Half-Life Calculator — t½ = ln2/k

For any first-order process — radioactive decay, many decompositions — the half-life depends only on the rate constant, never on how much you start with. Convert either way between k and t½.

Half-Life Calculator — t½ = ln2/k

$t_{1/2} = \frac{\ln 2}{k}$

Solve for

First-order rate constant (k)

Unit

Result unit

How to interpret the result

Worked check: carbon-14 with k = 1.21×10⁻⁴ yr⁻¹ → t½ = 0.6931 / 1.21×10⁻⁴ = 5728 years, the basis of radiocarbon dating. Keep k and t½ in matching time units.

Assumptions

First-order kinetics (this relation fails for other orders)
k and half-life use the same time unit