Why Pie Graphs Should Only Be Used For Cake

A pie graph is one of the first graphs we learn as children. We are able to understand them, because we understand cake, and the inequality of your sister getting a bigger piece. It evokes emotion in us and helps us learn the concept of fractions.

Then we learn some basic Excel and find the graph button. Pie graph! I know that one! You click it and it instantly creates a beautiful, colourful graph.

A pie graph is rarely, if at all, the most appropriate graph to use.

In a pie graph, you’re always trying to compare two factors against each other. The area of each piece and then the angle of each piece. The human eye is not great at comparing either of these, and a pie graph stacks them.

In the graph below, we can understand that the orange section is the biggest… but by how much?

(note, this is all dummy data, and you can take a guess as to where I wrote this article!)

Well, clearly, we can just overcome that by putting the percentages on as labels.

Hmm. Now we have to keep flicking our eyes back and forward between the colours and the legend over on the side.

Let’s keep in mind that the purpose of data visualisation is to make things quicker to read, and going back and forward slows us down. So, let’s put our labels on so we don’t have to flick back and forwards.

Excellent. Now we have just created a messy version of this:

Aaaand we’re back where we started. So what’s a better way to visually represent this data?

A simple bar graph. No, it’s not quite as pretty, but we need to constantly ask ourselves – what is the point of data visualisation. To create something pretty, or to make data easier to understand? (I’m hoping you answered that it’s the latter)

In this example, we can clearly see and compare the relationship between each category and the rank of each type.

I know, it’s not as pretty, and perhaps not as immediately impressive, but it’s easier to understand and achieves its purpose much quicker and easier, and that, I would argue, is much more important than prettiness.

So when is a pie graph really useful? Well, here’s an example:

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At Presentation Boss, we are all about the art of communication. We help people speak up in meetings, promote their ideas and present themselves professionally.

Kate Norris started her speaking career as a data analyst, unknowingly torturing her audiences with poor speaking skills and awful PowerPoint presentations, and soon became aware something had to change. Thus began her quest to find how to present dry, serious material (like numbers and data) in a way that makes people listen and understand. Years of speaking, stand-up comedy and presentation training later, she now helps people clearly identify their message and present engaging presentations... without pie graphs.