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    Half-Life Calculator

    Calculate the remaining amount, half-life or elapsed time with this free online half-life calculator. Includes caffeine and carbon-14 presets and a decay table.

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    How to use Half-Life Calculator

    1. 1Choose whether to find the remaining amount, the half-life or the elapsed time
    2. 2Pick a preset such as caffeine or carbon-14, or enter your own half-life and time unit
    3. 3Enter the known values and read the result, the decay constant and the half-life table

    Frequently asked questions

    What is the half-life formula?▾

    The remaining amount is N = N0 × (1/2)^(t/T), where N0 is the initial amount, t the elapsed time and T the half-life.

    How much carbon-14 is left after 10,000 years?▾

    Carbon-14 has a half-life of 5,730 years, so after 10,000 years about 29.8% of the original amount remains.

    How long does caffeine stay in your body?▾

    Caffeine has a half-life of about 5 hours in healthy adults, so half of a 200 mg dose is still present after 5 hours and a quarter after 10 hours.

    Embed Half-Life Calculator on your website▾

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