Google Spreadsheets has several functions that make it easy to find some of the more commonly used average values. These include:
 The AVERAGE function — finds the arithmetic mean for a list of numbers.
 The MEDIAN function — finds the middle value in a list of numbers.
 The MODE function — finds the most commonly occurring value in a list of numbers.
Learn how the AVERAGE function works and how to use it in a Google spreadsheet.
The AVERAGE Function's Syntax and Arguments
A function's syntax refers to the layout of the function and includes the function's name, brackets, comma separators, and arguments.
The syntax for the AVERAGE function is:
=AVERAGE(number_1, number_2, ...number_30)
 number_1 — (required) the data to be averaged by the function
 number_2 to number_30 — (optional) additional data values to be included in the average. The maximum number of entries allowed is 30
The number arguments can contain:
 A list of numbers to be average.
 Cell references to the location of the data in the worksheet.
 A range of cell references.
 A named range.
Text entries and cells containing Boolean values (TRUE or FALSE) are ignored by the function.
If you alter cells that are blank or contain text or Boolean values later to hold numbers, the average will recalculate to accommodate the changes.
Blank Cells vs. Zero
When it comes to finding average values in Google Spreadsheets, there is a difference between blank or empty cells and those containing a zero value.
Blank cells are ignored by the AVERAGE function, which can be very handy since it makes finding the average for noncontiguous cells of data very easy. Cells containing a zero value, however, are included in the average.
Finding the AVERAGE Function
As with all other builtin functions in Google Spreadsheets, you can access the AVERAGE function by selecting Insert > Function in the menus to open a dropdown list of commonly used functions that includes the AVERAGE function.
Alternatively, because it is so widely used, a shortcut to the function has been added to the program's toolbar to make it even easier to find and use.
The icon on the toolbar for this and several other popular functions is the Greek letter Sigma (Σ).
Google Spreadsheets AVERAGE Function Example
The steps below cover how to use the shortcut to the AVERAGE function mentioned above.

Select the cell where the formula results will be displayed.

Select the Functions icon on the toolbar above the worksheet to open the dropdown list of functions.

Select Average from the list to place a blank copy of the function in the cell.

Select the cells you want to enter these references as arguments for the function and press the Enter key on the keyboard.

The average number should appear in the selected cell. When you select the cell, the complete function appears in the formula bar above the worksheet.
Individual cells, rather than a continuous range, can be added as arguments, but a comma must separate each cell reference.
After entering the function, if you make changes to the data in the selected cells, the function, by default, automatically recalculates to reflect the change.