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Find the amount remaining, initial amount, time elapsed, or half-life for radioactive decay, and convert half-life to the decay constant.
Also covers: Radioactive decay calculator ยท Carbon dating calculator ยท Decay constant calculator ยท Exponential decay half-life
N = Nโ ร (ยฝ)^(t / Tยฝ)
N and Nโ can be in any unit (grams, atoms, counts per minute, %) as long as both use the same one. The defaults are carbon-14 (half-life 5,730 years) after 10,000 years.
Amount remaining (N)
29.829244
Working
Choose radioactive decay or the decay constant and which quantity to solve for; the form asks only for the others.
Each input has its own unit picker, so you can mix atm, kPa, L, mL, ยฐC, or years without converting first.
You get the result in your chosen unit and every other unit, plus the rearranged equation with your numbers in SI units.
N = Nโ ร (ยฝ)^(t / Tยฝ): after each half-life, half of what's left remains. After 3 half-lives, 1/8 (12.5%) of the original amount is left.
Carbon-14 has a half-life of about 5,730 years. Measure what fraction of the original C-14 is left, and solve for t: t = 5,730 ร logโ(Nโ / N).
ฮป = ln 2 / Tยฝ, the fraction of nuclei decaying per unit time. It's shown per second here; the mean lifetime is 1/ฮป.
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