Calculating the average age of a group tells you what age most of the people fall closest to. This statistic has applications for several different fields. For example, you could calculate the average age of a team to see if members are young or old, or you could calculate the average age of a class to see how old most students in a class are. Average is also known as the mean.

Add together all the ages in the group. For example, suppose a baseball team has nine players. There ages are 14, 17, 15, 19, 14, 16, 16, 17 and 15. The sum of their ages is 143.

Determine the total number of people in the group. In the example, the total number of teammates is nine.

Divide the total number of ages by the number of people in the group. In the example, 143 divided by nine equals 15.8889. So the average age of the baseball team is 15.889 years old.