How to Make a Bubble Chart (Three Variables at Once)
Learn how a bubble chart shows three variables at once, when to use one, how to set up your data and make it, with a free bubble chart maker.
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Free tool: Bubble Chart MakerA bubble chart is a scatter plot with a third dimension: each point is a bubble whose size shows another value. Price on one axis, customer rating on the other, and units sold as the size of each bubble, for example, lets you see three things about every product at a glance. This guide explains when a bubble chart helps, how to read and set one up, and how to make one with the free Bubble Chart Maker.
When to use a bubble chart
Bubble charts are useful when:
- You're comparing items on two measures and want to show how big each one is, such as products by price, rating and sales.
- You're looking for standouts: a large bubble in an unusual position, such as a cheap product that sells far more than expected.
- You have a modest number of items, roughly 5 to 30. With more, the bubbles overlap and the chart gets cluttered.
If you only have two variables, a scatter plot is simpler. If you're comparing amounts across categories, use a bar graph.
How to read a bubble chart
- Horizontal position shows the first variable (x).
- Vertical position shows the second variable (y).
- Bubble size shows the third variable (z).
People compare bubbles by their area, so bubble sizes should be scaled by area rather than width; otherwise a value twice as large looks four times as big. The Bubble Chart Maker scales the area of each bubble, which keeps the comparison fair. Even so, people judge areas less precisely than positions, so put your most important variable on an axis and use size for the third.
Example: five products
| Product | Price ($) | Rating (out of 100) | Units sold |
|---|---|---|---|
| A | 10 | 15 | 100 |
| B | 20 | 28 | 250 |
| C | 30 | 12 | 80 |
| D | 40 | 40 | 400 |
| E | 50 | 35 | 180 |
Plotted with price on the x-axis, rating on the y-axis and units sold as bubble size, product D stands out at once: high-priced, highly rated and the biggest seller.
How to make a bubble chart with Graph Maker
- Open the Bubble Chart Maker. It runs in your browser, with no sign-up.
- Add a chart title and axis titles, such as "Price, Rating and Sales", "Price ($)" and "Rating".
- Enter the X values, separated by commas:
10,20,30,40,50. - Enter the Y values in the same order:
15,28,12,40,35. - Enter the bubble size values in the same order:
100,250,80,400,180. The first X, Y and size values make the first bubble, and so on. - Pick the colors of the bubbles, background, title and text.
- Download the chart as a PNG, JPG or SVG.
Hover over a bubble to see its exact values.
Tips for a clear bubble chart
- Explain the bubble size. Mention it in the title or a note, such as "bubble size = units sold", because there's no axis for it.
- Keep the number of bubbles manageable. Overlapping bubbles hide each other; show the most important items and leave out the rest.
- Use size for positive amounts only, such as sales, population or budget. Negative values can't be shown as a size.
- Name the standout bubbles in your text, since the chart doesn't label each bubble.
Frequently asked questions
What is a bubble chart used for?
Comparing items on three numeric measures at once, two shown by position and one by bubble size, such as products by price, rating and sales, or countries by income, life expectancy and population.
What's the difference between a bubble chart and a scatter plot?
A scatter plot shows two variables with points of equal size; a bubble chart adds a third variable by changing the size of each point.
How many bubbles should a bubble chart have?
Usually no more than about 20 to 30. Beyond that, the bubbles overlap and the chart becomes hard to read.