Key takeaways
- A SAFE converts at the lowest of three prices: the cap price, the discount price and the round price. Lowest price means most shares for the holder.
- On a post-money SAFE that converts at its cap, the holder owns the amount divided by the cap, measured just before the new money comes in.
- Post-money SAFEs don't dilute each other, but they are diluted by the new investors and by any option pool increase made in the round.
- The SAFEs sit inside the pre-money, so the round price depends on how many shares they convert into. The tool solves that loop for you.
- The result is an estimate for planning and checking. The signed documents and your lawyer decide the real numbers.
How to use the SAFE conversion calculator
- 1Pick the currency, then enter the fully diluted shares before the round: issued shares, granted options and the unissued pool. Leave the SAFEs out of this number.
- 2Enter the priced round: the pre-money valuation, the new money and, if the investors ask for one, the option pool increase as a share of post-round shares.
- 3Add each SAFE with its amount, type (post-money or pre-money), valuation cap and discount. Leave the cap empty for an uncapped SAFE.
- 4Read the round price, how each SAFE converts and the ownership split after the round. Notes explain anything unusual, such as a SAFE converting at the round price.
- 5Open "Show the formula with your numbers" to check each step, then copy the summary into your notes or an email to your lawyer.
How a SAFE converts at a priced round
Y Combinator's SAFE user guide sets out the mechanics. When the priced round (the Equity Financing) closes, each SAFE converts into preferred shares. The holder gets whichever price gives more shares: the Safe Price (the valuation cap divided by the Company Capitalization), the Discount Price (the round price times one minus the discount) or the round price paid by the new investors.
For a post-money SAFE, the Company Capitalization counts issued shares, options, the unissued pool and the shares that all SAFEs and other convertibles turn into. It leaves out the pool increase made in the round. That is why, at its cap, a post-money SAFE owns exactly its amount divided by the cap just before the new money. YC's quick-start example: $1 million at a $6.7 million post-money cap is about 15%.
For a pre-money (original) SAFE, the Company Capitalization includes the pool increase and leaves out the SAFEs, so the cap price is the cap divided by existing shares plus the pool increase.
| Step | Formula |
|---|---|
| Round price | Pre-money valuation ÷ (existing shares + SAFE shares + pool increase) |
| Cap price, post-money SAFE | Cap ÷ (existing shares + all SAFE shares) |
| Cap price, pre-money SAFE | Cap ÷ (existing shares + pool increase) |
| Discount price | Round price × (1 − discount) |
| SAFE shares | Amount ÷ the lowest of the prices that apply |
| New investor shares | New money ÷ round price |
| Pool increase | Pool increase % × post-round shares |
The SAFE shares appear in the round price and the round price appears in the discount price, so the tool repeats the sum until the numbers stop changing. It usually settles in a few steps.
A worked example with two SAFEs
Northwind Robotics, a fictional company, has 9,000,000 fully diluted shares. It raised two post-money SAFEs: $1,000,000 from an angel at a $10 million cap with no discount, and $500,000 from a seed fund with a 20% discount and no cap. It now raises $5 million at a $20 million pre-money valuation, and the new investors want a 10% option pool increase. These numbers are filled in when the tool loads.
| Holder | Price per share | Shares | Ownership after the round |
|---|---|---|---|
| Existing holders | 9,000,000 | 60.5% | |
| Angel SAFE, converts at the cap | $0.9603 | 1,041,322 | 7% |
| Seed fund SAFE, converts at the discount | $1.3444 | 371,900 | 2.5% |
| Option pool increase | 1,487,603 | 10% | |
| New investors | $1.6806 | 2,975,206 | 20% |
| Total | 14,876,033 | 100% |
The angel owns 10% just before the round ($1 million ÷ $10 million), as the post-money cap promises. The round then dilutes that to 7%. The seed fund pays 80% of the round price. The post-money valuation is the $20 million pre-money plus the $5 million raised.
Post-money or pre-money SAFE: what changes?
YC's documents page says it standardised on the post-money SAFE in 2018. With a post-money SAFE, founders and investors can see the ownership sold at signing, because each SAFE's share at its cap is its amount divided by the cap. Raising more on SAFEs dilutes the founders, not the earlier SAFE holders.
With pre-money SAFEs, the SAFEs dilute each other and the pool increase is counted before they convert, which moves dilution from the founders to the SAFE holders. Many older companies still have pre-money SAFEs on their cap table, so the tool lets you mix both types.
- Uncapped SAFE with no discount (often called an MFN SAFE): it converts at the round price, like the new investors. If its most favoured nation clause picked up better terms from a later SAFE, enter those terms instead.
- Round below the cap: the round price is lower than the cap price, so the holder converts at the round price and gets more shares than the cap would give.
- Too much raised: if post-money SAFE amounts add up to the cap or more, the SAFEs would own the whole company. YC's guide calls this out, and the tool refuses those inputs.
Limits of the calculator
- It's an estimate, not legal, tax or financial advice. Real conversions round share counts, and documents can define the pool, the Company Capitalization or the discount differently.
- It covers SAFEs only. Convertible notes add interest and maturity terms, and side letters such as pro rata rights change later rounds, not this conversion.
- It treats the option pool increase as a share of post-round shares, which is the common way term sheets state it. If yours names a share count, convert it first.
- It doesn't model liquidation preferences or what each holder receives in a sale. For ownership across several rounds, use the cap table dilution calculator.
Where Delsivo fits
Delsivo is an investment workspace for venture funds, not a cap table tool. In the pilot, a fund can send a founder a follow-up form from a template, including one for the cap table, and keep the answer on the deal record next to the deck and the fund's thesis. You don't need Delsivo to use this calculator, and nothing you type here reaches it. See how Delsivo works.
Sources
- Y Combinator: Safe financing documents (checked 6 November 2026)
- Y Combinator: Post-Money Safe User Guide (PDF) (checked 6 November 2026)
Facts about other companies and services come from the pages listed, on the dates shown, and can change.