What are the units of a half-life?

1 Answer
Jul 13, 2016

The units of half-life are time.


The units of half-life are time. The half-life is the length of time that it takes for half of an initial sample to undergo a change. Usually this is the radio-active decay of a specific atomic weight of an element. For example, the half-life of Uranium-238 is 4.46 billion years.

The formula for half-life which gives the number of remaining atoms after a time, #t#, and starting with #N(0)# atoms in the sample:

#N(t) = N(0) (1/2)^(t/t_(1//2))#

where #t_(1//2)# is the half-life in units of time. This is clear from the formula, since the power must be unitless, so the units of half-life must cancel with the units of the time, #t#.