Half-Life Calculator

Select what you want to calculate: remaining amount, elapsed time, half-life, or initial amount. Enter the known values including the initial quantity, half-life of the substance, and time elapsed (or remaining amount).

The calculator applies the radioactive decay formula: N(t) = N₀ × (1/2)^(t/t₁/₂), where N₀ is initial amount, N(t) is remaining amount, t is elapsed time, and t₁/₂ is the half-life. Alternative forms using decay constant λ are also available.

Results show the calculated value with proper units. A decay curve graph shows how the amount decreases over multiple half-lives. The calculator also shows how many half-lives have elapsed and the percentage remaining.