Double-click on SUM to add the function to the field.

Click with the mouse button on the field below or to the right of the column or row with the numbers that you want to calculate the sum for.

If SUM is not displayed as a function, select Mathematical from the list and scroll down until you see SUM listed. Calc displays functions in a sidebar that it attaches to the right of the spreadsheet. You need to use a function if you want the sum to be calculated automatically by the program.

You can highlight the numbers to get the sum and the average displayed to you in the status bar of the program this may be sufficient for some tasks, but automation may speed things up further, especially if you use a function in templates as it will then be available automatically when you use that template. One of the most common things that Calc users do is calculate the sum of numbers, e.g. You enter data in a spreadsheet and may use advanced features such as functions or charts manually or automatically. Using Calc works pretty much the same as in Microsoft Excel.

Libreoffice calc