A formula may also include a function, or predefined computational task, such as the AVERAGE or SUM function. Functions are useful when you want to perform calculations without having to type the formula (e.g., =(B3+C3+2D3)/4) in the formula bar.

Basically, functions are built-in features that perform specialized calculations on a selected set of data and offers the end-results of that calculation. Really, they replace the more complex mathematical formulas as well as performing logical calculations and text manipulation to retrieve information about the Excel worksheet.

The SUM function is one of the most common functions in spreadsheets. SUM is so common that it has its own button on the Standard Toolbar. However, you can access many others through the Paste Function utility that will be discussed later in the tutorial.

The general structure of functions goes like this:

The worksheet below illustrates the AVERAGE and SUM functions of our classroom database. As you can see, the functions help us from having to input the entire calculation (=B3+C3+D3 and =B3+B4+B5+B6+B7/5) into the formula bar.

 There many more types of functions that can be used. Click on the following buttons to go to that specific function.