Creating Simple Formulas
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.
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.