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Polar chart

One series across cyclic categories: angle is the category, radius the value.

1 polar chart example

Daily demand profile

Request volume by three-hour window, as a percentage of the daily peak.

Angle is the time of day and radius is the magnitude, so the shape of a day reads at a glance. Rays are lollipops, never filled wedges, because area would exaggerate the peak the accent already points at.

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What is a polar chart?

A polar chart plots values on a circular grid: the angle represents a category, often a cyclic one like hours of the day or months, and the distance from the center represents the value. Florence Nightingale's polar area diagram of 1858 is the famous early example.

Read it around the circle like a clock. Longer bars or points farther from the center are higher values, so peaks and quiet periods in a daily or yearly cycle stand out.

When to use a polar chart

  • Use it to show a daily demand profile, such as orders by hour, where midnight wraps back to the start.
  • Use it for seasonal patterns by month or wind and direction data.
  • If the categories are not cyclic or you need precise comparisons, a bar chart is easier to read accurately.

How to make a good polar chart

  1. Use it only for categories that wrap around naturally.
  2. Start at the top, at 12 o'clock, and go clockwise, as readers expect.
  3. Keep radial gridlines light and label a few values so magnitudes can be estimated.
  4. Highlight the peak and keep the rest of the series neutral.