Half-Life Decay Calculator
Exponential decay from half-life and elapsed time.
Inputs
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Formula
N = N₀ × (½)^(t/t½)
Remaining amount halves each half-life. Applies to radioisotopes, drug elimination, and first-order kinetics.
Worked example
After two half-lives (11460 years for ¹⁴C), 100 units decay to 25 remaining.
Where this can give the wrong answer
- Elapsed time cannot be negative.
- Assumes constant half-life — environmental factors can shift effective t½.
- Zero half-life is rejected.
FAQ
- λ = ln(2)/t½. The calculator reports λ from your half-life.