Foundations · Charts
Pie Chart Calculator
Turn values into a pie — each slice's percentage and its angle in degrees — drawn for you. And, because slices are genuinely hard to compare by eye, the very same data is shown as a bar chart right beside it. Use the pie to show one part of a whole; reach for the bar the moment you actually need to rank or compare.
Each value becomes a slice. Labels are optional. Values should be parts of a single whole (a budget, a vote share) — that is the only thing a pie chart is good for.
Result
In plain English
A pie chart shows how a single total splits into parts: each slice's angle is its share of 360°. It does one job well — “this is roughly half, that is a sliver” — and almost everything else badly, because people read angles and areas far less accurately than lengths. When the question is “which is bigger?” or “by how much?”, a bar chart answers it at a glance where a pie makes you squint.
- percentage
- Each value as a share of the total: value ÷ total × 100. All the slices add to 100%.
- angle (degrees)
- The slice's share of the full circle: value ÷ total × 360°. All the angles add to 360°.
- why a bar chart too
- Lengths on a common baseline are the easiest thing for the eye to compare, so the bar chart makes differences between categories obvious that the pie blurs.
- when a pie works
- A few slices (ideally two to five), parts of one genuine whole, and the goal is a rough sense of proportion — not precise comparison or ranking.
- when it misleads
- Many thin slices, similar-sized slices, values that don't sum to a meaningful whole, or any 3-D / exploded effect — all distort the proportions the chart is meant to show.
Frequently asked
How do I calculate the angle of a pie chart slice?
Each slice's angle is its share of the full 360°: angle = (value ÷ total) × 360°. So a category worth 25 out of 100 gets (25 ÷ 100) × 360° = 90°, a right angle — a quarter of the pie. Its percentage is the same fraction times 100, here 25%. All the slice angles add up to 360° and all the percentages to 100%.
When should I not use a pie chart?
Avoid a pie when you need to compare categories or read values precisely — the eye judges slice angles poorly, especially for similar sizes. Avoid it with many categories (more than about five becomes a confetti of slivers), when the parts don't add up to a meaningful whole, or when you would be tempted by a 3-D or exploded look, which distorts the areas. In all these cases a bar chart is clearer and more honest.
Why does the same data look clearer as a bar chart?
Because of how human vision works. We compare lengths along a shared baseline very accurately, but angles and areas much less so. A pie asks you to compare angles; a bar chart asks you to compare lengths. That is why two slices that look almost equal in a pie can be visibly different bars — and why the bar version is the safer default whenever exact comparison matters.
How many slices is too many for a pie chart?
Beyond about five or six, the slices become slivers no one can tell apart, and the smallest categories vanish into the rim. If you have more, group the small ones into a single “Other” slice — or, better when the goal is comparison, switch to a bar chart, which stays readable with dozens of categories and lets the eye rank them at a glance.