Pie Charts
GUIDEWhat a pie chart shows, when to use one, how to read it, and the traps to avoid.
A pie chart is a circle divided into slices, where each slice's angle shows one category's share of a whole. Use a pie chart when you have one total split into a few parts (about six or fewer) that add up to 100%, and the message is a simple share, such as one part dominating.
A pie chart is one of the most recognisable charts there is: a circle sliced into wedges, where each wedge represents a category's share of the whole. It answers a single, specific question — how is one total divided among its parts? — and when used for exactly that, it communicates instantly.
How a pie chart works
The full circle — 360 degrees — represents 100% of the total. Each category gets a slice whose angle is that category's share of the total. A category worth 25% of the whole takes a quarter of the circle (90°); a category worth 50% takes a semicircle. Because the slices are cut from the same circle, the reader can see at a glance which categories are large and which are small, and that everything sums to one complete whole.
That last point is what separates a pie chart from a bar chart. A bar chart compares independent quantities; a pie chart specifically shows composition — parts of a single thing. If your categories are not parts of one whole, a pie chart is the wrong tool.
When to use a pie chart
- One whole, a few parts. Budget split across 3–5 categories, market share among the top players, survey responses to a single question.
- The message is "this part dominates." Pies excel at showing that one slice is clearly the biggest, or that the split is roughly even.
- Precision is not the goal. If readers only need the gist — "most of the budget goes to salaries" — a pie communicates that faster than a table.
If you can phrase your takeaway as "X is [a fraction] of the total," a pie chart fits. If your takeaway is "X is bigger than Y by [an exact amount]," reach for a bar chart instead.
Pie chart checklist
Before you draw a pie, run your data through these four questions. If any answer is no, a bar chart or stacked bar chart will almost always serve you better.
| Question | Pie works if |
|---|---|
| Do the values make up one whole? | Yes, they sum to a meaningful total or 100% |
| Are the categories mutually exclusive? | Yes, nothing is counted twice |
| How many categories are there? | About two to six |
| Is it one moment in time? | Yes, a single snapshot |
Example: "What share of tickets were cancelled vs confirmed?" passes every test: two categories, one whole, one period. A pie (or a single 100% bar) is a good fit. "How did cancellations change month by month?" fails the last test, so a line chart is the right choice. For a fuller side-by-side, see pie chart vs bar chart.
When not to use a pie chart
Pie charts get criticised, and usually it is because they were used for a job they are bad at:
- Many categories. Past about six slices, the small ones become slivers that are impossible to label or compare. Group small categories into an "Other" slice, or switch to a bar chart.
- Precise comparison. People judge the lengths of bars far more accurately than the angles of slices. Two slices of 24% and 27% look identical in a pie but are clearly different as bars.
- Change over time. A pie is a single snapshot. To show how a composition shifts across periods, use a line chart or a stacked bar chart.
- Values that are not parts of a whole. Comparing the populations of five unrelated cities is not a composition — those are independent quantities, so use bars.
How to read a pie chart
Start with the largest slice and work down — pies are easiest to read when slices are ordered by size, usually clockwise from the top. Compare each slice to familiar reference angles: a half circle is 50%, a quarter is 25%, and an eighth is around 12%. Use the labels or legend for exact figures, because your eye will only estimate the angles. If two slices look close in size, trust the numbers rather than the picture.
From percentages to slice angles
A full circle is 360°, which stands for 100% of the data, so each 1% is 3.6°. Multiply a percentage by 3.6 to get its slice angle. For raw values, divide each value by the total and multiply by 360.
| Share | Angle | Looks like |
|---|---|---|
| 10% | 36° | A thin wedge |
| 12.5% | 45° | One eighth |
| 25% | 90° | A quarter (right angle) |
| 30% | 108° | A bit more than a quarter |
| 50% | 180° | A half |
| 75% | 270° | Three quarters |
Worked example: a class of 40 students picks favourite sports: 18 football, 12 basketball, 10 tennis. Football is 18 ÷ 40 = 45%, so 45 × 3.6 = 162°. Basketball is 30%, or 108°. Tennis is 25%, or 90°. Check: 162 + 108 + 90 = 360°. The pie chart angle calculator does this conversion for any list of values.
Data vs data labels on a pie chart
The two terms are easy to mix up. The data are the numbers behind the chart; they decide how big each slice is. A data label is the text attached to a slice that reports something about it: the raw value (18), the percentage (45%), the category name (Football), or a combination. A legend is a separate key that matches colours to category names.
- Prefer direct data labels on or next to each slice over a legend, so readers do not have to look back and forth.
- Show percentages when the share is the point, and raw values when readers need the actual counts. Showing both is fine for a small number of slices.
- Round percentages consistently, and make sure labels still add up to 100% (or note the rounding).
Pie vs. donut charts
A donut chart is simply a pie chart with a hole in the centre. The proportions are read exactly the same way — the hole changes nothing about the data. Its one practical advantage is the empty middle, which can hold a total or a label. Choose whichever looks cleaner for your context; neither is more "correct." The donut chart guide covers the trade-offs in detail.
Common mistakes to avoid
3-D pies tilt the circle, distorting the angles readers rely on — avoid them. Exploded slices pulled away from the centre make sizes even harder to compare. Slices that don't sum to 100% mean your categories aren't a true whole. And rainbow colour schemes with no order make the chart harder, not easier, to read.
Make a pie chart
Ready to build one? The pie chart maker lets you enter labels and values (or paste a CSV), switch between pie and donut, recolour slices, and export a PNG or SVG — free, no signup, no watermark.
Frequently asked questions
When should you use a pie chart?
Use a pie chart when you are showing how one whole divides into a few parts, ideally six or fewer, the values add up to 100 percent, and the main point is the rough share of each part, such as one slice dominating. For precise comparisons, many categories or change over time, use a bar or line chart.
What is the difference between data and a data label on a pie chart?
The data are the underlying values that set each slice's size. A data label is the text printed on or beside a slice to show that value, its percentage, or its category name. Changing a label changes only the text, never the size of the slice.
Is a pie chart worse than a bar chart?
Not always. A bar chart is better for comparing precise values or many categories, because lengths are easier to judge than angles. A pie chart is fine, and quicker to read, when there are only a few parts of one whole and the message is a simple share such as about three quarters.
How do you turn a percentage into an angle on a pie chart?
Multiply the percentage by 3.6, because 100 percent equals 360 degrees. For example, 25 percent is 90 degrees and 30 percent is 108 degrees. For raw values, divide each value by the total and multiply by 360.
What is the difference between a pie chart and a donut chart?
A donut chart is a pie chart with the center removed. The data and proportions are identical; the hole is purely stylistic and can hold a label or total. Both are read the same way.
Do pie chart values have to add up to 100%?
Yes, conceptually. A pie represents one whole, so the slices should sum to the total. You can enter raw counts and let a tool convert them to percentages, but the categories must be mutually exclusive parts of the same whole.