Pie charts are exclusively used in presentations, dashboards and reports. Yet they have a very bad reputation among data visualization designers. I believe this bad reputation is the result of using pie charts without consideration and in instances where another chart is a better option.
While data visualization designers are not fond of pies and donuts, the audience will always like a nice looking circle in the presentation. In my work I have been asked many times by clients to specifically include a pie chart.
There is a good reason audiences prefer them too. One of my favorite data visualization books, The big book of circles, describes many use cases of not only pie and donut charts but other circle graphs. Being a big space and astronomy lover I can argue that this fondness we have to circles is because the universe is largely comprised of circles: the Earth, the Moon, other planets, the Sun, other stars, etc. All these celestial bodies are perfect circles.
What is a pie chart?
Pie charts a circle graphic devided into slices that represnet the numerical value of the categories compared. Pie charts are great to show parts of a whole or in other words the share that each category contributes to a whole. In most cases pie charts are used to show percentage values and are best used when there are no more than thre categories. With more than three categories pie charts can become cluttered and hard to read.
With all that said, pie charts are here to stay and will always be appreciated by business stakeholders.
If you need to include a pie chart in your presentation or report here are my tips on how to design and create pie charts that would be easier to read and understand.
Pie Chart with Highlight
Using a highlight color to draw attention is a great data viz technique for any chart. It can be very useful for pie charts specifically to highlight a slice you want to focus on and the story is in the detail of how this specific category slice contributes to the whole. As an example below the pie chart is showing website visitors by marketing channel. It highlights Organic traffic to show its huge contribution to overall website visitor number.
Pie Charts with Gradient Colors
Gradients colors represent values in heatmaps so that audiences can easily see largest to smallest values. This can be a good approach for a pie chart if there is no specific categories that needs highlighting. Remember the data needs to be sorted by largest or by smallest values. In the example below we are looking at the same website visitor data to see largest to smallest value.
Pie Charts with Color Groups
This example is not ideal but it is an option to use a pie chart with multiple categories. Grouping them into a color category starting with largest or smallest would also make it easier for the audience to follow the data and understand it.
I believe pie charts serve a purpose. If used wisely and with correct data they can add a little infinite circle beauty to your dashboards, presentations and reports. Here is a concept pie chart visualization for more inspiration.