Last updated 3 September 2026
Bar or pie
Bar charts make it easy to compare exact sizes between items side by side. Pie charts show how parts relate to a whole, and read best when there aren't too many slices — past about six, the smaller wedges become hard to tell apart. Both update live as you edit the data, so it's easy to try both and see which makes the point more clearly.
Choosing the right chart type
Most confusing charts are the result of picking a shape that does not match the question. A bar chart compares distinct categories and is almost always the safest default — the eye reads bar length precisely, and categories that are not in a natural order can be sorted by value to make the ranking obvious. A line chart shows change over a continuous scale, which in practice nearly always means time; the connecting line implies that the space between points is meaningful, so using one for unordered categories misleads the reader.
A pie chart shows parts of one whole and only works when the slices sum to 100% and there are few of them. Beyond about five segments the wedges become impossible to compare by eye, and a sorted bar chart communicates the same data better. If two slices are close in size, a reader genuinely cannot tell which is larger.
Making a chart readable
Bar charts should start at zero. Truncating the axis exaggerates differences dramatically — a change from 98 to 102 looks like a fourfold jump if the axis begins at 97, and that visual impression is what people remember rather than the numbers. Line charts have more latitude here, because they show change rather than magnitude, but the axis range should still be stated clearly.
Beyond that, the useful discipline is subtraction. Label the axes so the units are unambiguous, drop the legend if there is only one series, and avoid using colour to encode something that a direct label would say better. A chart with fewer elements almost always reads faster than one with more.
Common questions
What format does the data need to be in?
One item per line, written as "Label, Value" — for example "January, 4200". Lines that don't match this pattern, or have a negative or missing number, are skipped rather than breaking the chart.
When should I use a bar chart instead of a pie chart?
Bar charts are easier to read when comparing exact sizes between items. Pie charts work best when the numbers are parts of one whole and the proportions, not the exact values, are the point — they get hard to read past about six slices.
Is my data uploaded anywhere?
No. The chart is drawn entirely on an HTML canvas in your browser. Nothing you type is sent anywhere.
When should I use a bar chart instead of a line chart?
Use bars for comparing distinct categories, and a line when the horizontal axis is continuous — usually time. A line implies that the space between points is meaningful, so joining unordered categories with one suggests a trend that does not exist.
Why do pie charts get criticised so often?
Because people judge angles and areas far less accurately than lengths. With more than about five slices, or with two slices of similar size, readers genuinely cannot tell which is larger. A sorted bar chart shows the same data more precisely.
Should the axis always start at zero?
For bar charts, yes — bar length is the whole message, and truncating the axis exaggerates small differences into large-looking ones. Line charts showing change over time have more latitude, but the range should be labelled clearly so the reader can judge the scale.