Alternatively referred to as the arithmetic mean, an average is the sum of a series of numbers, divided by the total amount of numbers. For example, suppose we have the following series of numbers: 1, 2, 3, 4, 1, 2, and 3. The sum of these numbers is 16, 16 divided by 7 is 2.28. Therefore, 2.28 is the average of these numbers.
In Microsoft Excel and other spreadsheets, you can determine the average of multiple cells with the appropriate formula. The formula in the example below determines the average of the values in cells A1 through F1.
With a spreadsheet with multiple averages, you can get the average of all averages with the same formula on the cells containing the averages. For example, if you had 20 averages in the D column, you could use the formula =AVERAGE(D1:D20) in the D21 cell.