Half-Life Calculator
How much of a substance remains after a given time of decay.
Result
Amount remaining
12.5000
Percent remaining (%)
12.50
How it works
Remaining = initial × (1/2)^(time ÷ half-life)
Each half-life halves the amount left. After three half-lives, only one eighth (12.5%) remains. Use the same time unit for half-life and elapsed time.
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Frequently asked questions
What is a half-life?
The time for half of a substance to decay — constant regardless of how much you start with.
How much is left after 3 half-lives?
One eighth, or 12.5%, of the original amount.
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