Area Chart: Baselines, Cumulative Values and Multiple Series

An area chart shades the region beneath a line, giving the size of a series more visual weight. It can be useful for showing storage used, cumulative revenue or another quantity whose level matters alongside its changes. Check what the numbers mean first: shading monthly sign-ups does not turn them into a running total.

What the shaded region represents

An area chart is simply a line chart with the region between the line and the axis shaded in. The filled region draws attention to the level of the values relative to the baseline. Its meaning still comes from the plotted data and labels, not from the fill alone. It suits cumulative totals, such as revenue to date or total users, and quantities where the volume itself is the story, like storage used or hours worked per week.

Because the eye judges the shaded area, an area chart must start at zero. A line chart can sometimes zoom into a narrow band to show a small but real change; an area chart that does the same exaggerates the volume badly.

When a line chart is the better choice

If you are comparing several series that cross each other, lines win. Two overlapping filled areas hide each other, and transparency only half solves it. If the values swing up and down rather than accumulate, the fill adds visual weight without adding meaning. If your audience needs exact values at specific points, provide value labels or a data table rather than asking readers to estimate them from either chart.

A reasonable default: start with a line chart, and switch to an area chart only when you catch yourself wanting people to notice how big the total is.

Stacked area charts and their limits

Stacking areas on top of each other shows how a total is made up over time, such as traffic split by channel. The top edge is the total and the bands show the parts, which is genuinely useful. The trap is the middle bands. Only the bottom band sits on a flat baseline, so every band above it has a wavy floor, and changes are harder to compare against a consistent baseline. If one specific part matters, chart it on its own as a line.

If you use a stacked-area tool, keep the number of bands small and label them clearly. The current ToCharts tool overlays area series; it does not stack them or calculate their sum. Use another tool when you need a stacked total.

Making one

Paste a date column and one or more value columns into the line graph maker, then switch the chart type to area. The first column becomes equally spaced category labels; each other column becomes a series. Sort dates before pasting. This tool does not create a proportional time axis or preserve blanks as missing values. Try the same data as a line and as an area before you decide; check whether the filled version makes the intended comparison clearer or hides another series. Download PNG for slides or SVG for documents.

What this can't do yet

The current tool draws overlapping areas, not stacked areas, and does not calculate running totals. Its horizontal labels are equally spaced categories, even if dates have unequal intervals. Blank numeric cells become zero, so missing observations are not preserved as gaps. Each export is the chart rendered in the browser; there is no server-side batch chart generation API.