Why two small SAFEs cost you more than one big one

The most expensive misunderstanding at seed: founders treat each SAFE as a small, separate slice and assume they roughly overlap. With post-money SAFEs they don't overlap at all — their percentages add, and every added point comes out of the founders and the option pool, never out of another SAFE. Here's the arithmetic that makes "a few small SAFEs" turn into double-digit dilution.

The additive property

A post-money SAFE fixes ownership at principal ÷ post-money cap, measured on the post-money cap table. Because each SAFE's percentage is defined against that same post-money base, they don't dilute each other — they stack. Two SAFEs that are each 5% of post-money are 10% combined, not ~5%. There is no netting.

Worked example

• Founders: 9,000,000 shares.
• SAFE A: $600,000 at an $8,000,000 cap.
• SAFE B: $400,000 at an $8,000,000 cap.
• Priced round: $5,000,000 of new money at a $20,000,000 pre-money, 10% post-round option pool.

The two SAFEs claim 12.5% of the post-money cap table between them. After the round's new money and the pool dilute everyone, here's where it lands:

Why "one big SAFE" would be cheaper

If instead of two SAFEs you'd raised the same $1,000,000 in a single SAFE at a $16,000,000 cap (double the cap because you're raising in one bite at a stronger valuation), the block would be 1,000,000 ÷ 16,000,000 = 6.25% of post-money — half the 12.5% the two tight $8M-cap SAFEs produced. Same cash in the door, roughly half the dilution. The cost wasn't the dollars; it was signing two tight caps instead of negotiating one.

What this means when you raise

• Add your caps up before you sign the next one. Your total post-money SAFE ownership is the sum of every principal ÷ cap — track that running total, not each SAFE in isolation.
• Watch the "convenient" bridge SAFE. A quick $250k at a low cap to extend runway can add 3–5 points on its own, on top of everything already stacked.
• Model it before the term-sheet call. A lead computes your combined converted block first and reprices the pre-money against it. If you don't know the number, they set the anchor.