Data Visualisation - Why Pie Charts Suck!

Pie charts are commonly used to visualise data, but they often leave a lot to be desired. There are much better options available to share data with your audience.

Why Do We Visualise Data and What is a Pie Chart?

Data analysis can uncover some important insights, and one of the best ways to communicate these is using effective data visualisation. Bar graphs, line graphs, pie charts, and histograms are just some of the various ways to visualise data. Picking the right visualisation tool is essential in getting your message across and keeping your readers or listeners engaged.

So, what is a pie chart? A pie chart is a circular graph in which the proportion of each segment is represented by its relative size.

 Simple example pie charts

Source: Exceljet

Why use pie charts? Pie charts are highly visual, simple to create, and often easy to understand. They allow viewers to make a visual comparison of the different sizes of the segments immediately.

What's Wrong With Pie Charts?

If you are like most people, you were introduced to pie charts early in life. Used with the right types of data, they can be effective in giving your audience an immediate understanding of the data without going into too much depth.  

Despite their benefits, the drawbacks of pie charts are significant and therefore worth exploring. So, why avoid using pie charts?

Comparing Segments Can Be Challenging

One of the perks of a pie chart is that it is easy to quickly identify the relative proportions of the segments. When these slices get closer in size or are not next to each other, it can, however, become difficult to visually estimate the relative proportions.  In the pie chart below for example, it is almost impossible to identify the clear proportions of each slice without having additional information (like percentages). 

pie chart no label
Source: PlotDigitizer

Percentage or absolute value labels are often added to the segments to make it easier to compare all the segment sizes when it is challenging to do so by eye.

While you might be tempted to chart your data with a labelled pie chart, you’re better off presenting the numerical values in a table or another visualisation.

Pie Charts Don’t Work as Well When Comparing Absolute Numbers

One of the key design elements of a pie chart is that each segment represents a percentage of the whole. You might want to label your visualisation with absolute numbers instead. Pie charts fall short when you want to compare segments in more than one pie chart to identify trends.

Pie Charts Are Not Good at Showing Trends

Pie charts work best when there is one set of data. When you start looking at budget spend data for different years, for example, you are going to need multiple pie charts to show each year. Not only will this take up a lot of space, it is not the most effective way to show how amounts in the same category have increased or decreased over time.

 pie chart comparisonSource: IELTS Liz

Not all of the disadvantages of pie charts can be put on the chart itself. Sometimes the user isn’t aware of which situations you need to steer clear of a pie chart.

Pie Charts Don’t Work When the Percentages Don’t Make 100

If you attempt to use a pie chart to represent data where the percentages don’t add up to 100, you end up with a misleading visualisation. If you represent values that do not make up the proportion of a whole, your audience is likely to be confused (see example below).pie chart not 100
Source: O’Reilly

Pie Charts Don’t Work Well With Too Many Segments

If you have a pie chart with more than 20 or even more than 10 slices, it can start to look cluttered. Visualisations should be clear and simple, but with that many categories, a pie chart can soon lose its meaning and fail to represent the data well.

pie chart manySource: BusinessInsider

What’s Better Than a Pie Chart?

The good news is that there are several great alternatives to pie charts. Here are some examples:

Bar chart

You don’t have to look too far for better ways to visualise data. The tried and tested bar chart (vertical or even horizontal) makes it much easier to compare the relative values of different segments side by side.

bar chartSource: Chartio 

Line chart

This is an effective tool for visualising multiple data sets and showing trends over a period of time. With a line chart, you can clearly visualise trends within a single visualisation, which is much easier to understand than having separate pie charts for different time periods.

Picture1Source: Fusion Charts

Conclusion: Why You Should Never Use A Pie Chart Ever Again

It’s apparent that pie charts do not do justice to your sales and marketing presentations. They are often simplistic, misleading, or incapable of clearly portraying more complex trends. 

Every business scenario is unique, and the data you have to share deserves a more robust tool than a pie chart. With so many data visualisation tools at your disposal, perhaps it is time to bid your last farewell to the pie chart.