Half-Life Calculator
Enter an initial amount, half-life, and elapsed time to see what remains — plus the decay constant and mean lifetime.
Amount remaining (g)
12.50
Detalhamento
- Remaining (% of start)
- 12.50
- Half-lives elapsed
- 3
- Decay constant λ (per unit)
- 0.14
- Mean lifetime (units)
- 7.21
Última atualização:
FAQ
What is the half-life formula?
N(t) = N₀ × (1/2)^(t/t½) — the remaining amount equals the initial amount times one-half raised to the number of elapsed half-lives. Equivalently N(t) = N₀·e^(−λt) with λ = ln 2 ÷ t½.
How many half-lives until something is gone?
Never exactly — decay is asymptotic. After 10 half-lives only about 0.1% remains, which is the practical threshold where quantities are treated as negligible for most purposes.
What is mean lifetime?
The average lifetime of a particle, equal to 1/λ or t½ ÷ ln 2 ≈ 1.44 × t½. It is the time at which the amount has fallen to 1/e ≈ 36.8% of the starting value.
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