Last week I overheard two people talking about how pie charts should never be used. One of them was showing to the other what I believe was the graph on their phone, and he stated: “There are four pie charts here and I can’t even relate them”.
From that point, I already knew: the person who created the visualization was yet another victim of the misuse of pie charts.
It’s not uncommon to see people trying to compare data using pie charts, which is one of the biggest mistakes to make since the viewer will have to work very hard to digest and translate them to useful data.
But then, when is the right moment?
When you want to show percentages or relative proportions of information.
That’s it, there’s only one application, and for this specific use pie charts are the best. For every other situation where you think a pie chart will be a good idea, the bars or stacked bars are surely a better option, trust me.
Anyhow, there are a couple of things you should consider before using your pie chart:
- Pie charts are better used if you have other graphs/visualizations supporting it.
- Limit your pie wedges to something between 4 and 6, more than that go for a bar chart.
Here’s an example on how pie charts should not be used. I’m trying to compare the sales revenue of every department in the first quarter.
This could even mislead the viewer by thinking they had a better Hardware sales in February if you compare to January (the pie wedge is bigger), which is not true.
Here’s an example where a pie chart supports the main report with a quickly and graphic view.
Hopefully the person who created the visualization from the talk I overheard last week will check this post.