Use bars instead of pie or donut slices for percentage comparisons
For comparing shares across categories, prefer bar charts over pie or donut charts to improve readability and mitigate hard-to-see percentage differences for general audiences.
- purpose:select
- basis:heuristic
- chart:bar:use
- chart:pie-donut:avoid
- operator:part-whole
- reading-mode:exact
- lever:chart-family
- quality:readability
advice
Bar encoding for shares
Replace circle sectors with bars when readers need to compare percentages across categories. For example, show election results as bars instead of a pie or donut when small gaps such as a 3 percentage-point difference should be easy to see.
reason
Why bars make percentage gaps easier to see
Aligned lengths are easier to compare than circle sections. Small differences that nearly disappear in a pie or donut become visible in bars.
Mechanism: Bars put percentages on a common baseline, making gaps and ranking easier to judge than with angles or arc lengths.
Evidence: Pie, donut, and parliament charts clearly signal that the values are percentages, but circle sections are described as not easy to compare, while a 3% difference is easy to spot in a bar chart and practically invisible in a pie or donut (Muth, 2025).
context
Use when percentage comparison is the main job
- User Goal: Compare category shares or rank categories by percentage.
- Task: Detect small differences between percentages.
- Data: One percentage value per category.
- Chart Setting: A share chart where the reader needs comparison more than decoration.
- Audience: A mainstream audience.
- Success Criterion: Small percentage gaps are easy to spot.
exceptions
Do not use when the main need is only to signal that values are percentages
Break it when: Fine comparison is not important and the chart mainly needs to make clear that it is showing shares rather than absolute numbers. Why: Pie and donut charts state that percentages are being shown very obviously.
costs
Costs of replacing circle sectors
Sacrifice: You lose the immediate visual cue that the display is about percentages rather than absolute totals.
Risk: If exact comparison is not the real task, the swap may not add much.
Mitigation: Make the switch when the key message depends on comparing percentage differences.
mistakes
Common failure with share charts
Mistake: Keep a pie or donut chart when the reader must spot small differences between categories. Why it fails: Circle sections make close percentage comparisons hard to see.
check
Check whether the share chart supports comparison
Failure Sign: Small percentage differences are hard to judge in the pie or donut.
Quick Check: Build both a bar version and a pie or donut version of the same percentages; if the bar version makes the key ranking or gap obvious, use bars.
Stronger Test: Ask whether a reader can reliably tell which category is slightly larger without reading every number.
fix
Fix the share comparison
- Replace the pie or donut with a bar chart.
- Keep the same percentage values and compare them as aligned lengths.
- Reserve the pie or donut form for cases where exact percentage comparison is not the point.