Are we alone? Nobody knows, but the Drake equation organises our ignorance into factors – star formation, planets, life, intelligence and how long civilizations last. Different assumptions give answers from “nobody else” to millions.
How to use the Alien Civilization Calculator
- Scenario
- Star formation rate R* (per year)
- Fraction of stars with planets f_p
- Habitable planets per system n_e
- Fraction developing life f_l
- Fraction developing intelligence f_i
- Fraction that communicate f_c
- Lifetime of communication L (years)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose a scenario or select Custom and enter every factor. The distance assumes civilizations are spread evenly across the galactic disk.
Inputs explained
| Field | What to enter |
|---|---|
| Scenario | Choose one: Optimistic, Moderate, Pessimistic, Custom |
| Star formation rate R* (per year) | A number |
| Fraction of stars with planets f_p | A number |
| Habitable planets per system n_e | A number |
| Fraction developing life f_l | A number |
| Fraction developing intelligence f_i | A number |
| Fraction that communicate f_c | A number |
| Lifetime of communication L (years) | A number |
Example values
How the main result changes when Star formation rate R* changes and everything else stays at the example values above:
| Star formation rate R* (per year) | Number of civilizations N |
|---|---|
| 0.75 | 27 |
| 1.13 | 27 |
| 1.5 | 27 |
| 1.88 | 27 |
| 2.25 | 27 |
| 3 | 27 |
Formula
N = R*·f_p·n_e·f_l·f_i·f_c·L, typical spacing ≈ √(πR²/N) in a galactic disk of radius R ≈ 50,000 ly
Worked example
Inputs — Scenario: Moderate.
Results — Number of civilizations N = 27; Typical distance to the nearest = 17,055 ly; Interpretation = A few, very far apart.
Key terms
- Drake equation
- Product of factors estimating communicating civilizations.
Frequently asked questions
Is the Drake equation a prediction?
No – it is a framework; most factors are unknown.
Why are scenario results so different?
Each factor can vary by orders of magnitude.
What is the Fermi paradox?
If civilizations are common, why haven't we seen any?
Which factor is best known?
Star formation rate and the fraction of stars with planets.