SAFE Note Calculator

A SAFE — Simple Agreement for Future Equity — is the contract that has quietly become the default way early-stage startups raise money. Introduced by Y Combinator in 2013 and redesigned as the "post-money SAFE" in 2018, it lets an investor give a startup cash today in exchange for the right to receive shares later, when the company raises a priced equity round. There is no interest rate, no maturity date, and no valuation negotiation at the moment of investment — which is exactly why founders and angels love it. In the last few years SAFEs have gone from a Silicon Valley curiosity to the standard instrument for pre-seed and seed funding worldwide, and understanding what they actually cost you in ownership has become a core founder skill.

The catch is that a SAFE's price is deferred, not absent. The two levers that determine how much equity a SAFE eventually converts into are the valuation cap and the discount. Both exist to reward the SAFE investor for taking risk earlier than the priced-round investors, and both directly determine how much of your company you are giving away — you just don't see the number until the conversion happens. That delay is where founders get surprised: a few "small" SAFEs signed over eighteen months can quietly add up to 25% or more of the company converting all at once in the seed round.

This SAFE note calculator makes the deferred price visible before you sign. Model any combination of investment amount, cap, discount, and future round, and you'll see the exact ownership split between founders, the SAFE investor, and the new priced-round investor — so you can negotiate the cap with real numbers instead of gut feeling.

The calculator simulates the moment every SAFE is built for: conversion at the next priced round. When that round happens, the SAFE converts at the better of two prices for the investor — the price implied by the valuation cap, or the round price reduced by the discount. The calculator computes both routes, picks the one that gives the investor more ownership (exactly as the SAFE contract requires), and then applies the dilution from the new money coming into the round. The math behind the three bars you see above:

• ✓Discount route. The SAFE converts at the round's valuation reduced by the discount. A 20% discount on a $10M valuation means the SAFE investor buys in at an effective $8M.
• ✓Cap route. The SAFE converts as if the company were worth the cap, no matter how high the actual round valuation is. A $5M cap in a $15M round means the SAFE investor pays one third of the round price.
• ✓Best-of rule. The investor automatically gets whichever route produces the lower conversion price — the calculator shows you which one applied under "Conversion basis".
• ✓Round dilution. After conversion, everyone — founders and SAFE investor alike — is diluted by the new investor's stake, calculated as new investment divided by post-money valuation.

The "Effective valuation" tile shows the valuation your SAFE investor actually converted at, and "Effective discount vs. round" translates that into plain language: how much cheaper the SAFE investor's shares were compared to what the new investor paid in the same round. When the cap is far below the round valuation, this effective discount can be 50–70% — far more than the nominal discount printed in the contract. Seeing that number is usually the moment founders understand why the cap, not the discount, is the term worth negotiating hardest.

Like every serious SAFE dilution calculator, this one uses the standard simplified model: it ignores option-pool expansions, pro-rata side letters, and multiple SAFE tranches converting simultaneously. Those refinements shift the result by a few points at most in typical scenarios — the shape of the answer, and the negotiation insight, stay the same. Everything runs in your browser; nothing you enter is stored or sent anywhere.

The valuation cap is the maximum company valuation at which the SAFE converts into shares. It exists to protect the early investor from their own success: without a cap, an angel who wrote a check when the company was two people and a prototype would convert at the same price as a Series A investor who arrived after two years of de-risking. The cap fixes that by saying, in effect, "no matter how valuable the company becomes, my money buys shares as if the company were worth at most this much."

For founders, the cap is the single most expensive number in the agreement. Run the scenario in the calculator: $500,000 on a $5M post-money cap converts to 10% of your company — regardless of whether your seed round later prices you at $8M or $30M. If the round lands at $30M, that investor got shares at an 83% effective discount. That is not a flaw; it's the deal. But it means the cap should reflect a realistic valuation for your stage, not a defensive lowball number you accept because the money is on the table.

• ✓A quick sanity check for founders: divide the SAFE amount by the post-money cap. That quotient is the minimum ownership you're selling. $250k on a $2.5M cap = at least 10% gone.
• ✓A quick sanity check for angels: the cap is your worst-case entry valuation. If you wouldn't buy equity at the cap valuation today, don't sign the SAFE.
• ✓Uncapped SAFEs (discount only, or MFN-only) shift almost all risk to the investor and are rare outside of hot competitive rounds and party rounds with strong momentum.

Typical caps track the market for priced rounds at the same stage: pre-seed SAFEs commonly carry caps in the $3M–$10M range, seed-stage SAFEs $8M–$25M, with big variation by geography, sector, and traction. The honest way to set yours is to ask what a priced round would value you at today, and put the cap modestly above it.

The discount is the simpler of the two terms: it gives the SAFE investor a fixed percentage off the price the new investors pay in the priced round, typically 10–25% with 20% as the market norm. A 20% discount in a round priced at a $10M valuation means the SAFE converts as if the valuation were $8M. Unlike the cap, the discount scales with the round — it always delivers the same relative advantage, whether your round is small or huge.

When a SAFE has both a cap and a discount, the investor doesn't get both — they get whichever single route gives them the better price. The calculator applies this best-of rule automatically and labels the result. The practical pattern is easy to remember:

• ✓Company outperforms → round valuation far above the cap → the cap wins, and the effective discount can be enormous.
• ✓Company raises near or below the cap → the 20% discount beats the cap price → the discount wins, and the investor gets a modest, predictable advantage.
• ✓Break-even point: the discount route wins whenever the round valuation is below cap ÷ (1 − discount). With a $5M cap and 20% discount, that's any round priced under $6.25M.

