To use the sum button, you select the cell below or to the right of the column or row of numbers you want to sum, and click on the AutoSum button
Illustration #1 Worksheet
You can enter multiple sum formulas in a worksheet, by selecting the range where you want the formulas and clicking on the AutoSum Button.
Illustration #2 Worksheet
Another technique is to select a range that includes the values you want to sum and the row where you want the formulas inserted, and then click on the AutoSum button.
Illustration #3 Worksheet
Totaling both the columns and row simultaneously is easy. Pre-select the entire range to include the data and the row and column cells where you want the formulas inserted.
Illustration #4 Worksheet
Need grand total when sub-totals exist? AutoSum can handle it for you. Subtotals must be inserted first, then pre-select the entire range including the data, sub-total rows, grand total rows, and total column. Excel ignores the values and adds the subtotals.
Division Subtotals Worksheet