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Half-Life Calculator
Exponential decay: remaining quantity after time t.
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Results
Remaining
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Percent Remaining
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Half-Lives Elapsed
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How to use the Half-Life Calculator
N = N₀ × (1/2)^(t / half-life). Works for isotopes, drugs, and anything decaying exponentially.
Frequently Asked Questions
About 0.1% remains — for most purposes, gone. That's why '10 half-lives' is the rule of thumb for clearance.