Founder Toolkit · Step 2

SAFE Calculator for Founders & Angel Investors

Plug in your SAFE amount and the valuation cap. See what you own today, what you own after each future round (Priced Seed, Series A), and what it could mean at exit.

Y Combinator post-money SAFE math Cap only Multi-stage dilution path Carta Q2 2026 medians
i What is a SAFE? A 90-second primer for founders and angel investors ▾

SAFE stands for Simple Agreement for Future Equity. It's a one-document investment instrument created by Y Combinator in 2013 that lets early-stage startups raise money quickly without negotiating a formal valuation up front. Today, post-money SAFEs are roughly ~90% of all pre-seed and seed-stage instruments in the US (per Carta data) — they have effectively conquered the early-stage fundraising market.

Why it exists: before SAFEs, early-stage rounds were either priced (full term sheet, lawyers, weeks of negotiation, expensive legal fees) or done with convertible notes (debt with interest and a maturity date — fiddly for both sides). The SAFE replaced both with a 5-page document that's free to use, fast to sign, and avoids the awkwardness of pricing a company that may not even have a product yet.

How it works: you give the company $X today. You don't get shares yet. Instead you get the right to receive shares in the future, when the company does its next priced equity round (Series Seed, Series A, etc.) — at terms that reward you for taking the early risk. Two main mechanisms can apply:

  • Valuation cap: the maximum company valuation at which your SAFE will convert. If the future round prices the company at $30M but your cap is $5M, your SAFE converts as if the company were worth $5M — so you get more shares for your money.
  • Discount: a percentage off the future round's price (typically 10–20%).

Some SAFEs use a cap, some use a discount, many use both (the better of the two applies at conversion).

Pre-money vs post-money: YC introduced the post-money SAFE in 2018. The post-money version locks in your ownership percentage at signing — you know exactly what you bought. (The original pre-money version had a recursive math issue where adding more SAFEs diluted the existing ones unpredictably.) This calculator models the YC post-money SAFE.

Two more options you may see:

  • MFN (Most-Favored Nation) clause: gives you the right to upgrade your SAFE's terms if the company later issues another SAFE on better terms.
  • Pro-rata side letter: gives the investor the right to invest more money in the next priced round to maintain their ownership %.

This calculator models the standard YC post-money SAFE template with a valuation cap only. Discount, MFN, and pro-rata aren't modeled here. For the official YC docs and explanations, see the YC Post-Money SAFE User Guide (Feb 2023).

Your SAFE
Enter the dollar amount you're investing or raising, and the valuation cap on this SAFE.
$
Total dollars going into this SAFE.
$
The maximum company valuation at which your SAFE will convert to shares at the priced round.
Median caps vary a lot by sector, so this sharpens the benchmark below.
Do you have any previous SAFEs?
If the company has already executed earlier SAFEs, add them here (amount and cap for each). The calculator stacks their dilution with the SAFE above so you see the company's total SAFE exposure. Went through an accelerator? Pick it below and its standard instruments drop in, including MFN SAFEs: those fix no ownership at signing and later adopt the most favourable cap the company grants to any SAFE issued afterwards (yours included), falling back to the priced-round price only if there is none.
How much will the company raise in total before exit?
Slide to set the lifetime raise, or type an exact figure straight into the box. Each band maps to a real round (medians from our Carta Q2 2026 guide) and stacks the dilution accordingly.
Company type:
$M total raised
→ Pre-Seed + Seed + Series A
Drag the slider, or click the number above to type an exact amount
●
Angel + Pre-Seed
SAFE · raises up to ~$2M
○
+ Seed
SAFE or priced · raises ~$2–6M
○
+ Series A
Priced · raises ~$6–20M
○
+ Series B
Priced · raises ~$15M+
Why $15M as the default for Traditional SaaS? Where does this come from?

The default is what a Traditional SaaS company has typically raised in total by the time it closes a Series A: Round 1 angel and pre-seed SAFEs ($1.5M) plus the Seed ($3.3M) and Series A ($9.8M) medians, landing at about $15M. Carta puts median cash raised at $3.3M for a non-AI seed versus $4.5M for an AI seed, and $9.8M versus $15M at Series A, so AI-heavy companies raise more at every stage. Source: Carta AI vs non-AI analysis, Oct 2025 to Mar 2026 (1,188 priced rounds). Cross-check by a different method: Carta's cohort tracking of 4,369 startups founded in 2018 found the median funded company that reached Series A ended with roughly $16M in total lifetime fundraising, around $22M for AI companies. Two methods, same answer. Sources: Carta State of Private Markets 2025, PitchBook-NVCA Q2 2025.

