Area Charts
GUIDEWhat an area chart shows, when to use one, how to read it, and the traps to avoid.
An area chart is a line chart with the space beneath the line filled in. Like a line chart it plots a value against a continuous axis — almost always time — and connects the points to show a trend. The difference is the shading: by colouring the region between the line and the baseline, an area chart shifts the emphasis from the path of the value to the cumulative magnitude underneath it. The filled volume reads as "how much," which makes the format well suited to quantities that accumulate, like totals, volumes, or amounts that pile up over a period.
How an area chart works
The horizontal axis carries an ordered, continuous variable — usually a sequence of dates or periods. The vertical axis carries the measured value, and it should start at zero. Each data point is plotted and the points are joined into a line; then everything between that line and the zero baseline is filled with colour. Because the fill represents area, the baseline matters more than it does in a plain line chart: if the axis starts above zero, the shaded region no longer reflects the true quantity and the chart misleads.
That single change — the fill — is the whole difference. Reach for the fill when the quantity beneath the curve is meaningful in itself ("total visitors," "cumulative rainfall," "stockpiled units"). Keep to a plain line when only the line's position and direction matter and the area underneath has no real meaning.
When to use an area chart
- Magnitude over time. A single series where the volume under the curve genuinely represents an accumulated quantity you want readers to feel.
- Parts of a whole over time. A stacked area chart shows how several components add up to a changing total across periods — both the total and each part's contribution at once.
- Emphasising scale. When you want a trend to read as "big" or "small" in absolute terms, the filled mass communicates that more forcefully than a thin line.
If the space under the line means something — a total, a volume, a running amount — fill it. If only the line's position matters, or you are comparing several series closely, a plain line chart reads cleaner.
When a plain line is better
The area fill is not free; it competes for attention and can hide data. A plain line chart usually wins when:
- You are comparing several series. Multiple overlapping filled areas obscure one another — the back series disappears behind the front one. Separate lines stay distinct.
- The values can go negative or fluctuate sharply. A fill across a zigzag becomes visual noise rather than a clean trend.
- The area has no real meaning. Charting a temperature or a price, the region "under" the value is not a quantity, so filling it adds ink without adding information.
- Precise readings matter. The eye locks onto the top edge of an area just as it would a line, but the fill adds clutter that makes exact values harder to pick out.
How to read an area chart
Read the top edge of the shaded region exactly as you would a line: follow it left to right to see the trend, noting where it rises, falls, or plateaus. The height at any point is the value at that moment, read off the vertical axis. The filled mass beneath is a cue to overall magnitude — a tall, wide fill means a large accumulated quantity. In a stacked area chart, the height of each band (not its top edge) is that series' value, and the top of the whole stack is the running total. Use gridlines and labels for exact figures, since the fill makes eyeballing precise values harder.
Variants
The simple area chart shades a single series down to zero. The stacked area chart layers several series on top of one another so their bands sum to a total — ideal for parts-over-time, as long as you remember each band is measured from the one below it, not from zero. The 100% stacked area chart rescales every period to fill the full height, trading absolute totals for a clear view of how the proportions shift. And a streamgraph is a stacked area centred on a flowing middle baseline, which looks striking but sacrifices easy value reading.
Common mistakes to avoid
A non-zero baseline distorts the very area the chart is built on — always start at zero. Overlapping opaque areas hide the series behind them; if you must overlay, use a plain line chart instead, or make the fills translucent. Too many stacked bands make it impossible to track any single series, because each one shifts up and down with the bands below it. And reading a stacked band's top edge as its value is a classic error — only the bottom band is measured from zero.
Make an area chart
Ready to build one? The line chart maker includes an area mode — enter your data or paste a CSV, switch the fill on, layer multiple series, recolour, and export a PNG or SVG — free, no signup, no watermark.