Under the right circumstances, pie charts are great for showing part-to-whole relationships; however, our perceptual system is bad at comparing areas or angles accurately. If you use a pie chart, a best practice is to use a dimension with two to five categories, and add labels to help your audience make more accurate judgments.
Pie charts are useful for:
- Showing a high-level breakdown of a measure by dimension with two to five categories
- Filtering or highlighting actions on a dashboard