Why we picked it This is the modeling tool to actually stack your conversions before you sign, which is the whole opinionated answer. You enter each SAFE (pre-money or post-money, its cap, its discount) plus your fully diluted share count and a hypothetical priced-round valuation, and it converts every instrument at once and shows the founder and option-pool dilution that falls out. It handles the exact case founders get wrong: multiple SAFEs at different caps interacting, rather than a single clean instrument. Run it at several Series A valuations and you see the 15-point surprise before it happens instead of at the closing table. (Page was live but blocked our automated fetch, so verify the URL yourself.)
SAFE and Convertible Note Calculator
From Carta by Carta free tool
- Model the full stack of SAFEs converting together, not one SAFE in isolation, since low caps quietly enlarge each other's slices
- Pre-money and post-money SAFEs dilute differently: post-money guarantees the investor a fixed slice and pushes all the surprise onto founders and the pool
- Stress-test at multiple Series A valuations, because a lower priced round makes low-cap SAFEs convert into an even bigger share