Drake Equation Calculator

How it works

N = R* × fₚ × nₑ × fₗ × fᵢ × f꜀ × L

Frank Drake wrote the equation in 1961 not as a prediction but as an agenda: it factors the question "how many civilisations could we detect?" into a chain of probabilities, each of which a different science can try to measure. The first three terms are astronomy and are now reasonably constrained by star counts and exoplanet surveys; the next three are biology, evolution and sociology, where we have a single data point; the last, L, asks how long a technological species keeps broadcasting, and it multiplies everything else. The product is therefore only as good as its weakest guess, which is precisely the point — the equation shows which unknowns matter most and turns vague optimism or pessimism into explicit numbers that can be argued about.

Worked example

With R* = 1.5 stars per year, every star having planets, 0.2 habitable planets per system, life on half of them, intelligence on 10% of those, technology on 20% of those and a detectable lifetime of 10,000 years, N = 1.5 × 1 × 0.2 × 0.5 × 0.1 × 0.2 × 10,000 = 30 civilisations, born about once every 333 years and spaced roughly 6,400 light-years apart.

Frequently asked questions