Pie Chart
Pie/donut chart from worksheet columns or manual data
Anatomy of a Pie Chart
A pie chart shows how a whole is split into a few categories. Each category is drawn as a circle slice with an area proportional to its share. Together all slices add up to exactly 100 %.
Slice: A pie slice whose angle (and therefore area) is proportional to the category share of the total. Slices are typically sorted from largest to smallest, starting at "12 o'clock".
Labels: Each slice can be labeled with the category name, absolute value, percentage, or a combination. Very small slices are often labeled outside the circle.
"Other" slice: When there are many small categories, it is sensible to group them into "Other", otherwise the chart becomes cluttered. A healthy pie chart typically has no more than 5–7 slices.
Pie charts are appropriate for communicating the share of a few clearly distinguishable categories of a whole — e.g. "How does our scrap split across the five defect types?".
Pitfalls
Too many slices: More than 7 slices become visually indigestible and small shares are hard to distinguish. Prefer a Pareto chart — it additionally orders categories by size.
Poor size comparison: The human eye estimates angles and areas poorly. Differences of a few percentage points are barely visible in pie charts. For precise comparisons, use a bar chart.
3D effects distort: 3D pie charts distort slice areas — front slices look larger than they are. For honest visualization, prefer 2D.
Shares do not add up to 100 %: When categories allow multiple assignments (e.g. "defects with cause A or B"), pie charts are misleading. They assume that categories are mutually exclusive.
Comparing several pie charts: Comparing two pie charts side by side is hard — slices move and change order. For comparisons across time or groups, use stacked bars instead.
Examples
This module ships with the following example datasets — load any of them in the app with a single click.