Half-Life Calculator

A half-life is the time for half of what remains to decay — after one half-life 50% survives, after two 25%, after three 12.5%. The formula N = N₀(½)^(t/T) applies to radioisotopes, drug concentrations, and even the caffeine in your bloodstream.

Each half-life halves what's left, so the amount approaches zero without reaching it — after ten half-lives about 0.1% remains, the practical 'gone' threshold in medicine and radiology. Carbon dating reads this clock backward: measure the fraction left, count the half-lives.