How to Combine Two Bar Charts in Tableau

Combining two bar charts into one is a simple yet powerful way to compare different data sets at a glance. Whether you want to see sales versus profit or this year's performance against last year's goals, creating a combo chart in Tableau allows for richer, more contextual data storytelling. This tutorial will walk you through the primary methods for combining bar charts in Tableau, guiding you step-by-step with practical examples.

Why Bother Combining Bar Charts?

Before getting into the "how," let's quickly touch on the "why." A single bar chart is great for showing the magnitude of a single measure across different categories. But what happens when you want to compare that measure to something else? You could create two separate charts and place them side-by-side on a dashboard, but that consumes valuable space and makes direct comparisons more difficult for your audience.

By bringing both data series onto the same visualization, you can highlight relationships and discrepancies more effectively. This technique is useful for:

• Comparing two different measures: For example, comparing the Sales for each product category with the Profit it generated.
• Measuring actuals against a target: Visualizing actual Revenue alongside your Revenue Goal for each sales rep.
• Analyzing trends over time: Showing 2023 Sales versus 2024 Sales by month.

Now, let's build some charts.

Method 1: The Dual-Axis Bar Chart

The dual-axis chart is one of the most common ways to combine two bar charts. It works by layering two charts on top of each other, each with its own axis. This is perfect for when you are comparing two measures that have different scales, like “Number of Units Sold” (which might be in the thousands) and “Profit” (which might be in the dollars).

Let's say you want to compare Sales and Profit Ratio for each Sub-Category using Tableau's Sample Superstore dataset.

Step-by-Step Instructions:

1. Create Your First Bar Chart: Start by dragging the Sub-Category dimension to the Columns shelf and the Sales measure to the Rows shelf. You'll have a standard vertical bar chart.
2. Add the Second Measure: Drag your second measure, Profit Ratio, and drop it onto the Rows shelf, to the right of the Sales pill.
3. Create the Dual Axis: At this point, you'll have two separate bar charts, one above the other. To combine them, right-click on the Profit Ratio pill in the Rows shelf and select Dual Axis from the dropdown menu.

Your charts are now layered on top of each other. But they probably don't look right yet — Tableau might have turned one or both of them into a different chart type, like circles or lines.

1. Adjust the Marks card: In the Marks card area, you’ll now see tabs for "All," "SUM(Sales)," and "AVG(Profit Ratio)." This allows you to control the appearance of each chart independently.

Click on the "SUM(Sales)" mark tab and change the chart type to Bar. Then, click on the "AVG(Profit Ratio)" tab and also change its type to Bar.

1. Refine the View: The chart is functional but messy. To improve readability, you can make one set of bars thinner than the other. On the Marks card for your "SUM(Sales)" chart, click on the Size button and move the slider to the left to make those bars thinner. This creates a really nice effect where one bar sits neatly inside the other.
2. Synchronize the Axes (Important!): Look at the two Y-axes on either side of your chart. They likely have different scales, which can be highly misleading. To fix this, right-click on the secondary axis (the one on the right) and select Synchronize Axis. This makes sure that a value on one axis lines up with the same value on the other, creating a true comparison. If your measures have drastically different scales (e.g., Sales in millions and Profit Ratio as a percentage), a dual-axis chart might not be the best choice. Synchronizing works best when the measures are reasonably comparable.

Method 2: Side-by-Side Bar Charts

What if you don't want to overlay the bars, but rather place them next to each other for each category? The side-by-side bar chart (also known as a shared axis or grouped bar chart) is perfect for this. It’s ideal for comparing two measures with a similar scale, as they will share a single axis.

Let's build a side-by-side chart comparing Sales and Profit across different Regions.

Step-by-Step Instructions:

1. Start Your Chart: Drag the Region dimension to the Columns shelf and the Sales measure to the Rows shelf.
2. Add the Second Measure to the Y-Axis: Now, drag your second measure, Profit, and hover it over the existing Y-axis of your Sales chart (the vertical axis). You'll see a light green, double-ruler icon appear. Drop the Profit pill there.
3. Tableau Works Its Magic: Tableau will automatically create a side-by-side bar chart. Check your shelves — you'll notice that Tableau has done a few things:
4. Customize Your Chart: From here, you can format the chart as needed. Drag the Color Legend to reorder colors, or edit the colors to match your brand. You can also drag additional measures onto the Measure Values card to include them as new bars in each group.

Method 3: Creating a Stacked Bar Chart

A third way to "combine" your data is with a stacked bar chart. This method is best when you want to show the composition of a total. Instead of seeing bars next to each other, one bar is stacked on top of the other. It helps answer questions like, "What is our total revenue, and how much of it came from each product line?"

Let's use the same setup as before: comparing Sales and Profit across Regions.

Step-by-Step Instructions:

1. Start with the Side-by-Side Setup: Follow the first two steps from the side-by-side bar chart method above. You should have Region and Measure Names on Columns, and Measure Values on Rows. You'll see a side-by-side chart.
2. Move 'Measure Names' to Color: The only change you need to make is to move the Measure Names pill from the Columns shelf to the Color tile on the Marks Card.

That's it! Tableau immediately restacks the bars. The total height of each bar now represents the combined sum of the measures inside (Sales + Profit), with colors showing the contribution of each.

1. Add Labels for Clarity: It can be hard to read the exact values in a stacked chart. Drag the Measure Values pill to the Label tile on the Marks Card. This will display the totals for each colored segment so your audience can see the numbers without hovering.

Tips for Making Your Combined Charts Effective

• Choose the Right Method: Use shared-axis (side-by-side) charts for direct "apples-to-apples" comparisons. Use dual-axis charts cautiously, especially when scales differ, and use it smartly by making one bar thinner than the other to show actual vs target. Use stacked charts for showing part-to-whole relationships.
• Be Careful with Sizing: In a dual-axis chart where you want an overlaid effect, make sure the "foreground" bar is thinner than the background bar.
• Don't Forget Labels: When bars are layered or stacked, it's hard to read exact values. Use labels strategically to call out the most important numbers.
• Use Color Thoughtfully: Use distinct but complementary colors. Don't rely on color alone to convey meaning — make sure your labels and tooltips are descriptive.

Final Thoughts

Mastering these three methods - dual-axis, side-by-side, and stacked bars - will significantly expand your data visualization capabilities in Tableau. Each technique offers a unique way to compare measures, allowing you to build dashboards that are not only informative but also intuitive and easy to understand.

Of course, sometimes you need answers without getting caught up in wrestling with shelves, marks cards, and axis settings. For moments like those, we built Graphed. Our platform is designed to take the manual work out of reporting by letting you ask for charts in sentences instead of clicks. Just connect your data sources, and you can simply type, "Show me a side-by-side bar chart of sales vs profit by region last quarter," and get an interactive chart instantly, letting you focus on the insights, not the setup.