For probabilities, use Fermi numbers, not words

Founder takeaway

Replace verbal probability labels such as “unlikely” with rough numerical estimates. Numbers make uncertainty explicit and reveal when teammates are using the same words to mean different things.

Why it matters

Ambiguous language can hide disagreement and create false alignment. Explicit estimates give founders a clearer basis for comparing risks, testing assumptions, and deciding where to commit scarce resources.

Relevant guides

Put it to work

For your next uncertain decision, ask: “What probability would each of us assign, what assumptions drive it, and at what probability would our decision change?”