Half-Life Calculator

Remaining quantity after radioactive or exponential half-life decay.

Half-Life Calculator helps you remaining quantity after radioactive or exponential half-life decay. Enter initial quantity, half-life, and elapsed time, review the breakdown, and use the guidance below to understand what the number means — and what it does not. What the Half-Life calculator does Half-Life Calculator is built for arithmetic, algebra, geometry, and number tools. Remaining quantity after radioactive or exponential half-life decay. You enter initial quantity, half-life, and elapsed time, then Simple Calculators computes the result instantly. Results use standard school and engineering formulas that run privately in your browser. How the math works Enter the Initial quantity, pick a Time unit, then enter the Half-life and the Elapsed time in that unit. The calculator counts how many half-lives have passed (elapsed time ÷ half-life) and halves the starting amount that many times: amount left = initial × (1/2)^(time ÷ half-life). The answer is in the same unit as your starting amount, and a table shows the amount after each whole half-life. The formula: N = N₀ × (1/2)^(t ÷ t½). N₀ is the starting amount, t the time passed, t½ the half-life (same time unit as t), and N the…