Free · Physics models
Drake Equation Scenario Model
Explore how chosen star-formation, life and communication assumptions change a civilization-count scenario.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Number = 5.0000000. The worked example lists its inputs and unit conventions.
N = R* fp ne fl fi fc L.
Worked example
Enter these known values and leave the other values blank.
- Rate
- 1 stars per year
- Fraction
- 50 %
- Number of planets
- 2 planets per system
- Fraction
- 50 %
- Fraction
- 10 %
- Fraction
- 10 %
- 1000 yrs
- Number
- 5 civilizations
Assumptions and limitations
- This is a scenario product, not an empirical probability forecast or an estimate with quantified uncertainty. Enter hypothetical fractions between zero and one, effective suitable planets per system, positive star-formation rate per year and positive detectable lifetime in years. A zero fraction gives a zero count. Fractional output is an expected scenario count, not a census.
- Clear the unknown quantity to solve a supported inverse. Keep known quantities fixed with locks. A zero multiplier can make an inverse underdetermined.
Common questions
What assumptions apply?
This is a scenario product, not an empirical probability forecast or an estimate with quantified uncertainty. Enter hypothetical fractions between zero and one, effective suitable planets per system, positive star-formation rate per year and positive detectable lifetime in years. A zero fraction gives a zero count. Fractional output is an expected scenario count, not a census.
How do inverse controls work?
Clear the unknown and enter enough independent known values. Locks retain known quantities; singular or impossible inverses may remain incomplete.
References
Zero fractions produce a mathematically valid zero count; retain nonnegative scenario counts without treating a zero as an observed absence.