Convertible Note vs SAFE vs Priced Round Decision Calculator

Convertible Note vs SAFE: Which Instrument Dilutes Founders More

The convertible note vs SAFE question gets framed as a legal choice, but for a founder it is a dilution choice. Both instruments defer pricing to the next priced round and both convert at the lower of a cap-implied price and a discount-implied price. The single mechanical difference that matters is interest. A convertible note accrues interest — typically 2% to 8% simple — and that accrued amount converts into equity right alongside the original principal.

Run the numbers on a $1.5M raise at a $8M cap. A SAFE converts $1.5M of principal. A 6% note that sits for 18 months before conversion accrues about $135,000, so it converts roughly $1.635M. On a 10M-share fully-diluted base that is close to a full extra percentage point of founder ownership handed to the investor. The note is not a worse instrument — it gives the investor a maturity date and a default right, which some angels genuinely want — but in a side-by-side dilution comparison the SAFE is the cheaper one for the founder.

Because the interest gap is small, the convertible note rarely wins this calculator on the math alone. It tends to surface when an anchor investor specifically values the maturity clock, which the engine captures as a higher Investor Friendliness score for the note (80, versus 60 for a SAFE).

Convertible Debt vs Equity: When Each Structure Is Right

Stepping up a level, the real fork is convertible debt vs equity. A convertible note is debt that converts; a SAFE is a forward contract on equity; a priced round is equity issued today. The trade is about when pricing risk lands and whether a clock is attached. A note defers the price but adds a maturity date — if no priced round happens before maturity, the founder faces forced conversion at the cap or repayment of cash the company probably does not have.

A SAFE removes the clock entirely: it can sit on the cap table indefinitely until a priced round, acquisition, or dissolution forces conversion. That is why the SAFE displaced the convertible note as the pre-seed default — for a founder, debt with a maturity clock is strictly worse than the same economics with no clock. Priced equity is the opposite end: it deletes the deferral by setting the price now, which is the right move only when the round is large enough and the valuation defensible enough that pricing today does not lock in a bad mark.

The decision engine encodes this as the Optionality dimension — a SAFE scores 90, a note 70, a priced round 50 — because each step from SAFE to note to priced round trades flexibility for finality.

Post Money SAFE: How the YC Default Actually Works

The post money SAFE is the version Y Combinator published in 2018, and it is now the instrument behind almost every pre-seed round in the United States. Its defining feature is in the name: the valuation cap is a post-money number, so an investor’s ownership is fixed the moment the SAFE is signed. A $500K SAFE at a $6M post-money cap locks in exactly 8.33% of the company — 500,000 divided by 6,000,000 — and that fraction does not move when later SAFEs convert.

That fixed-ownership property is the whole point. Under the older pre money SAFE, a founder stacking three or four SAFEs could not know their total dilution until every SAFE converted at once, because each SAFE’s ownership was measured before the others. The post money SAFE makes the arithmetic legible up front — you can add the percentages. Searches for the YC form, including the one-word query ycombinator safe, dwarf searches for any other seed instrument, which is a direct readout of how completely this document won the pre-seed market.

The trade the post-money structure makes is that the founder, not the investor, absorbs the dilution from every later SAFE and from the new option pool. That is fine when SAFEs are few. It becomes a problem once four or more stack up, which is the exact condition that drops a SAFE’s Future-Round Readiness score in this tool.

Pre Money SAFE: The Older Variant and Why It Still Matters

The pre money SAFE is the original 2013 Y Combinator form, and although the post-money version replaced it for new rounds, it still shows up on real cap tables. Founders who raised before 2018, or who reopened an old SAFE round at parallel terms, may have pre-money SAFEs sitting unconverted. They convert differently: a pre-money SAFE measures its ownership against the valuation before other SAFEs and the option pool are counted, so two pre-money SAFEs at the same cap end up owning slightly more, combined, than the cap arithmetic suggests.

For a founder choosing an instrument today this matters in one specific way. If you already hold pre-money SAFEs and are about to add post-money SAFEs, the conversion interaction is genuinely confusing and worth modeling with counsel — mixing the two forms is one of the few SAFE situations where a lawyer earns their fee. If you are starting clean, use the post-money form; there is no founder-side reason to issue a new pre-money SAFE in 2026.

SAFE Valuation Cap: Setting a Number You Can Live With

The SAFE valuation cap is the most consequential single number in the instrument — more than the discount, more than the MFN clause. The cap is the ceiling: no matter how high the next priced round prices, the SAFE converts as if the company were worth no more than the cap. At conversion the SAFE takes whichever produces the lower price per share — the cap-implied price or the round price reduced by the discount.

