A pie chart is an effective visualization when showing the relationship of different parts to a whole, especially if the dataset contains a limited number of categories (typically 2-5 or up to 6). It is best used to emphasize how one category or slice is significantly larger or smaller than others, providing a quick visual sense of proportions and part-to-whole relationships. Pie charts are most helpful when the total sums to a meaningful whole (such as percentages adding up to 100%) and the goal is to make the part-to-whole comparison immediately clear and visually appealing. However, they should be avoided if the number of categories is large, the slices have similar sizes, or the data does not represent a uniform whole.
When to use a pie chart:
- To show parts of a whole where the total adds up to 100%.
- When there are few categories (ideally between 2 to 5-6).
- When one or two categories significantly outweigh others.
- When the goal is to communicate simple proportion differences clearly and quickly.
- When the data are percentages or can be expressed as such.
- When visual appeal and simplicity are important for easy understanding.
When to avoid pie charts:
- If there are many small categories or slices.
- When categories have similar values that are hard to distinguish by slice size.
- If exact comparison of values is important.
- When data do not sum to a meaningful whole.
- For complex datasets requiring detailed trend or group comparisons.
Best practices:
- Label each slice clearly with values or percentages.
- Order slices by size to aid comparison.
- Avoid 3D effects or excessive visual embellishments.
- Consider combining small slices into an "Other" category.
- Use distinct colors or patterns to differentiate slices for clarity.
Pie charts are familiarly shaped and intuitively understood as part-to-whole visualizations but should be chosen wisely to avoid misinterpretation and ensure effective communication of the data story.
