How to Make a Dual Axis Chart in Google Sheets

A dual axis chart is the perfect way to compare two different types of data on a single graph, especially when they have completely different scales. It lets you tell a richer story by visualizing the relationship between two metrics, like website traffic and conversion rate, without one distorting the other. This guide will walk you through exactly how to create a combo chart in Google Sheets, step-by-step, and share some practical examples of when this visual is most effective.

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What Exactly is a Dual Axis Chart?

A dual axis chart, often called a combo chart, is a single chart that features two different Y-axes: one on the left and one on the right. This setup is incredibly useful for plotting data series that are measured in different units or have wildly different magnitudes.

Imagine you want to compare your monthly advertising spend (measured in thousands of dollars) with the number of new sign-ups (measured in hundreds). If you plotted both on a single Y-axis, your sign-up data would look like a nearly flat line at the bottom, completely overshadowed by the much larger dollar values. The chart would be practically useless.

By creating a dual axis chart, you give each data series its own scale. Ad spend uses the left Y-axis (e.g., $0 to $50,000), while sign-ups use the right Y-axis (e.g., 0 to 500). Suddenly, you can see the relationship and trends in both metrics clearly, all within one chart.

When should you use a dual axis chart?

This type of chart is ideal for showing the relationship between two different kinds of values over the same period. Here are a few common scenarios:

• Sales Data: Comparing Total Revenue (in dollars) against the Number of Units Sold. You can see if selling more lower-priced items is affecting your total revenue.
• Marketing Analytics: Plotting Website Sessions (a large number) against Goal Conversion Rate (a percentage). This helps you answer questions like, "Did that big spike in traffic actually lead to more conversions?"
• Financial Performance: Showing a company's Stock Price (in dollars) versus its Trading Volume (number of shares).
• Product Management: Tracking Number of New Features Shipped versus Customer Support Tickets. Are new feature releases causing a spike in support inquiries?

In each case, you're looking for correlation and potential causation between two related but distinct metrics. A dual axis chart makes these connections instantly visible.

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Preparing Your Data for a Dual Axis Chart

Before you jump into making the chart, a little data preparation will make the process much smoother. Your data in Google Sheets should be organized in at least three columns:

1. Column A (The X-Axis): This column contains the labels for your horizontal axis. Typically, this is a time period like date, month, or quarter.
2. Column B (First Y-Axis Series): This column has the first set of numerical data you want to plot, which will correspond to the left Y-axis.
3. Column C (Second Y-Axis Series): This column has the second set of numerical data, which will become your right Y-axis.

Here’s an example for a marketing report comparing Website Sessions to Goal Conversion Rate for the first half of the year. Notice how the 'Sessions' are in the tens of thousands while the 'Conversion Rate' is a small percentage formatted as a number.

Example Data Structure:

Tip: For percentages like 'Conversion Rate', keep them formatted as decimals in your sheet (e.g., 2.5% is 0.025). You can format the axis to show as a percentage later in the chart settings.

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

Once your data is cleanly organized, creating the chart takes just a few clicks. Follow these steps.

Step 1: Select Your Data

Click and drag your mouse to highlight the entire range of data you want to include in the chart, including the column headers. In our example, you would select cells A1 through C7.

Step 2: Insert Chart

With your data selected, navigate to the top menu and click Insert > Chart. Google Sheets will automatically create a chart for you and open the Chart editor pane on the right side of your screen. It will probably guess incorrectly and make a standard line or column chart first, but don't worry, we'll fix that next.

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Step 3: Choose 'Combo chart' as the Chart Type

Google Sheets will plot both 'Website Sessions' and 'Conversion Rate' on the same axis, which looks wrong. 'Conversion Rate' will be a flat line near zero.

In the Chart editor pane, on the Setup tab, click the Chart type dropdown. Scroll down until you find the 'Combo chart' option and select it. This is Google Sheets' designated type for multi-axis charts.

Right away, the chart will adjust. It often defaults to making one series columns and another a line, which is usually what you want.

Step 4: Assign a Series to the Right Axis (The Key Step)

This is where the magic happens. Your chart now has two series, but they are both still using the left Y-axis. We need to assign one of them to its own axis on the right.

1. In the Chart editor, click on the Customize tab.
2. Find and click on the Series dropdown to expand its options.
3. Below this, you'll see another dropdown menu, typically set to 'Apply to all series'. Click this dropdown and select the data series you want to move to the right axis. In our example, this would be 'Conversion Rate', since its scale is so different.
4. Once you've selected your series, a new set of formatting options will appear just for that series. Look for the dropdown menu labeled 'Axis'.
5. Click it and change the selection from Left axis to Right axis.

Instantly, your chart will transform. A new vertical axis will appear on the right side of the chart with a scale appropriate for your second data series. The 'Conversion Rate' line will now be properly displayed against its own scale.

Step 5: Customize and Refine Your Chart

Your dual axis chart is now functional, but a few refinements can make it far more readable and professional.

• Give your axes titles: Still in the Customize tab, go to Chart & axis titles. Select 'Left vertical axis title' from the dropdown and type in a descriptive name, like "Website Sessions." Then do the same for the 'Right vertical axis title,' naming it "Conversion Rate (%)". Also, add a clear title to the overall chart.
• Adjust number formatting: Since our 'Conversion Rate' is on its own axis, let's make it look like a percentage. In the Customize tab, select Vertical axis. Use the 'Apply to axis' dropdown to select your Right axis. Scroll down to Number format and choose Percent.
• Change chart types for a series: In the Series section, you can change the visual representation. While a column/line combination is common, you could also use two lines or a column/area combo. Click the Type dropdown to see the options.
• Adjust colors and styles: Use the options within the Series section to change the line color, thickness, point shape, or column fill color to make your chart clearer and match your branding.

Dual Axis Chart: Common Mistakes to Avoid

While powerful, dual axis charts can be misleading if not used carefully. Keep these best practices in mind:

Avoid Cluttering the Chart

A dual axis chart works best with just two data series. While you can add three or four, the chart quickly becomes a tangled mess that is difficult for anyone to interpret. If you have more than two series to compare, consider splitting them into multiple charts.

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Label Everything Clearly

This is the most important rule. Without clear titles for the chart and both vertical axes, your audience won't know what they're looking at. The legend should also clearly explain what each line and column represents. Don't make people guess!

Use Contrasting Chart Types and Colors

Making one series a column chart and the other a line chart is an excellent way to visually separate them. Using distinct, easy-to-distinguish colors also makes the chart much easier to read at a glance. Avoid using two shades of blue, for example.

Correlation Isn't Causation

Just because two trends on your chart move together doesn't automatically mean one caused the other. Your revenue might go up at the same time you increased ad spend, but other factors could have been at play (like seasonality or a competitor's change in strategy). Your chart reveals a potential relationship, your job is to investigate it further.

Final Thoughts

Creating a dual axis chart in Google Sheets is a powerful way to show the relationship between two distinct data sets on a single, easy-to-read visual. By properly preparing your columns and using the 'Customize > Series' menu to assign an axis, you can transform a confusing graphic into a compelling story in just a few clicks.

Manually building these kinds of reports, especially when you're pulling data from different systems like Google Analytics and a paid ads platform, can be time-consuming and repetitive. We built Graphed to streamline that entire process. You can connect all your sources in seconds, then simply ask in plain English, "Show me last quarter's Facebook Ads spend vs. Shopify revenue on a combo chart," and get a live, interactive dashboard built for you instantly. This helps you focus more time on the insights behind the data, not on the chart setup itself.