Drake Equation Calculator
The Drake equation — the number of civilisations in the galaxy we could detect, as a product of star formation, planets, habitability, life, intelligence, technology and longevity — with the running product and the factor that matters most.
Frank Drake wrote it in 1961 not to get an answer but to organise the question: multiply the rate of star formation by the fraction with planets, the habitable planets per system, and the fractions on which life, intelligence and detectable technology arise, then by how long such a civilisation stays detectable.
How the drake equation calculator works
Frank Drake wrote it in 1961 not to get an answer but to organise the question: multiply the rate of star formation by the fraction with planets, the habitable planets per system, and the fractions on which life, intelligence and detectable technology arise, then by how long such a civilisation stays detectable. The first three factors are now measured; the last four are guesses spanning many orders of magnitude.
The running product shows how many stars a year become anything at each stage, and longevity is almost always the term that dominates.
Formula: N = R* × f_p × n_e × f_l × f_i × f_c × L
Worked examples
| Inputs | Detectable civilisations now | Note |
|---|---|---|
| A middle-of-the-road guess | 3 | about 3 |
| Pessimistic on life | 0.03 | we are probably alone |
| Long-lived civilisations | 300 | hundreds |
FAQFrequently asked questions
What is the Drake equation?
A way of estimating how many civilisations in our galaxy could be detected by radio, as a product of seven factors. It was written to set the agenda for the first SETI meeting in 1961.
Which factors are known?
The star formation rate, about 1.5 to 3 a year; the fraction with planets, close to 1; and the habitable planets per system, roughly 0.1 to 0.4 from Kepler. The rest are unknown.
Why does L dominate?
Because the other factors set how often civilisations arise, and L sets how many overlap in time. A civilisation that broadcasts for a century is almost never on air at the same time as another.
What answer did Drake get?
His 1961 group settled on something between 1,000 and 100 million. Modern pessimists get well under one; the honest answer is that the equation spans that whole range.
Is it science?
It is a framework, not a theory — it cannot be tested and its unknowns are guesses. Its value is in showing exactly which unknowns matter.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G and the speed of light
- IAU 2015 Resolution B3 — nominal solar and planetary conversion constants — the astronomical unit, solar mass and planetary radii
- Royal Observatory Greenwich — the historic home of the prime meridian
Last checked: September 2026. Constants are CODATA 2018 (G, c) and IAU 2015 nominal values (solar and planetary parameters).