Data Visualization with Pie Charts

Data visualization with pie charts

Pie charts are one of the simplest ways to show how a whole is divided into parts. A pie chart is a circular graph that uses slices to represent numerical proportions. Each slice’s size is proportional to the value it represents, and all slices together add up to 100 percent. Pie charts are ideal for visualizing part-to-whole data when you have a small number of clear categories.

What a Pie Chart Shows

Pie charts are useful for:

• Showing proportions and percentages.
• Highlighting how a dataset is divided into its main components.
• Displaying part-to-whole relationships where each slice represents a piece of the overall total.

How Pie Charts Work

A pie chart uses two required fields:

1. A category label.
2. A numeric value.

The charting tool calculates the percentage of each value automatically and converts those percentages into slice angles. Larger values create larger slices, smaller values create smaller slices, and all slices complete a full circle.

When should you use a pie chart?

Pie charts are best when you want to communicate a quick, high-level breakdown. They work well when:

• You have only a few categories, typically three to five.
• The values have clear differences in size.
• You want to show what portion each group contributes to the whole.

For example, if you want to understand how many employees have completed training, how many are in progress, and how many have not started, a pie chart provides an instant answer.

Pie charts are not ideal when many slices have similar sizes because people struggle to compare visual areas. They are also not useful when you need to compare categories across multiple groups or time periods. In those cases, a bar or line chart is more effective.

Best practices for pie charts

Follow these best practices to keep your pie charts clear and accurate:

• Use a maximum of five slices.
• Combine small categories into an “Other” group.
• Clearly label each slice with percentages or values.
• Start the largest slice at the top and rotate clockwise.
• Avoid comparing multiple pies side by side.
• Avoid 3D effects because they distort perception of size.
• Use contrasting colors so each slice is easy to distinguish.
  

Ways a pie chart can support your BI

Pie charts can help leaders answer quick, part-to-whole business questions across departments.

Track top performers

Show which store, region, or product contributes the most revenue.

Visualize growth contributors

Identify which products or business units are driving profit increases.

Understand customer types

See how new, returning, and referral customers contribute to total revenue.

Summarize survey results

Present responses to simple yes or no or preference-based questions.

Pie charts work well when the main point is to understand what portion each segment contributes. They are most effective when the story is about ratio or share rather than granular comparison.

Using a Pie Chart in a Dashboard

Pie charts work best in combination with other visualizations. For example:

• Pair a pie chart showing quarterly product revenue with a bar chart displaying historical growth.
• Combine a pie chart showing where employees live with a map chart that adds geographic detail.
• Use a pie chart to summarize customer segments, then add a line chart to show how those segments change over time.

This approach keeps the pie chart focused on high-level insights while other charts provide depth and context.

Top Tips When Building a Pie Chart

Use these tips to improve readability and accuracy:

Avoid 3D charts

3D views distort slice sizes and make interpretation difficult.

Order slices from largest to smallest

Begin with the largest slice at the top, then move clockwise.

Limit the number of categories

Five or fewer categories is ideal. Group the rest into “Other.”

Label slices clearly

Use percentages or absolute values for clarity. People cannot easily compare area size without labels.

Pie charts remain a popular choice because they are easy to create, familiar to readers, and effective at showing simple part-to-whole stories.

Common Pie Chart Mistakes and Alternatives

Mistake: Too many slices

Use instead: A bar chart that compares values more accurately.

Mistake: Slices with very similar values

Use instead: A sorted bar chart or dot plot to highlight subtle differences.

Mistake: Using pies for time-based data

Use instead: Line charts or area charts.