What is an area chart?
An area chart fills the space below a line chart so that "area" expresses volume. It shows the trend with a line while also conveying accumulated magnitude visually, which makes it ideal for situations where you want readers to feel the size of a quantity changing over time.
Where a line chart shows only the movement of the line itself, an area chart shows movement plus the accumulated volume underneath. Perfect when you want a sense of magnitude alongside a trend in traffic or sales.
When to use it
Tips for making one well
1. Limit to about three series
Because the fills overlap, area charts get harder to read with more series. Beyond three, consider stacking or switching to a line chart.
2. Mind the transparency
When series overlap, lowering the fill opacity makes the series behind easier to read.
3. Put the main series on top
Adjust the draw order so the series you want to highlight isn't hidden behind the others. Setting its color a touch darker also helps it stand out.
4. Start the Y-axis at zero
Since area encodes magnitude, the Y-axis must start at zero. Starting partway up exaggerates the area itself.