### Creating a simple addition formula

A simple formula in Excel contains one mathematical operation only: one number plus a second number equals a third number. Writing a simple formula is really no more difficult than that: 1+1. The only difference in Excel is that all formulas **must** begin with the **equals sign** (=). It is not enough to type **1+1** in Excel because what will appear in the cell is "1+1". You must begin the equation with an equals sign, or **=1+1**. This holds true for any formula—simple or complicated—that adds, subtracts, multiplies, or divides.

Let's add two numbers to create a third: 128+345=473. In Excel XP, this would be expressed by the formula **=128+345**, as shown below.

#### To create a simple formula that adds two numbers:

- Click the cell where the formula will be defined.
- Type the equals sign (=) to let Excel know a formula is being defined.
- Type the first number to be added (128, for example).
- Type the
**addition sign (+)** to let Excel know that an add operation is to be performed. - Type the second number to be added (345, for example).
- Press
**Enter** or click the **Enter button** on the formula bar to complete the formula.

Excel **will not always tell you** if your formula contains an error, so it's up to you to check all of your formulas. To learn how to do this, read the Double-Check Your Formulas lesson in our Excel Formulas tutorial.