How to use this SAFE calculator
- Enter today's cap table. Your founders' shares, options already granted or promised, and the unissued shares left in your option pool. Your cap table software shows all three.
- Add each SAFE in the order you issued it, with the investment, valuation cap and discount. Choose post-money for SAFEs on Y Combinator's standard form since 2018, and tick MFN for an uncapped SAFE with a most favored nation clause.
- Describe the priced round: the pre-money valuation, how much new money it raises and the option pool the new investors want afterwards.
- Read the results. You'll see your ownership after the round, each SAFE's conversion price and shares, and the full pro forma cap table. Copy a share link or download a CSV for your co-founders or lawyer.
Type amounts the way you'd say them: 500k or 1.5m both work.
How a SAFE converts into shares
A SAFE (simple agreement for future equity) isn't stock when you sign it. It converts into preferred shares at your next priced round, at the lowest of up to three prices:
- Cap price: the valuation cap divided by the company's capitalization just before the round
- Discount price: the round price minus the SAFE's discount
- Round price: what the new investors pay per share
SAFE shares = investment ÷ lowest of (cap price, discount price, round price)
For a post-money SAFE, Y Combinator defines the capitalization ("Company Capitalization") as every share, granted and promised option, the unissued option pool and every SAFE and note converting in the round. It leaves out the round's new money and any option pool increase made for the round. Because the SAFEs themselves are counted, a post-money SAFE's ownership is simple:
Ownership right before the round = investment ÷ post-money valuation cap
$500k on a $5M post-money cap is 10%, however many other SAFEs you raise. The priced round's new money and pool increase then dilute that 10% along with the founders' stake.
Worked example: two SAFEs converting in a Series A
This is Example 1 from Y Combinator's Post-Money Safe User Guide, and it's preloaded in the calculator above. The founders hold 9,250,000 shares, 650,000 options are granted or promised and 100,000 sit unissued in the pool, so there are 10,000,000 fully diluted shares. Investor A bought a $200,000 SAFE with a $4M post-money cap and Investor B an $800,000 SAFE with an $8M post-money cap. The company then raises a $5M Series A at a $15M pre-money valuation, with a 10% available option pool afterwards.
- SAFE ownership at the caps: A owns $200k ÷ $4M = 5% and B owns $800k ÷ $8M = 10%, so the SAFEs hold 15% between them.
- Company Capitalization: 10,000,000 ÷ (100% − 15%) = 11,764,706 shares. A gets 5% of that, 588,235 shares, at $0.3400 each. B gets 1,176,471 shares at $0.6800.
- Option pool increase: 1,694,570 new shares make the available pool 10% of the company after the round.
- Series A price: $15,000,000 ÷ (11,764,706 + 1,694,570) = $1.1145 per share.
- New money: $5M ÷ $1.1145 = 4,486,425 shares, which is 25% of the company ($5M ÷ $20M post-money).
| Shareholder | Shares | Ownership |
|---|---|---|
| Founders | 9,250,000 | 51.54% |
| Options granted | 650,000 | 3.62% |
| Available option pool | 1,794,570 | 10.00% |
| Investor A | 588,235 | 3.28% |
| Investor B | 1,176,471 | 6.56% |
| Series A investors | 4,486,425 | 25.00% |
Investor A ends with 3.28% and Investor B with 6.56%: both diluted from 5% and 10% by the new money and the pool increase. Y Combinator's guide rounds the pool increase to 1,695,000 shares and the price to $1.1144, so its share counts differ from these by less than 0.1%.
Post-money vs pre-money SAFEs
Y Combinator switched its standard SAFE from pre-money to post-money in 2018. Both convert at the cap divided by a share count. The difference is which shares are counted:
| Included in the share count | Pre-money SAFE | Post-money SAFE |
|---|---|---|
| Outstanding shares and options | Yes | Yes |
| Promised options | Yes | Yes |
| Unissued option pool | Yes | Yes |
| Option pool increase in the priced round | Yes | No |
| SAFEs and convertible notes | No | Yes |
With pre-money SAFEs, every new SAFE dilutes the earlier SAFE holders as well as the founders, and nobody knows the final split until the round is priced. With post-money SAFEs, each investor's percentage is locked in at investment ÷ cap, and the founders absorb the dilution from later SAFEs. Switch a SAFE's type in the calculator to compare the two on your own numbers.
Valuation cap, discount and MFN explained
- Valuation cap: the highest valuation the SAFE converts at. A post-money cap includes the SAFE money itself; a pre-money cap doesn't.
- Discount: a percentage off the price new investors pay, for example 20%. A SAFE with only a discount (no cap) always converts at the discounted round price.
- Cap and discount together: the investor gets whichever price is lower, never both.
- Most favored nation (MFN): an uncapped SAFE that can adopt better terms from SAFEs issued after it. The calculator checks every later SAFE and note and applies the terms that give the MFN holder the most shares.
- Rounds priced below the cap: the SAFE converts at the round price, so it ends up with more than investment ÷ cap.
Raising on convertible notes instead? The convertible note calculator adds interest and pre-money caps. To see dilution across several rounds, use the equity dilution calculator.
How the calculator works
- Post-money SAFEs use Y Combinator's Company Capitalization, and pre-money SAFEs use the pre-money share count from the table above. Notes with a pre-money cap are treated like pre-money SAFEs.
- The option pool target is the unissued pool after the round as a share of all fully diluted shares. The increase is part of the pre-money, which is how most term sheets are written.
- SAFE shares, the pool increase and the price all depend on each other, so the calculator solves them together to an exact answer rather than estimating. Shares are shown rounded to whole numbers; real cap tables round each investor down, so expect differences of a share or two.
- We test the math against all of the priced-round examples in Y Combinator's user guide, including a round priced below a cap and a mix of pre-money and post-money SAFEs.
- Not modeled: pro rata side letters, a sale of the company before the round, and liquidation preferences.