How to Make a Dual Axis Chart in Excel

Ever tried to show your massive website traffic numbers alongside your tiny conversion rate on the same graph? It can be frustrating - one dataset is so large it flattens the other, making it impossible to see the relationship between them. This is where a dual-axis chart in Excel comes in. This article will walk you through exactly what a dual-axis chart is, when to use one, and the step-by-step process to build your own.

What is a Dual-Axis Chart?

A dual-axis chart, sometimes called a combo chart, is a single chart that displays two different types of data by using two different Y-axes (the vertical ones). You have a primary Y-axis on the left and a secondary Y-axis on the right, while both data series share the same X-axis (the horizontal one) across the bottom.

Think of it like telling two related stories at the same time. Let's say you want to see if your increased marketing ad spend is leading to more sales. Your ad spend might be in the tens of thousands of dollars, while your number of sales is in the hundreds. If you plot these on a standard chart with one Y-axis, the sales numbers will look like a flat line at the bottom, completely dwarfed by the ad spend. You won't be able to spot any trends or correlations.

A dual-axis chart solves this. It lets you plot Ad Spend on the left axis (from $0 to $50,000) and the Number of Sales on the right axis (from 0 to 500). Suddenly, you can see how the two lines move together (or don't) over time, giving you a much clearer picture of your performance.

When to Use a Dual-Axis Chart

Dual-axis charts are fantastic tools, but they should be used with a specific purpose in mind. They’re not just for cramming more data onto a single graph. They shine brightest when you need to show the relationship between two variables that are otherwise difficult to compare.

Here are a few common scenarios where a dual-axis chart is the perfect choice:

• Comparing data with different scales. This is the classic use case. For example, comparing marketing ad spend (e.g., $100,000) with the click-through rate (e.g., 2.5%). Without a second axis, the CTR percentage would be invisible.
• Comparing data with different units. You can visualize the relationship between two distinct metrics, like the number of units sold (a whole number) and the revenue generated (a dollar amount). Another great example is plotting total website sessions against the site's average load time in seconds.
• Showing correlation between two metrics. Dual-axis charts make it easy to see if a change in one metric corresponds with a change in another. For instance, does a spike in rainfall (measured in inches) lead to an increase in umbrella sales (measured in units)? A combo chart can make that relationship visually obvious.

A Word of Caution: Common Pitfalls

Before we build one, it's worth noting a couple of pitfalls. The biggest risk with a dual-axis chart is implying a relationship between two metrics that doesn't actually exist. Just because two lines on a chart trend in the same direction doesn't automatically mean one caused the other. Always apply critical thinking to the story your chart is telling.

Another common mistake is making the chart too busy. A dual-axis chart works best with just two data series (like one set of columns and one line). Trying to add a third or fourth data series and more axes can create a "spaghetti chart" that’s confusing and impossible to read. The goal is clarity, not complexity.

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

Ready to build one? Let's walk through an example. Imagine we run a small e-commerce store and want to see the relationship between our monthly ad spend and the number of new customers we've acquired.

Step 1: Set Up Your Data

First, make sure your data is organized in a clear, simple table in Excel. The best layout is to have your shared time period (like months or days) in the first column, followed by the two data series you want to compare in the next two columns.

For our example, the table looks like this:

This simple structure is easy for Excel to understand and turn into a chart.

Step 2: Insert a Basic Chart

We'll start by creating a standard chart. Don't worry about the dual-axis part just yet.

1. Highlight the entire data table, including the headers (from "Month" down to "175").
2. Navigate to the Insert tab on the Excel ribbon.
3. In the Charts section, click on Recommended Charts. Excel is pretty smart and will often suggest a good starting point. A simple "Clustered Column" chart is a perfect place to start. Select it and click OK.

You’ll now have a basic column chart. You'll immediately notice the problem we discussed earlier: the "Ad Spend" columns are huge, while the "New Customers" columns are so small they're barely visible. Let's fix that.

Step 3: Create the "Combo" Chart

Modern versions of Excel have made creating a dual-axis chart incredibly straightforward with the "Combo" chart type. This is the easiest and most effective method.

1. Right-click anywhere in the chart area and select Change Chart Type... from the dropdown menu.
2. This opens the "Change Chart Type" window. In the list on the left, select Combo, which is usually at the very bottom.
3. You will now see a preview of your chart with options for each data series ("Ad Spend" and "New Customers"). This is where the magic happens.
4. You'll see the chart preview update instantly, showing the columns and line with two different vertical axes. Click OK.

And that's it! You have successfully created a dual-axis chart. Now let's make it look professional and easy to understand.

Step 4: Customize and Format Your Chart for Clarity

A good chart tells a clear story without needing a long explanation. Here are a few essential cleanup steps to make your dual-axis chart publication-ready.

Add a Chart Title

Your chart needs a descriptive title. By default, it might say something generic like "Chart Title." Click on it and change it to something that explains what the viewer is seeing, like "Monthly Ad Spend vs. New Customer Acquisition."

Label Your Axes

This is the most important step for a dual-axis chart. Without clearly labeled axes, your audience won't know which data series corresponds to which scale.

1. Make sure your chart is selected. Click the green + button that appears on the right side of the chart (this is the Chart Elements button).
2. Check the box for Axis Titles. You will now see text boxes appear next to each of your three axes.
3. Click on each axis title box to edit the text:

Tweak Colors and Your Legend

Excel automatically includes a legend to tell you which color represents which data. Make sure it's clear. A legend at the top or bottom of the chart is usually best. If you don’t like the default colors, you can right-click on any data series (the columns or the line) and select Format Data Series... to change the color and style.

After these formatting cleanups, you'll have a professional-looking, easy-to-read dual-axis chart that clearly shows the relationship between two different, but related, sets of business data.

Final Thoughts

Creating a dual-axis chart in Excel is a powerful way to visualize complex relationships in your data. By plotting two different metrics on separate vertical axes, you can uncover trends and correlations that would be impossible to see in a standard chart, allowing you to tell a richer, more insightful story about your business performance.

While building these charts in Excel is completely doable, we know it can be part of a time-consuming weekly or monthly reporting cycle: download the CSVs, clean the data, create the pivot tables, and build the charts, over and over again. We built Graphed because we wanted to automate this entire process. Instead of manually wrestling with spreadsheets, you can connect your data sources (like Google Analytics, your ad platforms, and your CRM) one time and then create dashboards using simple, natural language. Asking "show me monthly ad spend vs. new customers as a combo chart" generates a live, interactive visualization instantly, giving you back hours to focus on strategy, not spreadsheet formatting.