Pie charts are an efficient and easy to read way to represent data in percentages or portions. However, it is sometimes difficult to include absolute numbers on a pie chart instead of percentages, particularly if there are many categories shown in the chart.
Pie charts are built in to many mathematical and statistical software packages, including Microsoft Excel, Minitab, SPSS and R. They are generally simple to create and do not require a lot of explanation when used in a report or a presentation.
While the reader of a pie chart can clearly see which categories dominate, it can be difficult to see categories that occupy only a small percentage of the chart. This problem becomes worse if there are many small categories in the chart. Labeling the categories can also be difficult, leading to either excessively long legends or multiple labels on the chart itself. Both of these options detract from the visual appeal and make it difficult to extract useful conclusions.
Pie charts are recommended for data sets with relatively few (five to 10) categories. To represent data in more than 10 categories, a bar chart of percentages with category labels on the horizontal axis is easier to read and interpret.