LibreOffice Calc: Calculating sums, averages, and creating financial records

August 28, 2026

Welcome back to our tutorials on LibreOffice Calc. In the last LibreOffice Calc tutorial, we got a basic grasp of some on the program, how to access it, and how to use it effectively. Today, we'll be showing how to perform some basic calculations and introduce you to a special currency button to assist you in creating financial spreadsheets. I've created a simple spreadsheet pictured below to start.

Here you can see we have 6 products listed on the left-hand side of the spreadsheet and the amount of sales of each product on each day of the week in the middle. We'll be asking LibreOffice Calc to calculate the totals and averages of each column of data and printing it below each column.

The sum selection box.

I added the text 'Total' and 'Average' below the products listed on the left. We can start calculating the total or sum as it is called by typing out "=SUM" and then pressing the 'Enter' key. When we do this, LibreOffice Calc will automatically add a set of parenthesis next to the word SUM in the box we are calculating this in and the program will allow us to select a range of cells by clicking and dragging with our mouse to calculate the total of. Here, I have selected cells B4 to B9 and I am printing the result in cell B11. When I press enter, the total will be automatically calculated for cells B4 to B9. I've gone ahead and done the same to each of the other columns pictured below.

The average selection box.

Now we'll calculate some averages. Similar to calculating the sum, we have to choose a cell to calculate the average in. Here, I chose cell B12 and I type out "=AVERAGE" and then press enter, which will automatically add a set of parenthesis next to the word AVERAGE. Like calculating the total in the previous step, I will select cells B4 to B9 and hit enter. LibreOffice Calc will know how many values are selected based off of your selection every time, but if you would like to calculate the averages automatically, you can instead write in your average column "=B11/6" (the total of columns B4 to B9 divided by 6, which is the number of products). I much prefer calculating the averages with the =AVERAGE command because it can make it easier to scale your data as you get more data points over time.

Selecting the row of averages to reduce the amount of decimal places.

As you can see in the image above, we have our totals and averages calculated out now, but some of the averages have too many decimal places and will need to be cleaned up. This can be easily done by selecting the row of averages and formatting the row as a number.

The Format as Number button.

The Format as Number button is located on the third toolbar from the top as pictured above. Clicking this button while your column (or in this case, row) is selected will automatically format your data to have only two decimal places. Any non-repeating decimal number will be rounded up automatically and this will just make your data look even cleaner. Now, we'll take a look at another data set, but apply what we learned to prices.

Our cleaned up averages row after using the Format as Number button.

Averaging and totaling prices and adding currency identifiers

Here's another spreadsheet I created for those same products, but for their prices.

We're going to transform this column of prices so that it accurately translates to others that these are monetary values. We can do that by selecting our column in question and clicking on the 'Format as Currency' button on the same toolbar where we found the Format as Number button.

Formatting the column to show the dollar amount.

When we click on the Format as Currency button, we'll have a drop down menu appear that allows us too select what ever currency we want to display. Here, I'll be choosing '$ Default' at the top to represent U.S. dollars.

Our product prices in dollars with their totals and averages also in dollars.

I've preemptively also calculated the total and average using the methods we outlined earlier and also formatted those values in USD using the Format as Currency button. In this instance, I didn't have to format any of these values as numbers with the Format as Numbers button because they only contained two decimal points. If we didn't format the prices as a currency before, we might have had more than two decimal points in our results, but LibreOffice Calc is smart because it knows USD can only have two decimal points in it. Anyway, that's all for this tutorial. Hopefully, you're starting to see the practical applications of this program by now. In the next LibreOffice Calc tutorial, we will be discussing how to calculate medians and modes. As always, if there is anything you feel I haven't touched on, please let us know here at BootDrive by sending us a message through our Contact form on our homepage. Thanks for reading and I hope this helped!