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Half-Life Calculator
Work out how much of a radioactive sample remains after a given time, or how long a decay takes to reach a chosen level.
N = N₀ × (½)^(t ÷ T½)
After each half-life the undecayed amount halves, so the remaining quantity falls exponentially with time.
Remaining amount
… nuclei
The calculation runs entirely in your browser, no data leaves your device. Change any number and the answer updates instantly.