SAFEs and Convertible Notes: What They Are and How They Convert

A SAFE (Simple Agreement for Future Equity) and a convertible note are both ways for a startup to raise money now and issue shares later, at a future priced financing round, rather than pricing the company's equity at the time of the investment. Both are standard early-stage fundraising instruments. They are not the same thing: a SAFE is not debt, and a convertible note is.

What a SAFE is

A SAFE is an agreement between a company and an investor: the investor puts in money today, and in exchange receives the right to shares later, typically when the company raises a priced equity round. A SAFE is not a loan. It carries no interest rate, no maturity date, and no repayment obligation. If the company never raises a future priced round (or is acquired or liquidated first), the SAFE converts or settles under the terms the agreement specifies for that outcome instead.

What a convertible note is

A convertible note is debt: a loan that accrues interest from the date it's issued and comes due on a stated maturity date. Instead of being repaid in cash, the note is designed to convert into equity at a future priced round, on the same general cap/discount mechanics as a SAFE, with the loan's principal plus any accrued interest.

Because a note is debt, it carries a legal maturity date and an outstanding balance (principal plus accrued interest) that compounds the risk if the company doesn't raise a next round in time: an investor can, in principle, demand repayment or force a renegotiation at maturity, a mechanic a SAFE simply doesn't have.

The core mechanics: valuation cap, discount, and MFN

Both instruments give the early investor downside protection and upside participation through the same handful of terms, set when the instrument is issued:

• Valuation cap. A ceiling on the company valuation used to price the investor's conversion, regardless of what the priced round's own valuation turns out to be. A lower cap is better for the investor: it means more shares for the same dollars if the company's value has grown.
• Discount. A percentage reduction off the price per share that new investors pay in the priced round. A 20% discount means the SAFE or note holder converts at 80% of the round's share price.
• Better-of, not both-at-once. When an instrument carries both a cap and a discount, it converts at whichever produces the lower price per share (more shares) for the holder: the capped price or the discounted price, not a further discount stacked on top of the capped price.
• MFN ("most favored nation") clause. A clause, generally used on SAFEs, under which an earlier investor's terms automatically upgrade to match the best terms of a later SAFE issued before the round, if that later SAFE is more favorable (a lower cap or a higher discount). It protects an early, uncapped, or lightly-termed investor from being undercut by a later investor who negotiated a better deal.
• A note's interest and maturity. A convertible note additionally accrues simple interest (typically non-compounding, calculated on an actual-days/365 basis) on its principal from issuance until it converts or is repaid, and carries a maturity date by which it must either convert or be repaid or extended. A SAFE has neither.

An uncapped SAFE or note (no valuation cap set) converts purely at its discount to the round price, or at the round price itself if it has no discount either, making it economically closest to simply investing in the round at the round's own price.

Post-money vs. pre-money SAFE

The cap applies against a different "size of the company" depending on which variant was used, and the difference matters:

• Pre-money SAFE. The valuation cap is measured against the company's capitalization before the new round, and before other SAFEs and notes convert alongside it. Each pre-money SAFE sizes independently off its own cap, so pre-money SAFEs don't dilute each other's conversion price.
• Post-money SAFE. The valuation cap is measured against the company's capitalization including all the SAFE shares converting in that same round. Because each SAFE's own converted shares are part of the denominator used to price every SAFE, pricing a batch of post-money SAFEs together requires solving the set simultaneously rather than one at a time: in practice this means the exact ownership percentage a post-money SAFE investor is promised (e.g., "this SAFE equals 5% of the company, fully diluted, post-money, before the new round's investors") is fixed up front, which is precisely the certainty a post-money SAFE is designed to give the investor that a pre-money SAFE doesn't.

A convertible note's cap works on the pre-money logic described above (the note's own conversion price is set against the pre-round share count, independent of other converting instruments), reflecting that the post-money SAFE structure is a SAFE-specific convention, not a convertible-note one.

How they convert at a priced round

When a company closes a priced equity round, every outstanding SAFE and note with no earlier settlement event converts into shares of the new round's preferred stock, by the following general sequence:

1. Any MFN clauses are resolved first. Every SAFE carrying an MFN clause adopts the most favorable cap and discount available among SAFEs issued after it, before any conversion math runs.
2. The round's own share price is set from the new investors' pre-money valuation divided by the company's pre-round fully diluted share count (which includes the full, unallocated option pool, not just shares already granted).
3. Each SAFE or note's conversion price is the better of its capped price or its discounted price (whichever is lower, per the better-of rule above), applied to that instrument's principal or purchase amount to produce its share count. A note also adds any interest accrued since issuance to the balance that converts.
4. Post-money SAFEs, and the round's new option pool increase, are solved together with the round's new preferred shares, because each depends on the company's resulting total share count, which in turn depends on them. This is an iterative calculation, not a single pass: a well-formed round converges to one stable share price and share count; a round specified with terms that can't all be satisfied (for example, SAFE claims plus a target option pool that together exceed the company) has no such stable point and should be rejected rather than returning a half-solved result.
5. Existing preferred stock with anti-dilution protection is adjusted if the new round prices below an earlier round (a "down round"), under whatever anti-dilution formula that earlier series' terms specify.

Dilution impact on the cap table

Every dollar that converts from a SAFE or note, plus the round's new investor shares and any increase to the option pool, adds new shares to the company's fully diluted share count. Because existing holders' ownership is a share of that same total, their percentage ownership goes down even though their share count doesn't change, the standard mechanism of dilution. The resulting post-round fully diluted count is, at a mechanical level: the pre-round share count, plus the shares the converting SAFEs and notes receive, plus the new round's preferred shares, plus the round's increase to the option pool.

A valuation cap, by fixing how many shares an early investor's dollars convert into regardless of how the company's value has grown, is itself a dilution lever: a lower cap means more shares go to that early investor and proportionally less of the pie is left for the founders and other existing holders once the round closes. This is also why a company's choice of cap, discount, and whether to use post-money or pre-money SAFEs has a real, calculable effect on founder dilution well before any term sheet for the next priced round is signed. Modeling a specific round's dilution impact before it closes, rather than finding out after, is most useful when it's run against the company's actual, current cap table rather than a rough spreadsheet copy; see how Value8 does SAFEs and convertible notes for how that modeling works end to end.

SAFE vs. convertible note vs. priced round

A priced round is the reference point both instruments are deferring to: it's the event that finally sets a per-share price, at which every outstanding SAFE and note converts. A company can, and commonly does, stack multiple SAFEs and notes with different terms across several smaller raises before its first priced round, which is exactly the scenario the MFN clause and the cap-table-wide round-conversion math above exist to handle correctly.

Dilution math at a priced round is closely related to, but distinct from, dilution math at an exit (an acquisition or IPO): see what a 409A valuation is for how a company's capitalization, including outstanding SAFEs and notes, feeds into the separate valuation used to price option grants.

This is general information about SAFE and convertible note market practice, not legal or financial advice. Confirm specific instrument terms with qualified legal counsel.