SAFE Dilution Calculator

A Simple Agreement for Future Equity (SAFE) lets a startup take money now and figure out the price later — at the next priced round. The post-money SAFE (Y Combinator's current default, since 2018) fixes the SAFE holder's ownership as a share of the post-money valuation, not the pre-money. That changes the math meaningfully for founders.

This calculator illustrates how a single post-money SAFE converts at the next priced round. It pairs two conversion levers — valuation cap and discount — and applies whichever produces the more SAFE-holder-favorable outcome (more shares, more ownership).

How it works

• Valuation cap sets a ceiling on the price the SAFE holder pays. If the round prices the company above the cap, the SAFE converts as if the price were the cap. Below the cap, the cap doesn't bind.
• Discount is a percentage off the round price (e.g. 20% means the SAFE holder pays 80% of the round price per share). With no cap, the discount alone determines the conversion price.
• Both: the SAFE holder gets whichever is better for them. In practice, the cap binds when the company has appreciated meaningfully between the SAFE and the priced round.
• Option pool top-up: investors typically require a fully-diluted option pool of 10–15% before the round closes, carved out of the pre-money. This dilutes founders only — not the new investor.

What this calculator does not model

• Multiple SAFEs stacking (real life rarely has just one).
• Pre-money SAFEs (the older variant, where ownership was a share of pre-money).
• Interest, MFN (most-favored-nation), pro-rata rights, or side letters.
• Refresh option pools after the round.
• Different ownership at the cap vs. discount depending on the existing share count.

If your situation involves any of those, the number this calculator produces will be directionally useful but not authoritative. Y Combinator SAFE primer — yc

A Georgian-startup angle

If your Georgian LLC has taken SAFE money and you're now contemplating a Delaware flip, the SAFE doesn't automatically convert at the flip — it converts at the next priced equity round, which usually happens after the flip on the new Delaware entity. The flip itself can change the SAFE's denominators (new entity, new option pool) and your eventual dilution. Cooley GO — Delaware flips — cooley-go

Take this to your attorney

• Ask whether your SAFE is post-money or pre-money — the math is different.
• Ask about MFN and side letters with prior SAFE holders.
• Ask how the option pool will be sized at the priced round, and whether a refresh is contemplated.
• If you're flipping, ask whether the SAFE assigns cleanly to the new Delaware entity.