How to Do Dual Axis in Tableau

Trying to compare two very different metrics, like overall sales revenue and the quantity of items sold, on a single graph can feel like an impossible task. If you plot them on the same axis, the measure with the larger scale completely flattens the other, making your visualization useless. This is exactly where Tableau's dual-axis chart comes in. This guide will walk you through exactly how and when to use this powerful feature to tell a richer story with your data.

What is a Dual-Axis Chart?

A dual-axis chart is a visualization that combines two different measures on a single chart using two separate axes. It typically has a shared X-axis (often representing time or a category) and two independent Y-axes - one on the left and one on the right. Each Y-axis represents the scale for one of the measures you're analyzing.

Think of it as laying two charts on top of each other. You might have a bar chart showing sales figures using the left Y-axis and, layered on top, a line chart showing profit ratio using the right Y-axis. This allows you to spot relationships and correlations between measures that would be impossible to see otherwise.

Why Use a Dual-Axis Chart in Tableau?

This feature isn't just about making your dashboards look more complex, it serves very practical purposes that help you get clearer insights. There are two primary reasons why you would create a dual-axis chart.

1. Comparing Measures with Wildly Different Scales

This is the most common use case. Imagine you want to track your monthly sales revenue (which is in the millions of dollars) alongside your customer traffic count for the same period. If you put both on a single axis, your sales line would soar to the top of the chart, while your traffic line would look like a completely flat line near zero, even if it's fluctuating by tens of thousands of visitors.

By creating a dual-axis chart, you assign 'Sales' to the left axis (scaled in millions) and 'Customer Traffic' to the right axis (scaled in thousands). Both lines will now be fully visible and plotted according to their own independent scales, allowing you to clearly see how shifts in traffic might be related to changes in sales revenue.

• Example: Compare Website Sessions (e.g., 50,000) vs. Conversion Rate (e.g., 2.5%).
• Example: Track Total Revenue ($) vs. Quantity of Products Sold.

2. Comparing Measures Using Different Chart Types (Combination Charts)

The second major benefit is the ability to create combination charts. In Tableau, once you create a dual-axis chart, you get a separate Marks card for each measure. This means you can represent one measure as a bar and the other as a line, dot, or shape.

This technique is fantastic for showing the relationship between a magnitude and a rate. For instance, you could plot your sales volume for different product categories as bars, while overlaying a line that shows the profit margin for each category. This can instantly reveal which high-volume categories are also your most profitable - and which ones might be selling a lot but aren't actually contributing much to your bottom line.

How to Create a Dual Axis Chart in Tableau: A Step-by-Step Guide

Let’s walk through building a classic combination chart that visualizes monthly Sales (as a bar chart) and Profit (as a line chart) over time. This will help us understand both sales volume and profitability in one view.

Step 1: Build Your Initial Chart

First, you need a basic chart with one measure. This will be the foundation for our dual-axis chart.

1. Connect to your data source in Tableau (we’ll use the Sample - Superstore dataset that comes with Tableau for this example).
2. Drag the Order Date dimension to the Columns shelf. Right-click the pill and choose the continuous "Month" a second time (the one with the green calendar icon) to get a monthly trend.
3. Drag the Sales measure to the Rows shelf.

At this point, you'll have a simple line chart showing total sales over time.

Step 2: Add Your Second Measure

Now, let's bring in the second piece of our analysis. Drag the Profit measure from the Data pane and drop it onto the Rows shelf, to the right of the existing 'SUM(Sales)' pill.

You'll now see two separate line charts stacked on top of each other, one for sales and one for profit. Tableau has created two rows in the view, each with its own chart and axis.

Step 3: Enable the Dual Axis

This is where the magic happens. To combine these two separate charts into one, you need to enable the dual-axis functionality.

Find the second pill on your Rows shelf (in this case, SUM(Profit)), right-click on it, and select Dual Axis from the dropdown menu.

Immediately, your two charts will merge into a single space. You will now see your Sales and Profit lines plotted in the same chart area, with one axis on the left (for Sales) and a new one on the right (for Profit).

Step 4: Customize Your Mark Types

By default, both measures are likely displayed as lines. To make this a more effective combination chart, let’s change the mark type for each measure independently.

1. Look at your Marks card. You should now see three tabs: "All," "SUM(Sales)," and "SUM(Profit)." This allows you to control the appearance of each measure separately.
2. Click on the SUM(Sales) Marks card. In the dropdown menu that says "Automatic," select Bar. Your sales data will now appear as a bar chart.
3. Click on the SUM(Profit) Marks card. You can leave this as a Line, or change it back if needed. Try customizing the color or thickness of the line to make it stand out.

Step 5: Adjust and Format Your Chart

Your chart is functional, but a little formatting goes a long way. Let's clean it up so it's easy to read.

• Colors: On each measure's Marks card, click "Color" to choose distinct, easy-to-read colors. For example, make the sales bars a soft gray and the profit line a bold blue or orange.
• Bar Size: On the "SUM(Sales)" Marks card, click on "Size" and adjust the slider to make the bars a bit thicker or thinner for better visual appeal.
• Axis Titles: Right-click on each axis (left and right) and select "Edit Axis." You can then change the title to be more descriptive, like "Total Sales (USD)" or "Total Profit (USD)."

Important Note: When to Synchronize Axes

In some cases, you might want both axes to share the exact same scale. This is only appropriate when you are comparing two measures that have the same unit and a similar magnitude (e.g., Sales vs. Sales Target, or a count of Men vs. a count of Women).

To do this, simply right-click on either of the axes and select Synchronize Axis. Be careful! If you synchronize axes for measures with different scales (like our Sales vs. Profit example), you’ll end up flattening one of your lines again, defeating the purpose of the dual-axis chart in the first place.

Common Mistakes and Quick Fixes

Dual-axis charts are powerful, but it’s easy to make a few common mistakes along the way. Here’s what to look out for.

Problem: My chart is too crowded and hard to read.

Solution: A dual-axis chart is already information-dense. Adding too much more, like a third measure represented by 'Size', can create a visual mess. For clarity, stick to two measures. Try to use complementary mark types - bars for volume and lines for trends often work well together. If it's still confusing, consider placing two separate charts side-by-side on your dashboard instead.

Problem: Viewers are confusing the left and right axes.

Solution: Color-coding is your best friend here. Make sure the color of the bar or line clearly matches up with its corresponding axis title. For example, if your Profit line is blue, you can go into the axis formatting options and make the font color for the Profit axis title blue as well. This small visual cue helps connect the data series to its scale instantly.

Problem: I don't see separate Marks cards for each measure.

Solution: You will only see separate Marks cards after you have enabled the dual-axis feature. If you only see one Marks card after you've placed two measures on the Rows/Columns shelf, it means they haven't been combined yet. Go back to Step 3 and make sure you've selected "Dual Axis" by right-clicking the second measure pill.

Final Thoughts

Mastering the dual-axis chart in Tableau opens a new level of data storytelling, allowing you to compare different measures in a single, insightful view. By combining mark types and leveraging independent scales, you can uncover relationships in your data that would otherwise stay hidden.

Of course, becoming proficient in tools like Tableau takes time, and sometimes you just need a quick answer without getting bogged down in configuration. That's why we built Graphed. Instead of clicking and dragging pills, you can just ask in plain English, "create a chart comparing my monthly sales and profit as bars and a line," and get a live, interactive visualization in seconds. Our goal is to automate the busy work so you can spend less time building charts and more time acting on the insights they provide.