Half-Life Calculator

Half-life is the time required for a quantity of a substance to reduce to half of its initial value. In physics, it describes how quickly unstable atoms undergo radioactive decay. In pharmacology, it refers to the time it takes for a biological system to eliminate half of a administered drug.

The core exponential decay equation is N(t) = N₀ × (1/2)^(t / t_half), where N(t) is the remaining quantity, N₀ is the initial quantity, t is the elapsed time, and t_half is the half-life of the substance.

Radioactive half-life is a constant physical property determined solely by the isotope's nuclear stability. Biological half-life depends on complex bodily processes like metabolism and excretion, which can vary between individuals depending on health, age, and genetics.

No. Radioactive decay is a spontaneous nuclear process. It is completely unaffected by physical or chemical changes, including temperature, pressure, chemical reactions, or magnetic fields.

For each elapsed half-life, divide the remaining amount by 2. After 1 half-life, 50% remains. After 2 half-lives, 25% remains. After 3 half-lives, 12.5% remains. Mathematically, the fraction remaining after 'n' half-lives is (1/2)^n.