Formulas are the key to getting things done in Excel. By entering formulas, you can have Excel do the work for you. Formulas can perform calculations, return information, manipulate the contents of other cells, test conditions, and more. You can even use formulas to create entire charts and graphs!
To enter a formula, simply type an equal sign (=) followed by the formula you want to use. For example, to add up the values in cells A1 through A5, you would type the following formula:
Once you've typed in a formula, you can press Enter or Return to have Excel calculate the result. You can also use the mouse to click on another cell after typing the equal sign; this will automatically enter the cell reference for you.
If you need to edit a formula, simply click on the cell containing the formula and make your changes. Remember to press Enter or Return when you're done so that Excel will recalculate the result.