Area Chart
A line chart with the space below filled in, emphasizing the volume or magnitude of change over time. When stacked, area charts reveal how individual parts contribute to a whole.
// 01 — The chart
What it looks like
An area chart showing monthly revenue growth. The filled area below the line emphasizes the cumulative volume of revenue over time.
// 02 — Definition
What is an area chart?
An area chart is essentially a line chart with the region between the line and the X-axis filled in with color or a gradient. This simple addition shifts the visual emphasis from the trend (what a line chart shows best) to the volume or magnitude of the values over time.
The filled area creates a sense of accumulated quantity. While a line chart answers “How did the value change?”, an area chart answers “How much was there?” This makes area charts especially effective for revenue, traffic, inventory levels, and other metrics where total volume matters as much as the trend.
When multiple series are stacked on top of each other, area charts become one of the best ways to show how individual components contribute to a whole over time — something a line chart alone cannot do.
Origin: The area chart was invented by William Playfair in 1786, appearing in the same Commercial and Political Atlas that introduced the bar chart. Playfair used filled areas to show England’s imports and exports over time, creating what may be the first time-series area chart in history.
// 03 — Anatomy
Parts of an area chart
// 04 — Usage
When to use it — and when not to
- You want to emphasize the magnitude or volume of a value over time, not just the trend
- Showing how a total is divided into parts over time (stacked area chart)
- Displaying cumulative totals like revenue, page views, or inventory levels
- You have a single data series and want a more visually impactful version of a line chart
- Comparing the overall volume between two periods or scenarios
- Your audience cares about “how much” as much as “how it changed”
- You have multiple overlapping series — filled areas will obscure each other
- Precise value reading is critical — the fill makes it harder to read exact values than a line chart
- You only care about the trend direction, not the volume — use a line chart
- Your data is categorical rather than continuous over time — use a bar chart
- You have many series (5+) — stacked areas become unreadable with too many layers
- The Y-axis doesn’t start at zero — the filled area will misrepresent the volume
// 05 — Reading guide
How to read an area chart
Follow these steps whenever you encounter an area chart.
Read the title and axes
What metric is being shown? What’s the time range? The Y-axis tells you the scale and units. Without this context, you can’t interpret the chart accurately.
Follow the trend line
The upper edge of the filled area is a line chart. Read it the same way — is the trend rising, falling, flat, or cyclical? Ignore the fill for now and just focus on the shape of the line.
Assess the volume
Now look at the filled area. A large filled region means high cumulative values; a thin sliver means low values. The visual “weight” of the fill is what makes area charts powerful for conveying magnitude.
For stacked areas, read the layers
In a stacked area chart, each colored layer represents a different category. The thickness of each layer at any point shows that category’s value. The top line shows the total. Read individual layers by their thickness, not their vertical position.
Check the baseline
An area chart’s visual impact depends on the Y-axis starting at zero. If it doesn’t, the filled area will exaggerate differences and misrepresent the volume. Always verify the baseline.
// 06 — Common mistakes
Mistakes to watch out for
Overlapping areas without transparency
When multiple area series overlap, opaque fills hide the data beneath. Always use semi-transparent fills or consider a stacked area chart instead. Alternatively, switch to a line chart if overlap is unavoidable.
Using area charts when a line chart would be better
If the only thing that matters is the trend direction, the filled area adds visual clutter without value. Area charts are specifically for when volume or magnitude matters — if it doesn’t, use a simpler line chart.
Not starting the Y-axis at zero
The filled area is the chart’s primary visual encoding. If the Y-axis is truncated, the area will dramatically exaggerate small differences, making minor fluctuations look like massive swings.
Too many stacked layers
With more than 4–5 stacked areas, the bottom layers become impossible to read because they’re not anchored to the baseline. The eye can’t accurately compare non-baseline-aligned bands. Consider small multiples instead.
Stacking series that shouldn’t be summed
Stacked area charts imply that the layers add up to a meaningful total. If the series are independent (e.g., temperatures of different cities), stacking them creates a nonsensical total. Use overlapping lines instead.
// 07 — Real-world examples
Where you’ll see area charts used
Finance: Portfolio value over time
Investment platforms like Robinhood and Fidelity use area charts to show your portfolio’s total value over time. The filled area makes the accumulated wealth feel tangible — a rising, thickening area feels like growth, while a collapsing area feels like loss.
FinanceWeb analytics: Traffic by source
Google Analytics uses stacked area charts to show website traffic broken down by source (organic, direct, referral, social). The total height shows overall traffic, while each layer reveals which channels are growing or shrinking over time.
AnalyticsEnergy: Electricity generation by source
Grid operators and energy dashboards use stacked area charts to show how much electricity comes from coal, gas, nuclear, wind, and solar throughout the day. The chart reveals how the energy mix shifts as demand rises and falls.
Energy// 08 — At a glance
Quick reference
// 09 — Variations
Types of area charts
The basic area chart has several powerful variants for different analytical needs.
Stacked area chart
Layers areas on top of each other to show how components contribute to a total over time.
100% stacked area
Normalizes each time point to 100%, showing how proportions shift over time rather than absolute values.
Streamgraph
Layers flow around a central axis instead of a baseline. Creates an organic, river-like visualization of changing composition.
Ridgeline / joy plot
Overlapping area charts arranged vertically. Great for comparing distributions or trends across many groups.
// 10 — FAQs
Frequently asked questions
What is an area chart?+
An area chart is essentially a line chart with the region between the line and the X-axis filled in with color or a gradient. This simple addition shifts the visual emphasis from the trend (what a line chart shows best) to the volume or magnitude of the values over time.
When should you use an area chart?+
Use an area chart when you want to emphasize the magnitude or volume of a value over time, not just the trend. It also works well when showing how a total is divided into parts over time (stacked area chart), and when displaying cumulative totals like revenue, page views, or inventory levels.
When should you avoid an area chart?+
Avoid an area chart when you have multiple overlapping series — filled areas will obscure each other. It is also a poor fit when precise value reading is critical — the fill makes it harder to read exact values than a line chart, or when you only care about the trend direction, not the volume — use a line chart.
How is an area chart different from a line graph?+
Both an area chart and a line graph can look similar at first glance, but they answer different questions. Reach for an area chart when the comparisons and patterns it was designed to reveal match what you need to communicate, and choose a line graph when its particular strengths better fit your data and audience.
Is an area chart suitable for dashboards?+
Yes — an area chart can work well in dashboards as long as the panel is large enough for readers to perceive the encoded values, has a clear title, and includes the legend or axis labels needed to interpret it.
What category of chart is an area chart?+
Area Chart belongs to the Time Series family of charts. Charts in that family are designed to answer the same kind of question, so they often work as alternatives when one doesn't quite fit your data.