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Convertible Note & SAFE Calculator
See how a SAFE or convertible note turns into shares at the next priced round. Enter the investment, valuation cap, discount and (for notes) interest, plus the round's share price and the company's share count, to get the conversion price, number of shares and ownership percentage.
Last updated:
Instrument
Investment terms
$
$
0 or empty = no cap.
%
0 = no discount.
% / yr
months
Priced round
$
Price new investors pay (Series A / seed preferred).
$
Optional: used for ownership after the round.
Enter your values to see the result.
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How to use the Convertible Note & SAFE Calculator
- Choose the instrument: post-money SAFE, pre-money SAFE or convertible note.
- Enter the investment, valuation cap and discount. For a note, add the interest rate and months outstanding.
- Enter the priced round: price per share and the company's fully diluted shares before the round.
- Optionally add the new money raised to see ownership after the round.
- Read the shares and ownership, then compare outcomes at other round prices in the table.
SAFE and convertible note conversion formulas
- Discount price = round price per share × (1 − discount)
- Cap price, pre-money SAFE or note = valuation cap ÷ pre-round fully diluted shares
- Cap price, post-money SAFE = post-money cap ÷ (pre-round shares + the SAFE's own shares). Solving gives SAFE shares = investment × pre-round shares ÷ (cap − investment).
- Conversion price = the lowest of cap price, discount price and round price
- Shares = converting amount ÷ conversion price (for a note, the amount includes accrued interest)
- Ownership after the round = conversion shares ÷ (pre-round shares + conversion shares + new investor shares)
Example (default inputs): $250,000 post-money SAFE, $8M cap, 20% discount, round at $2.50 with 5,000,000 shares. Cap shares = 250,000 × 5,000,000 ÷ 7,750,000 = 161,290, a cap price of $1.55; the discount price is $2.00, so the cap applies. After $3M of new money (1,200,000 shares) the SAFE holder owns about 2.54%.
SAFE vs. convertible note at a glance
| Feature | Post-money SAFE | Pre-money SAFE | Convertible note |
|---|---|---|---|
| Legal form | Contract right to future equity | Contract right to future equity | Debt that converts to equity |
| Interest | None | None | Accrues, usually converts |
| Maturity date | None | None | Yes, often 12-36 months |
| Cap measured on | Capitalization including SAFEs | Capitalization before SAFEs | Usually pre-money capitalization |
| Who bears SAFE dilution | Existing holders (founders) | Shared with SAFE holders | Shared with note holders |
| Ownership known at signing | Yes (investment ÷ cap) | No | No |
Things to check in your documents
- Definition of capitalization: whether the unissued option pool and any pool increase in the round are included changes the cap price.
- Multiple SAFEs or notes: with post-money SAFEs, each investor's percentage is fixed, so stacking several SAFEs dilutes founders more than it may seem.
- MFN and pro-rata side letters can change terms or give the right to invest more in the round.
- Dissolution or sale before a round: SAFEs and notes usually return the investment or convert at the cap in an acquisition; this calculator covers the priced-round case.
Frequently asked questions
How does a SAFE convert into shares?
At a priced round, the SAFE converts at the lower of the cap price (valuation cap ÷ company capitalization) and the discount price (round price × (1 − discount)). Shares = investment ÷ conversion price. If neither is lower than the round price, it converts at the round price.
What is the difference between a pre-money and post-money SAFE?
A pre-money SAFE's cap is divided by the shares before the SAFEs convert, so several SAFEs dilute each other and the founders. A post-money SAFE (the Y Combinator standard since 2018) includes the SAFE shares in the capitalization, so the investor's ownership before new money is fixed at investment ÷ post-money cap, e.g. $250,000 ÷ $8M = 3.125%.
How does interest on a convertible note work?
Notes accrue interest, usually simple interest of 2% to 8% a year, which is not paid in cash but added to the amount that converts. A $100,000 note at 8% for 24 months converts $116,000 into shares.
Do the cap and discount both apply?
No. When a SAFE or note has both, the investor gets whichever gives the lower price per share (more shares). The table of other round prices shows where the cap stops being better than the discount.
What is the effective conversion valuation?
It is the conversion price multiplied by the company's shares after conversion. It shows the valuation the investor effectively bought in at, which is at or below the cap when the cap applies.
Is this the exact number of shares a lawyer will calculate?
It is a close estimate. Real conversions depend on the exact definitions in your documents (company capitalization, which options and pool increases are included, rounding, multiple SAFEs converting together and pro-rata rights). Use it for planning and confirm with your cap table and legal counsel.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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