OpenOffice Calc's builtin AVERAGE function makes calculating the average of a column easy.
Calc is the spreadsheet component of Apache's free Open Office suite of programs.
How an Average Is Calculated
An average is calculated by adding a group of numbers and dividing the total by the count of those numbers.
The example here calculates the average for the values in column C, which comes out to 13.5. If you were calculate this manually, you'd add all the numbers, and divide the sum by 6 (11 + 12 + 13+ 14 + 15 + 16 = 81; 81 ÷ 6 = 13.5). Instead of finding this average manually, however, you can tell OpenOffice Calc to do it for you using the AVERAGE function:
=AVERAGE(C1:C6)
Should any of the values in the column change, the average update appropriately.
The AVERAGE Function's Syntax and Arguments
In OpenOffice and other spreadsheet programs such as Excel and Google Sheets, a function's syntax refers to the layout of the function and includes the function's name, brackets, and arguments. The syntax for the AVERAGE function is:
=AVERAGE (number 1; number 2; ...number30)
Up to 30 numbers can be averaged by the function.
A function's arguments are the numbers affected by the function:
 Argument number 1 (required)—the data to be averaged by the function
 Argument number 2; ... number30 (optional)—additional data that can be added to the average calculations.
The arguments can contain:
 a list of numbers to be averaged
 cell references to the location of the data in the worksheet
 a range of cell references
If the data you want to average is spread out in individual cells in the worksheet rather than in a single column or row, enter each cell reference into the dialog box on a separate argument line (for example, C5, E4, G2).
Example: Find the Average Value of a Column of Numbers

Enter the following data into cells C1 to C6: 11, 12, 13, 14, 15, 16.

Select cell C7, where the results will be displayed.

Select Insert > Function from the menu along the top of the screen.

Choose Statistical from the Category list.

Select Average, and click or tap Next.

Highlight cells C1 to C6 in the spreadsheet to enter this range into the dialog box in the number 1 argument line; Click OK to complete the function and close the dialog box.
If you can't see the cells you need to click, drag the dialog box out of the way.
The number 13.5 should appear in cell C7, which is the average for the numbers you entered in cells C1 to C6. When you select cell C7, the complete function =AVERAGE (C1:C6) appears in the input line above the worksheet