The short answer
With a post-money SAFE, the investor's ownership at conversion equals investment divided by the post-money cap: $500,000 at a $5,000,000 cap is 10%. Add up all SAFEs, then multiply every holder by one minus the seed round's percentage to see post-seed ownership. Model option pool increases separately, and remember discounts and uncapped SAFEs depend on the next round's price.
- Post-money SAFE ownership = investment ÷ post-money cap.
- SAFEs stack: add every SAFE's percentage to see what you've sold.
- At a priced round, multiply existing stakes by one minus the new investors' share.
- An option pool increase before the seed round usually comes out of founders' stakes.
- Uncapped and pre-money SAFEs need scenario modeling; the simple formula doesn't apply.
How to use this calculator
This is a worksheet you can run in your head, on paper or in any spreadsheet to see how much of your company a SAFE will cost. It covers the standard post-money SAFE, the form most pre-seed rounds use today, and shows how several SAFEs stack and what happens at your next priced round. Copy the formulas into a sheet, enter your own numbers in the cells marked "input", and model a few scenarios before you agree on a cap.
It's a planning tool, not legal or tax advice. Your actual conversion depends on the exact documents you sign. For background, read SAFE vs convertible note vs priced round and the glossary entries for SAFE, valuation cap and discount rate.
The core formula (post-money SAFE)
With a post-money valuation cap, the investor's ownership at conversion, before the new priced-round money, is simply:
SAFE ownership = Investment ÷ Post-money valuation cap
That's what makes post-money SAFEs easy to model: a $500,000 SAFE at a $5,000,000 post-money cap converts into 10% of the company's capitalization just before the priced round (when the round prices at or above the cap). Several SAFEs add up: each one's percentage is its own investment divided by its own cap.
Quick ownership table
| Investment (input) | Post-money cap (input) | Ownership at conversion |
|---|---|---|
| $100,000 | $5,000,000 | 2.0% |
| $250,000 | $5,000,000 | 5.0% |
| $500,000 | $5,000,000 | 10.0% |
| $500,000 | $8,000,000 | 6.25% |
| $1,000,000 | $8,000,000 | 12.5% |
| $1,000,000 | $10,000,000 | 10.0% |
| $1,500,000 | $12,000,000 | 12.5% |
Spreadsheet setup
Put each SAFE on its own row: column A investor, column B investment, column C post-money cap.
- Ownership per SAFE (column D): =B2/C2
- Total SAFE ownership: =SUM(D2:D20)
- Founders and pool after SAFEs convert: =1-SUM(D2:D20)
- After a priced round selling X% (input in F1): each holder's stake × (1 − F1)
Worked example: two SAFEs, then a seed round
Hypothetical example, simplified: no option pool increase at the seed round, and the seed price is above both caps.
- Founders and the option pool start at 100%.
- Pre-seed: an angel invests $300,000 at a $6,000,000 post-money cap → 5.0%. A micro-VC invests $450,000 at the same cap → 7.5%. Total SAFEs: 12.5%.
- When the seed round prices, the SAFEs convert first: founders and pool hold 87.5% of the pre-money company, SAFE holders 12.5%.
- Seed investors buy 20% of the post-money company. Everyone else is multiplied by 0.8.
| Holder | After SAFEs convert | After 20% seed round |
|---|---|---|
| Founders and option pool | 87.5% | 70.0% |
| Angel SAFE | 5.0% | 4.0% |
| Micro-VC SAFE | 7.5% | 6.0% |
| Seed investors | — | 20.0% |
| Total | 100% | 100% |
In practice, seed investors often ask for the option pool to be enlarged before their money comes in. That increase comes out of the pre-money holders, mainly founders, and can take several more points. Model it with a separate row.
Discounts, uncapped SAFEs and MFN
- Cap and discount. If a SAFE has both, it converts at whichever gives the investor the lower price per share: the cap price or the round price minus the discount. A 20% discount means the investor pays 80% of the round's price.
- Discount only, no cap. The investor's stake depends on the next round's price, so you can't know it in advance. Model a low, middle and high valuation.
- Uncapped MFN SAFE. Converts on the best terms you give later SAFE investors, or at the round price. Some accelerators use this form.
- Pre-money SAFE. An older form whose percentage moves as you raise more SAFEs. The simple formula above doesn't apply; ask your lawyer to model it.
If the priced round comes in below the cap
When the priced round's valuation is lower than a SAFE's cap, the cap doesn't bind, and the SAFE converts at the round price (or the discounted price if there's a discount). The investor then gets less than Investment ÷ Cap. For example, a $500,000 SAFE with no discount converting in a round priced at $4,000,000 post-money gets roughly what a new $500,000 investor would get at that price, not 10%.
Before you agree on a cap
- Add up every SAFE you've signed or plan to sign; total them as a percentage.
- Model the next priced round, including a likely option pool increase.
- Check founders' combined stake after seed; investors will too (cap table basics).
- Keep caps consistent within a round where you can; MFN clauses can force it anyway.
- Read the signed documents; they control, not this worksheet.
Frequently asked questions
How do I calculate dilution from a post-money SAFE?
Divide the investment by the post-money valuation cap. A $500,000 SAFE at a $5,000,000 post-money cap converts into 10% of the company before the next round's new money.
What happens to SAFEs at a priced round?
They convert into shares, usually just before the new investors buy in, and then everyone, including the converted SAFE holders, is diluted by the new round.
How does a discount work?
The investor converts at a discount to the round's price, such as 80% of it for a 20% discount, or at the cap price if that's lower.
Is this calculator legal advice?
No. It's a planning worksheet. Your signed documents control the actual conversion; have a lawyer review them.