When to Use Area Charts: Making the Most of Visualizing Trends Over Time

Introduction

In the vast world of data visualization, choosing the right chart type can significantly enhance the way your audience understands your data. Area charts are often overlooked, but they’re a fantastic choice when you want to show how individual components contribute to a whole over time. If you’ve ever wondered whether to use a line chart or something more, the area chart might be your answer.

An area chart is like a line chart with a little more oomph—providing a way to visualize not only trends over time but also the cumulative effect of those trends. In this post, we’ll break down the key moments when an area chart is your best option, how to use it effectively, and the potential pitfalls to avoid.

What is an Area Chart?

An area chart is similar to a line chart, with the space between the line and the axis filled with color or shading. This shading helps emphasize the magnitude of the data points, highlighting how values contribute to a cumulative total over time.

The key strength of an area chart is that it can show the development of different categories relative to each other, while also allowing viewers to understand the total sum of those categories.

When Should You Use an Area Chart?

Area charts are powerful tools, but like any chart type, they work best in certain scenarios. Here are the key situations where an area chart is the perfect choice:

1. Visualizing Changes Over Time

The primary use case for an area chart is when you want to show how data evolves over time. Like line charts, area charts are time-series charts that help audiences easily see the rise and fall of values across a set period.

However, the added benefit of an area chart is that it highlights the volume or magnitude of the data. The filled area helps show not just the trend but the total impact of those values over time.

Example: If you’re tracking website traffic from different sources (organic, social media, paid ads), an area chart can show how the total number of visitors has grown while also breaking down where those visitors came from.

2. Showing Parts of a Whole Over Time

If you want to show how different categories contribute to a total value over time, a stacked area chart is a great option. Each layer of the chart represents a different category, and the thickness of each layer reflects its contribution to the total.

Example: In a sales report, you could use a stacked area chart to show how different product categories (e.g., electronics, furniture, apparel) contribute to total revenue over time. This gives a clear view of both the overall trend and the importance of each category.

3. Comparing the Total Volume

When the total value is just as important as individual trends, an area chart can help. The filled area gives a sense of cumulative impact, which can be useful when comparing growth or total volume between different datasets.

Example: Comparing energy consumption across multiple sources (solar, wind, coal) over time. An area chart can show both the increase in overall energy usage and how each source contributes to the total.

4. Emphasizing Magnitude

Area charts provide a way to emphasize the size or magnitude of changes over time. If you want to draw attention to the volume of data rather than just the direction of trends, an area chart offers a more impactful way to do that than a simple line chart.

Example: Showing the increase in monthly subscriptions to a service, where the height and fullness of the chart emphasize the growing subscriber base.

Types of Area Charts

There are two main types of area charts, each suited to different kinds of data and storytelling needs.

1. Simple Area Chart

A simple area chart is the most basic form and is similar to a line chart but with the area under the line filled in. It’s great for showing trends over time, but it only represents one data series.

When to use it: Use a simple area chart when you want to show the magnitude of a single trend, such as revenue growth, website traffic, or product sales over time.

2. Stacked Area Chart

A stacked area chart displays multiple datasets, with each series “stacked” on top of the other. This chart type is particularly useful when you want to see how different categories contribute to a whole over time.

When to use it: Use a stacked area chart when you need to show the contribution of different categories to the total, such as market share by product or service lines over time.

How to Effectively Use Area Charts

To make the most of your area charts, it’s essential to follow a few best practices:

1. Use Transparent Colors

Because area charts involve overlapping layers (especially in the case of stacked area charts), it’s important to use transparent or light colors. This helps your audience see all the layers clearly and prevents one data series from visually dominating the others.

2. Limit the Number of Categories

While stacked area charts can handle multiple datasets, too many categories can make the chart cluttered and difficult to interpret. Try to limit the number of categories to three to five to maintain clarity.

3. Ensure the Data Adds Up

One of the risks of using a stacked area chart is that it can be easy to misinterpret the total if the data isn’t properly formatted. Make sure the total value is clear, and the audience can easily see how individual parts contribute to that total.

4. Choose the Right Scale

Pay close attention to your chart’s scale. If the differences between data points are too small, they might not be visible. Conversely, if the scale is too large, the changes might seem insignificant, even if they’re not.

5. Focus on the Big Picture

The power of an area chart lies in its ability to show cumulative trends over time. Don’t get bogged down in minor fluctuations; instead, focus on the big picture and emphasize the overall trends and totals.

Examples of Area Charts in Action

1. Website Traffic Sources

Imagine you want to track how website traffic has grown over the past year, with different sources such as organic search, social media, and paid ads contributing to the total. A stacked area chart can visually break down how much traffic each source has provided, while also showing the total traffic growth.

2. Revenue by Product Line

Let’s say your business sells multiple product lines, and you want to see how each one contributes to total revenue. A stacked area chart allows you to visualize both the overall revenue growth and the contribution of each product line.

3. Energy Consumption

For a utility company tracking energy consumption from different sources (like wind, solar, and fossil fuels), an area chart provides an excellent way to show how each source contributes to the overall energy supply and how this changes over time.

Common Mistakes to Avoid with Area Charts

Like any chart type, area charts can be misused or misunderstood if not applied correctly. Here are some common mistakes to avoid:

1. Using Too Many Categories

Stacking too many categories on top of each other can make the chart unreadable. Stick to three to five categories to maintain clarity.

2. Ignoring Cumulative Data

Area charts are meant for cumulative data, not for datasets that don’t build on each other. Avoid using them for isolated data points, as it will make the chart confusing.

3. Misrepresenting Data

Be careful not to skew the perception of your data. Ensure that the vertical axis starts at zero to avoid exaggerating minor differences in trends.

Conclusion

Area charts are a fantastic tool when used correctly, offering a clear and impactful way to show trends and the cumulative impact of those trends over time. Whether you’re tracking website traffic, sales, or resource consumption, area charts allow you to show not just the growth or decline of data points but also how different categories contribute to a whole.

By focusing on the right use cases—such as cumulative data over time—and following best practices like using transparent colors and limiting categories, you can create area charts that enhance your data storytelling.