Radar Charts
GUIDEWhat a radar (spider) chart shows, when to use one, how to read it, and the traps to avoid.
A radar chart — also known as a spider chart, star chart, or polar chart — plots several variables on separate spokes that radiate from a single center point. Each spoke is its own axis, the value on that axis is marked as a point, and the points are joined into a closed shape. The result is a compact "profile" of one thing measured across many dimensions at once, which makes radar charts a favourite for comparing multi-attribute items where the overall shape matters more than any single number.
How a radar chart works
Imagine a wheel. Every variable you want to measure gets its own spoke, spaced evenly around the circle. The center of the wheel is the lowest value (often zero) and the outer rim is the highest. For each variable you place a point along its spoke at the right distance from the center, then connect all the points to draw an enclosed polygon. The concentric rings drawn behind the spokes act like the gridlines of a normal chart, giving you reference levels to read against.
Because every axis shares the same center, you can overlay a second or third series on the same wheel — each drawn as its own coloured shape — and compare their profiles directly. Where one shape bulges outward, that item scores higher on that variable; where it pulls in toward the center, it scores lower. The eye reads the silhouettes, which is exactly what makes the format so good for "at a glance" comparison and so risky for precise reading.
When to use a radar chart
- Comparing profiles across several dimensions. Rating a few products, candidates, or teams on the same set of attributes — speed, cost, quality, reliability, and so on — where you want to see strengths and weaknesses as a shape.
- A small number of items. One to three overlaid series stay readable. Beyond that the shapes overlap into a tangle.
- Variables on a common scale. Scores out of ten, percentages, or ratings that all run in the same direction work cleanly because the rings mean the same thing on every spoke.
- The pattern is the message. "This option is balanced; that one is spiky" is a takeaway a radar chart delivers instantly.
If your takeaway is "these two items have different shapes — one is strong here, weak there," a radar chart fits. If it is "item X scores exactly 3 points higher on this one attribute," reach for a bar chart instead.
When not to use a radar chart
Radar charts attract criticism, and most of it is deserved when they are stretched past their comfort zone:
- Too many axes. With a dozen or more spokes the polygon becomes a jagged blob and the labels crowd each other. Three to about eight variables is the practical sweet spot.
- Too many series. Overlay four or five shapes and they cover one another; you can no longer tell which line belongs to which item.
- Precise comparison. People judge the length of a straight bar far more accurately than the position of a point on a slanted spoke. Small differences are easy to miss.
- Non-comparable scales. If one axis runs 0–10 and another runs 0–1,000,000, the rings are meaningless and the shape is an artefact of the scaling, not the data.
How to read a radar chart
Start at the center and read outward: the further a point sits from the middle, the higher its value on that axis. Check the rings first so you know what each level represents, then trace the shape spoke by spoke. To compare overlaid series, look for where one shape sits outside the other — that is a genuine advantage on that variable — and where they cross. Pay attention to overall balance: a near-circular shape means even scores across the board, while a spiky shape means strong on a few axes and weak on others. Use the value labels for anything that looks close, because your eye will only estimate positions on the spokes.
Variants
The most common variant is the filled radar, where each shape is shaded with a translucent colour so overlapping profiles are still visible — the version drawn above. A line-only radar omits the fill, which keeps several series legible when their shapes cross often. A polar area chart is a cousin in which each variable becomes a wedge whose radius (not angle) encodes the value; it looks similar but is read more like a pie. Whichever you choose, keep the axis order and scale consistent so the comparison stays honest.
Common mistakes to avoid
Area distortion: the filled area grows with the square of the values, so a profile that scores a bit higher on every axis looks dramatically larger than it really is. Reordering the axes changes the shape entirely without changing a single number, so the same data can be made to look "rounder" or "spikier" — fix the order deliberately. Mixing incompatible scales on different spokes produces a shape that means nothing. And too many overlaid series turns the chart into an unreadable web.
Make a radar chart
Ready to build one? The radar chart maker lets you name your axes, enter values for one or more series, recolour and fill the shapes, and export a PNG or SVG — free, no signup, no watermark.