Dos and Don’ts of Data Visualisation

Pie charts: cons (and pros)

The human brain thinks linearly: we can easily compare lengths/heights of line segments but when it comes to angles and areas most of us can't judge them well. Therefore, try to avoid the use of pie charts when comparing many categories or when categories have similar values.

However, pie charts do work well to display a total and shares thereof, and they are readable if they display only a few categories (maximum 5-6). Other good practices are: to sort the values in a clockwise manner according to your communication aim; to have the labels close to the pie chart (avoid unnecessary effort from the reader); and to use the colours wisely or even use only one colour if the pie chart has labels (to eliminate redundancy). With a specific communication aim, a pie chart with many slices can be used to highlight the biggest or the smallest share.

If you want readers to compare the shares of a total, bar charts and stacked bar charts are better alternatives