# How do you calculate half life?

To calculate half of a life, you will first need to know how long the whole life is. If a person lived to be 80, then half of that life would be 40. You will just divide the age at which the person or animal died, by two.
Q&A Related to "How do you calculate half life?"
 1. Divide the amount of the substance at one point in time by the amount remaining after a period of time. The formula for calculating half life is as follows: t. 1/2. = t * ln(2) http://www.wikihow.com/Calculate-Half-Life
 1. Suppose you know the proportions of a substance at two points in time. Denote the difference between these two points in time with the letter "T. Denote the ratio of the smaller http://www.ehow.com/how_5946189_calculate-half_lif...
 Check the time between your first decay rate and when the decay rate reaches half this number. http://wiki.answers.com/Q/How_do_you_calculate_hal...
 Relative decay rate k = - ln2/5272. The amount of Cobalt-60 left after t years given by A(t) = A0e^kt) This implies A(1600) = 100e^ln2*1600/5272) = 81.0290 g. http://answers.yahoo.com/question/index?qid=200810...