What is a cumulative sum in Excel?

A cumulative sum is a total amount resulting from the addition of several values. In Microsoft Excel specifically, it is a value reached by adding the numbers in a group of columns or rows.

In order to use the cumulative sum function in Excel, first choose the cells to be included. If, for example, the desired sum is of the numbers in cells A1 through A5, highlight a blank cell and enter the formula =SUM(A1:A5). By using the sum function in this way, any subsequent changes made in the included cells also changes the sum to reflect the new total.