( Formula ) Begin with an equal sign

Two CDs purchased in February cost $12.99 and $16.99. The total of these two values is the CD expense for the month.

You do math in Excel by typing simple formulas into cells. Excel formulas always begin with an equal sign (=). Here's the formula typed into cell C6 to add 12.99 and 16.99:
=12.99+16.99
The plus sign (+) is a math operator that tells Excel to add the values.

1 Type the formula in cell C6.
2 Press ENTER to display the formula result.
3 Any time you select cell C6, the formula appears in the formula bar.

If you wonder later on how you got this result, the formula is visible in the formula bar near the top of the worksheet whenever you select cell C6 again.

Use other math operators

Math operators
Add (+) =10+5
Subtract (-) =10-5
Multiply (*) =10*5
Divide (/) =10/5

Excel uses familiar signs to build formulas.

To do more than add, you would use other math operators as you type formulas into worksheet cells.

You would start each formula with an equal sign and use a minus sign (-) to subtract, an asterisk (*) to multiply, and a forward slash (/) to divide.

Note You could use more than one math operator in a single formula. This course covers only single-operator formulas, but you should know that if there's more than one operator, formulas are not just calculated from left to right.

Select cell B7 and then click the AutoSum button.
A color marquee surrounds the cells in the formula, and the formula appears in cell B7.
Press ENTER to display the result in cell B7.
Select cell B7 to display the formula in the formula bar.

Total all the values in a column

To add up the total of expenses for January, you wouldn't have to type all those values again. Instead you could use a prewritten formula, called a function.

You could get the January total by selecting cell B7, then clicking AutoSum on the Standard toolbar. This enters the SUM function, which adds up all the values in a range of cells. To save time, use the function whenever you have more than a few values to add up, so that you don't have to type the formula.

Pressing ENTER displays the SUM function result 95.94 in cell B7. The formula =SUM(B3:B6) appears in the formula bar whenever cell B7 is selected.

B3:B6 is the information, called the argument, that tells the SUM function what to add. By using a cell reference (B3:B6) instead of the values in those cells, Excel can automatically update results if values change later on. The colon (:) in B3:B6 indicates a cell range in column B, rows 3 through 6. The parentheses are required to separate the argument from the function.

The next two sections explain cell references and functions in more detail.

Copy a formula instead of creating a new one

Drag the black cross from the cell containing the formula to the cell where the formula will be copied, then release the fill handle.
Auto Fill Options button appears but requires no actions.

Sometimes it's easier to copy formulas than to create new ones. In this example, you'll see how to copy the January formula and use it to add up the February expenses.

You would select cell B7, which contains the January formula, then position the mouse pointer over the lower-right corner of the cell until the black cross (+) appears. Next, drag the fill handle over cell C7. When the fill handle is released, the February total 126.93 appears in cell C7. The formula =SUM(C3:C6) is visible in the formula bar near the top of the worksheet whenever cell C7 is selected.

After the formula is copied, the Auto Fill Options button appears to give you some formatting options. In this case you wouldn't need to do anything with the button options. The button disappears when you next make an entry in any cell.

Note You can drag the fill handle to copy formulas only into cells that are next to each other, either horizontally or vertically.