Scatter plot with a third variable encoded as bubble size.
A free, animated bubble chart you can read here or embed on any website, from Scrollchart.
Bubble Chart
A bubble chart is a scatter plot extended to three variables. The horizontal axis encodes one numeric variable, the vertical axis encodes a second, and the radius of each circle (bubble) encodes a third. All three values must be read together to understand any single data point.\n\nThe convention of sizing bubbles by the square root of the third variable ensures that area, which the eye perceives, grows proportionally to the value rather than quadratically.
Bubble size is the hardest visual encoding to read accurately. Cleveland and McGill (1984) found that area is one of the least precise perceptual channels. Readers consistently underestimate the size ratio between large and small bubbles. Always include a size legend with two or three reference circles and their corresponding values.\n\nOverlapping bubbles are a common problem. Transparency helps reveal overlap but does not solve it. Color should be reserved for a fourth categorical variable.\n\nBubble charts work best with 10 to 30 data points. Above 30 to 40, overlap and clutter typically make the chart unreadable without interaction.
Graphical Perception: Theory, Experimentation, and Application to the Development of Graphical Methods , Cleveland, W. S., McGill, R. (1984) - Journal of the American Statistical Association, Vol. 79. Established the hierarchy of perceptual accuracy for visual encodings including area.
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Source & accuracy
This bubble chart is an editorial illustration built to represent the concept accurately. Where it shows figures, they are typical or representative values chosen to make the relationship clear, not a single underlying dataset. The diagram and its explainer are reviewed and maintained centrally, and updated over time as understanding improves.
Three dimensions encoded in scatter position and size
A bubble chart extends a scatter plot by encoding a third variable as bubble size. The x-axis and y-axis show two continuous variables; each point's position captures that pair; the bubble's diameter or area encodes a third variable. This lets you visualize three dimensions simultaneously. Bubble charts are used to compare countries (GDP vs life expectancy, sized by population), products (price vs customer rating, sized by sales volume), or any phenomenon with three quantitative attributes.
Reading bubble charts and avoiding false patterns
The size axis is challenging: our eyes misjudge bubble area, making a 2x area difference look smaller than it is. Color-coding bubbles by a fourth categorical variable (e.g., region) helps, but adding too many encodings creates visual clutter. Bubble charts work best when the size dimension is a multiplicative factor that merits its own axis (e.g., market capitalization) rather than a secondary annotation. When in doubt, a small multiples or faceted scatter plot (separate plots for subgroups) may be clearer.
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Reference
What this is
A free, embeddable, animated bubble chart for any website.
Who uses it
Data journalists, Researchers & academics, Content marketers, News organizations.
How to embed
Copy one line of HTML. No signup. No watermark. Works in WordPress, Webflow, Ghost, Substack, plain HTML.
File size
iframe embed, ~80 KB gzipped (loads on demand, does not block your page paint).
License
Free forever. Editorial explainer text included; updated centrally over time.
Copy the universal HTML snippet, the WordPress shortcode, or an iframe fallback -
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Frequently asked questions
Where can I get a free animated "Bubble Chart" for my website?
Scrollchart provides "Bubble Chart" as a free, embeddable animated diagram you can add to any website with one line of HTML. No signup is required and there is no watermark. The diagram and its explainer text are served from scrollchart.com, so the embed stays current without any maintenance on your end.
How do I embed a bubble chart in a blog post or article?
Paste the one-line HTML snippet from the Scrollchart diagram page into your post editor. It works in WordPress, Webflow, Ghost, and plain HTML with no plugin required. The animated diagram and its explainer text load from scrollchart.com and render directly in your page DOM.