This is why sophisticated founders spend their negotiating capital on the cap and concede the discount easily: in every scenario where your company does well, the discount is irrelevant and the cap sets the price. Slide the pre-money valuation in the calculator from low to high and watch the "Conversion basis" tile flip from Discount to Valuation cap — that flip point is where your upside starts flowing to the SAFE holder.

The original 2013 SAFE was "pre-money": the valuation cap referred to the company's value before the SAFE money (and any other SAFEs) were counted. That made each investor's final ownership depend on how many other SAFEs converted alongside theirs — nobody could compute their stake until the round closed. In 2018, Y Combinator replaced it with the post-money SAFE, where the cap includes the SAFE itself and all other converting SAFEs. The result: ownership becomes a simple, fixed fraction. $500k on a $5M post-money cap is exactly 10% immediately before the priced round, full stop.

That predictability is great for investors — and subtly expensive for founders, because under a post-money SAFE, SAFE holders don't dilute each other; only the founders absorb the dilution from every additional SAFE sold. Sell five post-money SAFEs of 4% each and you have given away exactly 20%, all of it from the founders' side of the table. Under the old pre-money structure, each new SAFE also diluted the earlier SAFE holders, softening the founders' hit.

• ✓Post-money SAFE: investor ownership = investment ÷ cap. Clean, fixed, and standard today. Founders bear 100% of the SAFE dilution.
• ✓Pre-money SAFE: investor ownership = investment ÷ (cap + all converting money). Slightly better for founders, but everyone's stake is uncertain until conversion.
• ✓Rule of thumb: with a post-money SAFE, always track the running total of investment ÷ cap across every SAFE you've signed. That sum is founder dilution you've already committed to.

Toggle between the two types in the calculator with identical numbers and you'll see the post-money SAFE hand the investor a visibly larger slice. Neither is "wrong" — but you should know which one you're signing, and price the cap accordingly.

Because SAFEs are so easy to sign — no lawyers negotiating share classes, no board mechanics, money in the bank in days — founders tend to raise on them continuously: $100k here, $250k there, a bridge SAFE before the seed. Each individual SAFE feels harmless. The danger is that none of them show up on your cap table until they all convert at once. This is the single most common unpleasant surprise in seed rounds, and it has a name: SAFE stacking.

The arithmetic is unforgiving. Say you raise $1.5M across post-money SAFEs at caps averaging $6M — that's 25% of the company committed. Your seed round then sells another 20% to the lead investor, and the round demands a 10% option pool. Founders who owned 100% eighteen months ago come out of the seed round below 50%, before a Series A has even happened. Investors see this pattern weekly; founders often see it for the first time in the pro-forma cap table their lead sends over, when it is too late to change anything.

• ✓Keep a running SAFE ledger: for every post-money SAFE, note investment ÷ cap. Keep the total under ~20% before your first priced round if you can.
• ✓Re-run this calculator before each new SAFE, treating all previously committed SAFE percentages as already gone from the founder bar.
• ✓Raise caps as you de-risk: your third SAFE, signed with revenue and users, should carry a meaningfully higher cap than your first one signed with a slide deck.
• ✓Model the option pool: priced rounds typically require a 10–15% employee pool created pre-money — dilution that also lands on founders, on top of everything the calculator shows.

None of this means SAFEs are bad. It means SAFEs move the accounting from signing day to conversion day — and the founders who win are the ones who do the accounting continuously instead of once, at the worst possible moment.

Founders comparing early-stage funding instruments usually choose between three structures, and the SAFE sits deliberately in the middle on complexity:

• ✓SAFE: not debt — it never accrues interest and never matures. The investor's only path to value is conversion (or a payout in an acquisition). Five pages, standardized, near-zero legal cost. The trade-off: investors hold a security with no enforceable deadline, which is why they insist on caps.
• ✓Convertible note: actual debt with an interest rate (typically 4–8%) and a maturity date (typically 18–24 months). It converts like a SAFE — cap and/or discount — but if no round happens before maturity, the investor can in principle demand repayment. More protective for investors, more dangerous for founders, still cheap to paper.
• ✓Priced equity round: shares sold at a negotiated valuation, with a shareholders' agreement, board seats, and investor rights. Full clarity and clean ownership from day one, at the price of weeks of negotiation and significant legal fees. Standard from seed or Series A onward.

The practical guidance most startup lawyers give: raise your first outside money on post-money SAFEs with sensible caps, switch to a priced round once you're raising roughly $2M or more or taking a lead investor who wants a board seat, and use convertible notes only when an investor specifically requires debt. Whichever instrument you choose, the ownership math in this calculator — money in, valuation reference, dilution out — is the constant underneath all three.

• ✓Treating the cap as a compliment instead of a price. A $10M cap doesn't mean your company is worth $10M — it means you're selling equity at up to that valuation. Do the division before celebrating.
• ✓Never adding up the stack. Each SAFE is signed in isolation; the dilution arrives together. Keep the running total of investment ÷ cap visible at all times.
• ✓Negotiating the discount while giving away the cap. In every good outcome the cap sets the price and the discount does nothing. Spend your leverage where the money is.
• ✓Confusing pre-money and post-money caps. The same $5M number is a materially different deal in the two structures. Check which template you're signing — today it's almost always post-money.
• ✓Forgetting the option pool. Your seed round will likely create a 10–15% employee pool before the new money — dilution on top of everything the SAFE math shows.
• ✓Modeling only the happy case. Run the down-scenario too: if your round prices below the cap, the discount route kicks in and the picture changes. Three scenarios take three minutes.