Pie and donut charts

Best for

Showing how one clear whole splits into two or three parts, such as yes versus no answers or the share of mobile traffic.

Avoid when

You have more than about four slices, the slices are similar in size, or you need to compare several wholes.

Data you need

One categorical column and one numeric column whose values add up to a meaningful total.

A pie chart shows how a whole divides into parts, with each slice's angle (and area) proportional to its share. It's fine when there are two or three parts of a whole everyone understands, such as yes and no answers to a survey question, or the share of support tickets that got solved.

Past that, pies get hard to read fast. People judge angles and areas much less accurately than lengths, so with five or more slices of similar size, readers can't rank them without the labels. At that point, a sorted bar chart does the job better.

When a pie is fine

A pie works when all of these are true:

• The parts add up to a meaningful whole (100% of survey replies, all of the budget).
• There are only two or three parts, maybe four if one is tiny.
• The parts are clearly different in size, so ranking them takes no effort.
• The message is about a share of the whole, like "almost two thirds said yes."

People do have a decent sense of a few familiar fractions. A half, a quarter and a third are easy to spot in a pie, which is why a 62/38 split reads quickly. The pie also says "these parts form one whole" more directly than bars do. That is its real advantage, and it is worth using when it fits.

Why many slices fail

Add more slices and every weakness shows. Angles are hard to compare unless they share an edge, small slices become slivers, and labels pile up around the rim with leader lines. With similar-sized slices, the reader can't tell which is bigger without reading every number.

Seven colors also mean seven entries to match, whether in a legend or around the edge. Bars need one color, and their labels sit right next to them.

A few other pie habits make things worse:

• 3D pies tilt the circle, so slices at the front look bigger than equal slices at the back. Never use them.
• Exploded slices (pulled out from the center) break the shape and make angles harder to judge.
• Several pies side by side, one per year or region, ask readers to compare angles across separate circles, which almost nobody can do accurately. Use a 100% stacked bar chart instead.

Donut charts

A donut is a pie with the center removed. Without a center point, readers judge slices by arc length instead of angle. Perception research suggests this works about as well as a pie, not better or worse in any big way.

The hole is useful, though. It can hold the total ("1,240 tickets") or the headline share, which puts the key number right where the eye lands. Donuts also look less heavy on dashboards, and a thin ring can show a single progress-style share, like 71% of a goal reached.

All the pie rules still apply. Two or three parts, clear differences, labels next to the arcs rather than in a legend. A donut with eight segments is just as hard to read as a pie with eight slices.

Making a pie work

When a pie is the right call, a few details keep it clean:

1. Start the first slice at 12 o'clock and go clockwise. Readers expect this.
2. Order slices from largest to smallest, unless the categories have a natural order (like survey answers), in which case keep that order.
3. Label slices directly with the name and the percentage. Skip the legend.
4. Use one strong color for the slice you are talking about and muted colors for the rest.
5. Merge tiny slices into "Other", and make sure the percentages add up to 100. If rounding gives 99 or 101, note it or adjust.

Rule of thumb: if you need a legend to read your pie, you have too many slices.

Better alternatives

A sorted bar chart is the default answer. It handles any number of parts, shows small differences, and leaves room for labels. You lose the visual hint that the parts form a whole, so add it in the title: "Share of visits by source (total 100%)."

A waffle chart, a 10 by 10 grid of squares where each square is 1%, is another option for one or two shares. It's easy to count and works well for general audiences ("23 in every 100 users").

Common mistakes

Pies earn their bad reputation from the cases above. Used for a simple split of a clear whole, they're quick to read and hard to get wrong.