Enter an initial amount, its half-life, and an elapsed time (in the same units) to calculate how much remains after exponential decay.
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Half-life describes the time it takes for a quantity to reduce to half its value through exponential decay. This calculator applies the formula: remaining amount = initial amount × 0.5^(elapsed time ÷ half-life), directly modeling how the substance halves repeatedly over each full half-life period.
Half-life is most commonly associated with radioactive decay (like carbon-14 dating, half-life about 5,730 years), but the same math applies to drug elimination from the body, and any other process that decays at a rate proportional to its current amount.
Yes, both values must use the same time unit (both in years, both in hours, and so on) for the calculation to be correct.
The formula works for any elapsed time, the remaining amount just keeps approaching (but never quite reaching) zero.
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