converts to equity) |
| Interest | None | Yes -- median 7% annually (2025 data) |
| Maturity date | None | Yes -- typically 18-36 months. If not converted by maturity, the note is technically repayable |
| Legal cost | ~$0-$2K (standard form, minimal negotiation) | ~$5K-$15K (more customisation, debt documentation) |
| Speed to close | Days (standardised YC form) | 1-3 weeks (more negotiation) |
| Market share (pre-seed, 2025) | ~90% | ~10% |
| Best for | Pre-seed and seed rounds, angel investors, speed | Bridge rounds, biotech/pharma, institutional investors who prefer debt structure |
For most pre-seed and seed founders, SAFEs are the clearer choice. They are faster, cheaper, and standard enough that most investors will not push back on the form. SAFEs dominate pre-seed and early seed rounds, with 90% of pre-seed deals in Q1 2025 using SAFEs.
Convertible notes still make sense in specific situations: bridge rounds between priced financings, industries like biotech where investors prefer debt treatment, or when an investor requires interest and maturity protections. SAFEs have largely replaced convertible notes, used in 92% of pre-seed rounds as of Q3 2025, though industries with the highest representation of convertible notes include energy, biotech/pharma, and medical devices.
Types of SAFEs: Which One Are You Signing?
| SAFE Type | How It Works | Market Usage |
|---|---|---|
| Post-money, cap only | Converts at the valuation cap. No discount. Investor ownership = Investment / Cap. | ~61% of all SAFEs (most common) |
| Post-money, cap + discount | Investor gets the better of the cap price or discounted Series A price. | ~20% of SAFEs |
| Post-money, discount only | No cap -- converts at a discount to the next round price. Less common because investors lack upside protection. | Rare (~5%) |
| Post-money, MFN (no cap, no discount) | Terms automatically adjust to match the best terms given to any subsequent SAFE investor. | Used for very early cheques before terms are set |
| Pre-money SAFE | Original 2013 version. Cap does not include the SAFE amount. All SAFE holders dilute each other. | ~10% -- declining |
Don't Mix Types
Signing some pre-money and some post-money SAFEs in the same round creates conversion complexity that can be difficult to untangle at Series A. Decide on one type before you start the round and use it consistently. Your lawyer will thank you.
2025-2026 SAFE Market Data
Here are the current benchmarks from Carta's State of Pre-Seed and State of Seed reports:
| Metric | Data Point | Source |
|---|---|---|
| SAFE share of pre-seed rounds | 90% (Q1 2025), 92% (Q3 2025) | Carta State of Pre-Seed |
| Most common SAFE type | Post-money with cap only (61%) | Carta State of Seed 2025 |
| Standard discount (when included) | 20% (used in 63% of discounted SAFEs) | FutureSight / Carta |
| Median val cap: rounds under $250K | $7.5M | Carta Q2 2025 |
| Median val cap: rounds $250K-$500K | $10M | Carta Q2 2025 |
| Median seed valuation | $20M post-money | Carta State of Seed 2025 |
| Median dilution: $1M-$1.9M raised on SAFEs | 15.6% | FutureSight / Carta |
| AI companies' share of seed capital | 42% (2025) | Carta State of Seed 2025 |
| Convertible note median interest rate | 7% | Carta Q1 2025 |
Regional Caveat
These figures are primarily from US data via Carta. UK valuations typically run 20-40% lower for equivalent-stage companies. MENA markets have less standardised data, but generally follow UK pricing with additional variance. If you are raising in London or Dubai, adjust your expectations accordingly.
What Founders Should Watch For
1. Track cumulative SAFE dilution in real time. After signing each SAFE, update your fully converted cap table. Do not wait until Series A to discover you have committed 30% to SAFE holders. A simple spreadsheet tracking each SAFE's implied ownership is sufficient.
2. Understand "Company Capitalisation." This is the denominator used to calculate conversion price. In a post-money SAFE, it includes all shares outstanding before conversion -- founders, option pool, and promised options. It does not include shares from other SAFEs converting simultaneously. Read the definition in your SAFE carefully; different versions have subtle differences.
3. Watch for side letter terms. The standard SAFE form is relatively founder-friendly. But institutional investors often attach side letters with pro-rata rights, information rights, and MFN clauses. These are not necessarily bad, but you should understand what you are agreeing to -- especially MFN, which can retroactively change prior SAFE terms.
4. Do not over-optimise the valuation cap. A very high cap reduces dilution from the SAFE but creates a problem: if your Series A valuation does not reach the cap, the SAFE converts at the Series A price instead. In that scenario, you gave the SAFE investor no discount for investing early, which can create friction. Set caps that reflect a reasonable step-up from your current stage.