Here is the trap founders miss. A post-money SAFE cap is a post-money valuation. A priced round’s headline number is usually a pre-money valuation. If a founder negotiates a SAFE cap equal to the priced round’s pre-money, the SAFE actually converts at a worse price than the round itself, because the round’s post-money is pre-money plus new cash. The practical rule: a SAFE only protects founder equity better than a priced round when the cap is set comfortably above the round’s eventual post-money — and the further below that line the cap sits, the more a priced round starts to look like the founder-friendly choice. This calculator surfaces exactly that crossover.

SAFE vs Priced Round: When to Skip the Convertible Entirely

The SAFE vs priced round decision is the one most founders actually agonize over, because the convertible note has quietly lost relevance and the live choice is between a SAFE and priced preferred. The honest answer for sub-$1.5M rounds is: take the SAFE. It closes in about a week, costs around $1,500, and asks nobody to negotiate board seats. The priced round vs SAFE timeline gap alone — roughly 60-plus days versus seven — settles it for any founder who is close to running out of cash.

The case for a priced round strengthens as three conditions appear together: the raise crosses $1.5M and heads toward $3M, a single anchor investor wants protective provisions and a board seat, and the legal budget can absorb $25,000 to $50,000. At that point the priced round’s advantages — a single class of stock, no SAFE stack to untangle at Series A, and terms the next investor can diligence quickly — start to outweigh its cost and slowness. The crossover is rarely about dilution in isolation; it is about whether a clean cap table is worth the time and the legal bill.

The tool models this honestly: with neutral preferences a SAFE wins most rounds under $3M, and a priced round only wins when the founder explicitly weights a clean cap table and low dilution above speed and cost. That is the real-world answer — priced rounds are a deliberate trade, not a default.

The Y Combinator SAFE Document, Template, and Notes

Y Combinator publishes the SAFE note template for free, in five variants — a valuation-cap-only form, a discount-only form, a cap-and-discount form, an MFN (Most Favored Nation) form with no cap or discount, and a pro-rata side letter. The standing advice every startup lawyer repeats is the same: never draft your own SAFE. The yc safe note is a known quantity, and any deviation from the standard form costs the next round’s investor counsel billable hours to identify and price.

The MFN variant is the one founders most often misuse. An MFN SAFE has no cap and no discount on its own — instead it inherits the best terms of any SAFE the company issues later. Stack several MFN SAFEs and then issue one aggressive cap-and-discount SAFE, and every MFN holder ratchets up to that aggressive term at conversion. A founder planning multiple closes should track the worst-case MFN basket, not the per-SAFE cap.

One vocabulary note for clarity: a SAFE is not technically an "agreement" in the contract sense people expect, even though the safe agreement phrasing is common — SAFE stands for Simple Agreement for Future Equity. Once you have decided a SAFE is the right instrument here, our SAFE Note Calculator runs the cap, discount, and MFN conversion math on your specific numbers.

How This Decision Engine Scores Each Instrument

Each instrument is graded on six dimensions. Cost is the inverse of legal spend against your budget: a SAFE is modeled at about $1,500 plus $750 per SAFE already on the books, a convertible note at roughly $5,000, and a priced round at $18,000 plus 0.5% of the raise. Speed inverts days-to-close against your available timeline — a SAFE closes in about a week, a note in about two, a priced round in 60-plus days. Founder Dilution converts the equity each instrument costs you into a 0–100 score where 25 percentage points of dilution scores zero.

The other three dimensions are structural. Investor Friendliness rewards the priced round (95, or 100 with an anchor) over the note (80) over the SAFE (60). Optionality rewards the SAFE (90) over the note (70) over the priced round (50). Future-Round Readiness rewards the clean priced cap table (95) and penalizes a SAFE stack of more than four (dropping it from 85 to 50). The composite weights Founder Dilution at 25%, Cost at 20%, and Speed, Optionality, and Future-Round Readiness at 15% each, with Investor Friendliness at 10%.

The three founder preference sliders then re-weight that composite. Moving the cost-vs-dilution slider toward dilution lifts the Founder Dilution weight and cuts the Cost weight; the speed-vs-cleanliness slider trades Speed against Future-Round Readiness and Investor Friendliness. This is why the same $2.5M raise can recommend a SAFE for a speed-focused founder and a priced round for one who has decided a clean cap table is worth the legal bill — the math does not change, your priorities do.

Frequently Asked Questions