Stacked Area Chart

Overview

A stacked area chart layers multiple data series on top of each other, so the top edge shows the total while each band reveals its individual contribution. Use it when your audience needs to see both "how much total?" and "what is each part's share?" in one view.

When to use

• Show composition and how parts contribute to a whole over time
• Display cumulative totals across product lines, regions, or categories
• Emphasize both individual growth and aggregate trends simultaneously
• Compare relative proportions as they shift period to period
• Communicate budget allocation, resource distribution, or market share

Not ideal

• When individual series values matter more than composition (use separate lines)
• Comparing exact values of middle or top series (they sit on a moving baseline)
• More than 5–7 series (visual clutter makes the chart unreadable)
• When negative values exist (stacking breaks down)

Key variations

• Standard stacking: Raw values stacked, top edge = total
• Percentage stacking: Normalized to 100%, shows share shifts regardless of total
• Stream graph: Centered baseline for aesthetic/narrative emphasis
• With or without smoothing
• Gradient fills for visual polish

Use cases

• Product management: Revenue breakdown by product line over quarters
• Marketing: Traffic sources (organic, paid, social, direct) over months
• Finance: Portfolio allocation across asset classes over years
• Energy: Power generation mix (solar, wind, coal, gas) over time
• HR/Operations: Headcount by department or team across growth periods
• E-commerce: Order volume by product category per week
• Government: Budget spending by ministry or department across fiscal years

Quick setup in Line Graph Maker

1. Prepare CSV with columns: x (time/category), y (value), series (category name).
2. Upload or paste data into the editor.
3. Select "Stacked Area" as chart type.
4. Adjust areaOpacity (0.6–0.8 works well for stacked charts).
5. Reorder series in the legend to control stacking order (most stable at bottom).
6. Export or share your chart.

Data (CSV)

x,y,series
2025-01-01,30,Product A
2025-01-02,35,Product A
2025-01-03,40,Product A
2025-01-04,38,Product A
2025-01-05,42,Product A
2025-01-06,45,Product A
2025-01-07,48,Product A
2025-01-01,25,Product B
2025-01-02,28,Product B
2025-01-03,32,Product B
2025-01-04,30,Product B
2025-01-05,35,Product B
2025-01-06,38,Product B
2025-01-07,40,Product B
2025-01-01,15,Product C
2025-01-02,18,Product C
2025-01-03,20,Product C
2025-01-04,22,Product C
2025-01-05,25,Product C
2025-01-06,28,Product C
2025-01-07,30,Product C

Performance tips

• Limit to 5–7 series for readability; merge smaller categories into "Other"
• Use consistent color schemes so audiences learn the palette across reports
• Enable interactive tooltips — they are essential because middle series are hard to read visually
• For percentage stacking, clearly label the Y-axis as "% of total"

FAQ

How do I read the value of a middle series? Look at the vertical distance between that series' top edge and its bottom edge at a given X position. Interactive tooltips make this much easier — hover to see exact values without mental math.

Stacked area vs stacked bar — which should I choose? Use stacked area when time is the X-axis and you want to show continuous flow. Use stacked bar when comparing discrete categories or when exact values per segment matter more than trend.

When should I use percentage stacking instead of raw values? Use percentage (100%) stacking when share shifts are more important than absolute growth. For example: "Did Product A's share grow from 30% to 45%?" vs "Did total revenue grow from $100K to $200K?" If both matter, show two charts.

What order should I stack the series? Place the most stable or most important series at the bottom (closest to the baseline), because it is the easiest to read. Put volatile or "other" categories near the top where visual distortion from the moving baseline is less noticeable.

Can I highlight a single series in a stacked area chart? Yes. Use the emphasis option to dim other series on hover, making the selected series stand out. Alternatively, use a different opacity or color saturation for the highlighted series.

How do I handle missing data in one series? Stacking requires all series to have values at every X point. Fill missing values with zero (if the series genuinely had no contribution) or interpolate. Document your approach to avoid misleading the audience.

What is a stream graph, and when should I use it? A stream graph is a stacked area with the baseline centered rather than anchored at zero. It creates a symmetric, flowing shape that looks visually striking in presentations. Use it for narrative storytelling; avoid it for analytical dashboards where precise reading matters.