Half-Life Calculator
Find how much remains after a given time.
Runs in your browser. Nothing is uploaded — your input is processed on this device and discarded when you close the tab.
Half-Life Calculator
How to use this tool
- Enter the initial quantity, the elapsed time and the half-life in the same time unit.
- Press Generate to see the remaining quantity.
- Use Load sample for 100 after 30 time units with a half-life of 10.
Worked example
From 100 after 30 time units with a half-life of 10, three half-lives pass, so 100 x (1/2)^3 = 12.50 remains.
What this tool does not do / Limits
This assumes a constant half-life and simple exponential decay. Real decay chains, measurement error and changing conditions can make actual results differ.
Frequently asked questions
What does one half-life mean?
The time for half of the quantity to decay; after two half-lives a quarter remains, after three an eighth.
Must the time units match?
Yes. Elapsed time and half-life must use the same unit, for example both in years or both in days.
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