SAFE Notes · 9 min read
SAFE Note Calculator: How SAFEs Convert to Equity
A SAFE (Simple Agreement for Future Equity) is the most common early-stage funding instrument in the US startup ecosystem. Created by Y Combinator in 2013, it lets startups raise money quickly without setting a valuation — the investor gets equity when the company raises a priced round. Understanding how SAFEs convert is essential for founders negotiating terms and modeling the impact on their cap table.
How does a SAFE work?
An investor signs a SAFE and wires money to the company. In return, they receive the right to convert that investment into preferred shares at the next priced round. The SAFE is not debt — there is no interest accruing and no maturity date (unlike a convertible note). The key terms that govern conversion are:
- Valuation cap — the maximum valuation at which the SAFE converts; protects early investors if the company raises at a high valuation
- Discount rate — a percentage discount off the priced round price (e.g., 20% discount means the SAFE converts at 80% of the round price)
- Most-Favored-Nation (MFN) clause — the SAFE automatically adopts better terms given to subsequent SAFEs, if included
A SAFE can include a cap only, a discount only, both, or neither (uncapped/undiscounted — rare and unfavorable to investors).
Pre-money SAFE vs post-money SAFE
YC released an updated SAFE format in 2018 — the post-money SAFE — which is now the standard. Understanding the difference is critical:
| Feature | Pre-money SAFE (original) | Post-money SAFE (2018+) |
|---|---|---|
| Cap applies to | Pre-money valuation at conversion | Post-money valuation (after SAFE converts) |
| Dilution from new round | Absorbed by SAFE holder too | SAFE holder's % is protected until new round |
| Predictability for investor | Lower — exact % depends on round size | Higher — investor knows their % at conversion |
| Founder impact | More complex to model | Founders absorb more dilution from SAFE stack |
With a post-money SAFE, the investor's ownership percentage is fixed at conversion based on the cap: ownership % = SAFE amount ÷ valuation cap. A $500K SAFE on a $5M cap gives the investor exactly 10% of the company at conversion, regardless of how large the next round is.
How to calculate SAFE conversion shares
The number of shares a SAFE converts to depends on the conversion price, which is the most favorable of the cap price or discount price:
Discount conversion price = Round price per share × (1 − discount rate)
Effective conversion price = min(cap price, discount price)
Shares issued to SAFE holder = SAFE investment ÷ effective conversion price
Worked example
A startup raised a $300K SAFE at a $4M cap and 20% discount. It later raises a Series Seed at a $6M pre-money valuation with 10,000,000 pre-money shares:
Cap price = $4,000,000 ÷ 10,000,000 = $0.40 per share
Discount price = $0.60 × (1 − 0.20) = $0.48 per share
Effective price = min($0.40, $0.48) = $0.40 per share (cap wins)
SAFE shares = $300,000 ÷ $0.40 = 750,000 shares
The SAFE investor receives 750,000 shares at $0.40 each, which at the round price of $0.60 represents a 33% discount — roughly equivalent to investing at a 50% markup to the round.
How SAFEs affect founder dilution
If a company raises multiple SAFEs before a priced round (a "SAFE stack"), the dilution at conversion can be surprising. Each SAFE converts separately, and the combined dilution from all SAFEs is only visible once a priced round closes.
A common mistake: founders mentally treat SAFEs as small bets with limited dilution because there's no share issuance at signing. But a $2M SAFE stack converting into a $5M Seed round can result in SAFE holders owning 25–40% of the company — before new investors enter.
SAFE vs convertible note
| Feature | SAFE | Convertible Note |
|---|---|---|
| Legal structure | Equity instrument | Debt (promissory note) |
| Interest | None | Yes (typically 4–8% per year) |
| Maturity date | None | Yes (typically 12–24 months) |
| Repayment risk | No — not debt | Yes — can be demanded at maturity |
| Complexity | Simple (5-page document) | More complex (legal terms required) |
| Common in | Pre-seed, seed stage US startups | Bridge rounds, international deals |
Model your SAFE conversion in Quozify
Add SAFEs with any cap and discount rate and see conversion shares calculated live.
SAFE notes — common questions
- What is a SAFE note and how does it work?
- A SAFE (Simple Agreement for Future Equity) is an investment contract where an investor provides capital today in exchange for the right to receive equity at a future priced funding round. Unlike a convertible note, a SAFE is not debt — it has no interest rate and no maturity date. The SAFE converts to preferred shares at the next priced round based on the terms: a valuation cap, a discount rate, or both.
- What is the difference between a pre-money SAFE and a post-money SAFE?
- A pre-money SAFE (the original YC format) converts at the next round's price or the cap price, whichever is lower, but the dilution to existing shareholders occurs before the new round's investors enter. A post-money SAFE (YC's updated 2018 format) guarantees the SAFE holder a specific ownership percentage after conversion, making dilution more predictable for the investor. The key difference is when the SAFE holder's dilution from the new round is calculated — before or after new investors enter.
- How do you calculate how many shares a SAFE converts to?
- SAFE shares = SAFE investment amount ÷ conversion price per share. The conversion price is the lower of: (1) the cap price = valuation cap ÷ pre-money fully diluted shares, or (2) the discount price = new round's price per share × (1 - discount rate). For example, a $500,000 SAFE with a $5M cap converting in a round priced at $8M pre-money on 10M shares: cap price = $5M ÷ 10M = $0.50/share; round price = $0.80/share. The SAFE converts at $0.50, giving 1,000,000 shares.
- Does a SAFE appear on the cap table before it converts?
- Yes, SAFEs appear on the cap table as unconverted instruments before the priced round. They are tracked as a dollar amount and their terms (cap, discount). For fully diluted ownership calculations, some cap tables include SAFEs on an as-converted basis using the current best estimate of the conversion price. Quozify shows SAFE and convertible note holders as separate stakeholder types until conversion.
- What is a valuation cap on a SAFE?
- A valuation cap sets the maximum valuation at which the SAFE will convert to equity. If the next priced round is valued above the cap, the SAFE investor converts at the cap price (benefiting from the lower conversion price) rather than the round price. This protects early investors who took risk at an earlier, higher-uncertainty stage from being diluted at the same price as later, lower-risk investors.