Half-Life Calculator
Enter known values, click Calculate, and the remaining values update automatically.
Inputs
λ is shown in per sec.
T, t, and τ use the same selected time unit.
sec
sec
per sec
sec
After the first calculation, changing a value or the time unit recalculates automatically.
Step-by-step derivation
Enter your known values, then click Calculate.
References
- Remaining quantity: N(t) = N(0) × 0.5^(t / T)
- Exponential form: N(t) = N(0) × e^(−λt) = N(0) × e^(−t / τ)
- Relations: T = ln(2) / λ = τ × ln(2)
- Rearrangements: t = ln(N(0) / N(t)) / λ, λ = ln(2) / T, τ = 1 / λ