OR set up each round yourself
⚙ Edit Carta medians & add or remove rounds advanced
These rounds and the slider above stay in sync both ways: the slider's total raised equals the sum of every round you check here. Drag the slider and the priced-round raises redistribute; edit a raise or toggle a round and the slider follows. Round 1 is YOUR SAFE round: your SAFE plus any other money raised alongside it at the same cap. Earlier SAFEs added above (accelerator or prior angels) are separate prior rounds, each counted at its own cap; they appear as their own line in Round 1 and in the lifetime total. Both stay fixed; the slider only redistributes the priced rounds.
Linked to your SAFE above
Carta AI vs non-AI · P50
Carta AI vs non-AI · P50
Carta AI vs non-AI · P50
What you own
Your share at SAFE signing is the post-money guarantee. Each priced round dilutes you further.
Math model:
The post-money SAFE in plain English: you lock in your percentage post-conversion of all SAFEs but pre-priced round — so other SAFE-holders don't dilute you. But you are diluted by every priced round, including the one that triggers your conversion. That's the logic baked into the SAFE.
Cap vs Market Median ⓘ
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of tier median
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Key insight

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Send this scenario The link opens the calculator on these exact numbers — amount, cap, industry and company type — so they see the same verdict you do.
Where your cap sits in the market
At SAFE signing
0.40%
Your post-money SAFE claim — the share you'd get if the priced round converted at your cap.
After Series A (final modeled stage)
0.22%
Your share after all checked priced rounds dilute you.
On a $67,000,000 post-money basis, your stake is worth $147,400.
Cap table snapshot (after Series A)
How the cap table splits at the end of all checked priced rounds.
Stakeholder Share
Take this cap table into Excel
A pro forma of the table above: every SAFE’s conversion, the price per share, the option-pool increase and the post-financing ownership, as live formulas you can edit. Your working document, not something to send an investor.
"Existing shareholders" = founders, advisors, and early employees holding stock before any of these rounds. Pool top-ups create fresh employee equity that dilutes everyone except the new investors of that round.
What it could mean at exit
Illustrative only. Returns assume the SAFE's ownership after the final modeled round stays intact through to exit. Any rounds beyond the last checked stage (Series B, C, …) will dilute it further.
Exit at $50M
$146,667
7.3x return on $20,000 invested
Exit at $100M
$293,333
14.7x return on $20,000 invested
Exit at $500M
$1,466,667
73.3x return on $20,000 invested
Real returns are typically lower than this because of liquidation preferences and any further rounds (Series B, C, growth) beyond your last modeled stage. This is still a simplified view.
Get this scenario as a PDF report

A 5-page report tailored to your inputs — cover page with your reasonableness score, deal summary, ownership & dilution waterfall, exit returns, and our full methodology with sources. Sent to your inbox in seconds. Free.

Share this summary with the other side of the table
How the math works 
Your share at SAFE signing = SAFE amount ÷ Cap
Per the YC Post-Money SAFE User Guide: your SAFE locks in S ÷ Cap of the company post-conversion of all SAFEs but pre-issuance of the new priced-round investors. You are protected from dilution by other SAFEs converting alongside yours and by any pool grants made between the SAFE round and the priced round.
At the first priced round (SAFE conversion):

  ▸ ACCURATE (per YC SAFE User Guide — default):
       SAFE share = (SAFE ÷ Cap) × (1 − New investors% − Pool top-up%)
       New investors% = Raise ÷ (Pre-money + Raise)
       The SAFE is diluted by both the new money AND
       the pool top-up adopted as part of the round —
       like any other existing shareholder.

  ▸ SIMPLIFIED (matches YC's online simulator):
       Your share = SAFE ÷ Cap
       You take no dilution at this round;
       founders absorb both the new money AND the pool.
Both versions agree on the spirit of the post-money SAFE: your % is locked in at S ÷ Cap of the post-SAFE / pre-priced-round company. They differ on what dilutes you at the priced round itself. The Accurate version (per the User Guide, page 4 and Note #2 on page 2) says: "the safes are like their own round, which means they are diluted by the Series A (just like everyone else)". The Simplified version (YC's online simulator) keeps the SAFE locked through the round and pushes all dilution onto the founders — a few basis points generous. Toggle Math model above the results to switch.
At each later priced round (Series A, B, …):
   Dilution factor = 1 − New investors% − Pool top-up%
   Everyone existing × Dilution factor
   New investors + pool added on top
Once your SAFE has converted to preferred shares at the first priced round, you're treated like any other preferred shareholder for subsequent rounds. Both the new money and the pool top-up dilute you proportionally.
This calculator uses the YC post-money SAFE math as commonly applied in cap-table modeling: SAFE % is fixed relative to the pre-new-money capitalization (including pool top-up) and is then diluted by the new investors' money. If a priced round's pre-money ends up below your cap, the SAFE would convert at the priced-round price instead of the cap — this calculator always uses your cap, the typical case. Liquidation preferences, anti-dilution provisions, and any rounds beyond the last enabled stage would further reduce your exit return.
This calculator models post-money SAFEs with a valuation cap only, chained through a Priced Seed and an optional Series A using Carta Q2 2026 medians. Discount rates, prior priced rounds, liquidation preferences, anti-dilution provisions, and any rounds beyond Series A are not modeled.

For informational purposes only. Not legal or financial advice.
Numbers updated

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