Half-Life Calculator
Find amount remaining, time elapsed or half-life for radioactive decay and other first-order processes. The result updates as you type, with the working underneath so you can check it.
Your details
Result
Amount remaining
25
- Half-lives elapsed
- 2
- Fraction left
- 25.00%
Good to know: N = N₀ × (½)^(t ÷ t½)
Please note: For study and planning. Check calculations independently before using results with chemicals, electricity, pressure or machinery, and follow safety data sheets, manufacturer instructions and local regulations.
About this tool
Formula
N = N₀ × (½)^(t ÷ t½)
Questions people ask
What is half-life?
The time for a quantity to fall to half its value. After two half-lives a quarter remains, after three an eighth.
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How we calculate this
We use the standard published formula or definition for this calculation, and we show the working so you can check it.
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