How this calculation works
Infer a half-life from two observations under a constant exponential decay model.
THE FORMULA
Half-life = elapsed time × ln(2)/ln(start/end)A worked example
A drop from 80 to 20 over six units of time represents two half-lives of three each.
Good to know
Use a positive declining quantity with a constant decay rate.
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Read the result
Infer a half-life from two observations under a constant exponential decay model.
The primary result is labeled “Half-life”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
Use a positive declining quantity with a constant decay rate.
For a related exercise, try the quadratic equation solver.
A few questions, answered
How can I check the default inputs by hand?
A drop from 80 to 20 over six units of time represents two half-lives of three each.
Which rule does this calculator apply?
Half-life = elapsed time × ln(2)/ln(start/end)