AutoSum is a Microsoft Excel and other spreadsheet program function that adds together a range of cells and displays the total in the cell below the selected range. For example, if you wanted to add the values of cells between A1 and A5, highlight cells A1 through A5 and click the AutoSum button (shown right). Clicking this button after highlighting the cells creates the formula =SUM(A1:A5) in cell A6 (first cell after last highlighted cell) and gives you the total of all those cells.
The AutoSum feature makes entering formulas easy without the need to memorize the syntax for each one.
In Excel 2010 and later, the AutoSum feature is on the Home tab, in the Editing section.