5. Get a startup lawyer for your first SAFE. The standard YC form is free and well-documented. But understanding how it interacts with your specific cap table, option pool, and state of incorporation is worth the $1-3K legal cost. Subsequent SAFEs on the same terms will not need additional legal review.
6. Know what triggers conversion. Under the post-money SAFE, any priced equity round triggers conversion -- there is no minimum raise threshold. This means even a small priced round will convert all outstanding SAFEs, which can have unintended cap table consequences if you were not planning for it.
The YC SAFE Templates
The official SAFE templates are available free at ycombinator.com/documents, along with a detailed user guide. These are the standard forms -- if an investor presents a modified version, compare it line by line against the official template to spot changes.
Frequently Asked Questions
What is a SAFE agreement?
A SAFE (Simple Agreement for Future Equity) is a fundraising instrument that gives investors the right to receive equity at a future priced round. It is not debt -- there is no interest, no maturity date, and no repayment obligation. Created by Y Combinator in 2013, SAFEs are now used in about 90% of pre-seed rounds.
What is the difference between pre-money and post-money SAFEs?
A pre-money SAFE does not include the SAFE investment in the valuation cap, so investor ownership is not known until conversion. A post-money SAFE includes it, which fixes each investor's ownership percentage at signing. Post-money is the current standard (~90% market share).
How does a post-money SAFE convert?
When the company raises a priced round, the SAFE automatically converts into preferred shares. The conversion price = valuation cap / company capitalisation. The investor receives shares at this price, which is lower than the Series A price, rewarding them for investing earlier.
What is a valuation cap?
A valuation cap is the maximum valuation at which a SAFE converts. If the priced round values the company higher, the SAFE converts at the cap (more shares per dollar). The median pre-seed cap is around $7.5-$10M depending on round size (2025 data).
Should I use a SAFE or convertible note?
For most pre-seed and seed rounds, SAFEs are the standard. They are faster, cheaper, and simpler. Convertible notes are better suited for bridge rounds, biotech/pharma, or situations where investors require debt structure with interest and maturity protections.
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Sources & References
- Y Combinator, "Safe Financing Documents". ycombinator.com
- Y Combinator, "Primer for Post-Money Safe v1.1". ycombinator.com
- Carta, "Pre-Money SAFEs vs. Post-Money SAFEs" (2025). carta.com
- Carta, "State of Pre-Seed: Q1 2025". carta.com
- Carta, "State of Pre-Seed: Q3 2025". carta.com
- FutureSight Ventures / Carta, "Top 15 Pre-Seed and Seed Benchmarks" (February 2026). futuresight.ventures
- SaaStr / Carta, "The Real State of Seed Today: Top 10 Learnings from 50,000 Startups" (December 2025). saastr.com
- Promise Legal, "Post-Money SAFE: Complete Guide" (January 2025). promise.legal
- Promise Legal, "SAFE vs Convertible Note: Complete Comparison" (October 2025). promise.legal
- CRV, "SAFE vs. Convertible Note: Complete Founder's Guide". crv.com
- Alexander Jarvis, "SAFE Calculator for the YC Post-Money SAFE" (April 2025). alexanderjarvis.com
- Chris Harvey / Law of VC, "YC's Secret SAFE". lawofvc.substack.com
Frequently Asked Questions
What is a SAFE agreement?
A SAFE (Simple Agreement for Future Equity) is a fundraising instrument created by Y Combinator in 2013. It gives investors the right to receive equity in a future priced round, without creating debt or requiring interest payments or a maturity date. SAFEs are the dominant instrument for pre-seed and seed rounds, used in roughly 90% of pre-seed deals.
What is the difference between a pre-money and post-money SAFE?
A pre-money SAFE bases conversion on the company's valuation before SAFE investment. All SAFE holders dilute each other, so investor ownership isn't known until conversion. A post-money SAFE includes the SAFE in the valuation cap, fixing each investor's ownership percentage at signing. Post-money SAFEs are the current market standard (90%+ of pre-seed rounds).
How does a post-money SAFE convert?
When the company raises a priced round (e.g., Series A), the SAFE automatically converts into preferred shares. The conversion price is calculated as the valuation cap divided by the company capitalisation (all shares outstanding before conversion). The investor receives shares equal to their investment divided by this conversion price.
What is a valuation cap on a SAFE?
A valuation cap is the maximum valuation at which a SAFE converts to equity. If the company's priced round values it higher than the cap, the SAFE investor converts at the cap price, getting more shares per dollar invested. The median valuation cap for pre-seed SAFEs is around $10M for a $1M raise, as of 2025 Carta data.
Should founders use SAFEs or convertible notes?
For most pre-seed and seed raises, SAFEs are the standard choice — simpler, no interest, no maturity date, faster to execute. Convertible notes are more common in biotech/pharma, medical devices, and later-stage bridge rounds where institutional investors prefer debt structure. About 90% of pre-seed rounds now use SAFEs.