What a pie chart needs from your data
A pie chart shows parts of one whole. Your data needs two columns. The first column holds labels, such as department names or survey answers. The second column holds numbers, such as counts or dollar amounts. Each number is a part of the same total. One row per slice.
Paste the two columns straight from Excel, Google Sheets or Numbers. The tool finds the delimiter by itself: a tab if any line has one, otherwise a comma, semicolon or pipe, whichever splits the lines most consistently. A first row is treated as headings only when the rows below it are numbers or dates and the first row is not. Rows with fewer columns than the widest row are padded, and the count is reported, never dropped.
If your numbers are not parts of one whole, stop here. A pie chart of five unrelated totals tells the reader nothing useful. Use the bar graph maker instead.
How the percentages are worked out
Each slice's percentage is its value divided by the total of all values, times 100. The tool shows the total on the page so you can check the arithmetic yourself. If the percentages do not add to 100, rounding is the reason, not a bug.
Here is a worked example. Suppose you paste four rows: Rent 1200, Food 600, Transport 400, Savings 800. The total is 3000. Rent is 1200 / 3000 = 40%. Food is 600 / 3000 = 20%. Transport is 400 / 3000 = 13.3%. Savings is 800 / 3000 = 26.7%. The four percentages add to 100%.
Numbers are read carefully. A trailing per cent sign is dropped, not divided, so 45% charts as 45. Currency symbols, trailing units and spaces are ignored. A value in parentheses is negative, as accountants write it. Empty cells and spreadsheet errors like #DIV/0! are counted as empty, not as zero, so one n/a cannot turn a column of numbers into a column of text.
When a pie chart is the wrong tool
People judge angles poorly. In Cleveland and McGill's ranking of how accurately people read graphical elements, judging position along a common scale is the most accurate task and judging angle or area is markedly less accurate [Cleveland & McGill 1984]. Heer and Bostock replicated that ranking with a larger crowdsourced sample [Heer & Bostock 2010].
That research points to four cases where you should pick something else:
- More than about six slices. The angles get too small to compare.
- Values that are not parts of one whole. A pie chart implies a total that may not exist.
- Two pies compared side by side. Readers cannot compare angles across two circles.
- Slices of similar size. A 24% slice and a 26% slice look the same.
In all four cases, a bar chart is the better choice, because bar length is easier to read than slice angle. The bar graph maker takes the same two columns. If your data is one column of numbers and you want to see its shape, use the histogram maker instead. If your data changes over time, use the line graph maker. If you have two measurements per observation, use the scatter plot maker.
Donut charts, sorting and labels
A donut chart is a pie chart with the middle cut out. The slices work the same way, and the percentages are worked out the same way. The hole gives you space for a total or a short label. The trade-off is the same as a pie: readers still judge angles, so the six-slice limit still applies.
You can sort slices largest first. That puts the biggest share at the top and makes the order easy to scan. Sorting does not change any percentage, only the position of the slices.
The tool draws the percentage on each slice. You do not have to calculate them by hand or add them in a separate step. The total is shown too, so a reader can check that the parts add up.
When you download, you get PNG at twice the chart's size, so it stays sharp in a document or a slide. You also get SVG, which stays sharp at any size and can be opened and edited in Illustrator, Inkscape, Figma or Word. There is no watermark, no sign-up and no limit on the number of charts. The chart carries a title and a description in the file itself so a screen reader can announce it, and the figures behind every chart are also shown as a table on the page, because a chart is an image and an image needs a text equivalent [WCAG 2.2, success criterion 1.1.1].
The chart is drawn by code running in your own browser. Pasted text is read in the browser and is never sent to a server. The "copy link to this chart" link carries the data in the fragment of the URL, the part after the # that browsers do not transmit to a server. A link has a practical length limit of about 7,800 characters, and the page says plainly when a dataset is too large to share that way. Charts are not stored on this site.
For the full references and the rules behind the scales, see how it works.