wikiHow Half-Life Calculator The half-life of a substance or a process refers to the time it takes for half of the quantity or activity to decay or change. The calculation of half-life depends on the specific substance or phenomenon you are dealing with. For radioactive decay, which is a commonly known example, the half-life is the time it takes for half of the radioactive atoms in a sample to decay. The calculation is based on the decay constant (λ) of the substance, which is a measure of how quickly the substance decays. The formula to calculate half-life (t1/2) in the case of radioactive decay is: t1/2 = (ln 2) / λ Where: t1/2 represents the half-life ln 2 is the natural logarithm of 2, approximately equal to 0.693147 λ is the decay constant of the substance, which depends on the specific radioactive isotope involved. To calculate the half-life, you need to know the decay constant, which can be determined through experimental measurements or obtained from reliable sources such as scientific literature or databases. It's important to note that half-life calculations can vary depending on the specific context or phenomenon you are dealing with. Page