How to Add an Additional Axis in Excel Graph
When you're trying to visualize two different types of data on a single Excel chart, things can get messy. If one dataset's scale massively overshadows the other - like plotting revenue in the millions against a customer satisfaction score from 1-10 - one of your data series ends up looking like a flat line at the bottom. This article will show you exactly how to solve this by adding a secondary axis to your Excel graph, allowing you to clearly compare different data series in one cohesive chart.
When and Why to Use a Secondary Axis in Excel
A secondary axis (also known as a second Y-axis) is a vertical axis added to the right side of your chart, opposite the primary vertical axis on the left. It's a lifesaver in a few common scenarios where a single axis just won't cut it.
1. Comparing Data with Different Scales
This is the most frequent reason to use a secondary axis. Imagine you're a marketing manager tracking monthly website traffic (in the hundreds of thousands) and the number of blog posts published (fewer than 20 per month). If you plot both on the same axis, the blog post data will be completely flattened by the huge traffic numbers, making it impossible to see trends.
By moving the blog post count to a secondary axis, you assign it its own scale. Now, you can clearly see the relationship between your content production and traffic spikes, all in one easy-to-read chart.
Example: Comparing Gross Revenue ($0 - $500,000) with Units Sold (0 - 8,000) for a product launch.
2. Visualizing Different Units of Measurement
Sometimes your datasets are measured in entirely different units that simply can’t share an axis. For instance, maybe you’re tracking average monthly temperature (°F) and total rainfall (inches). There’s no logical way to represent Fahrenheit and inches on the same scale.
A secondary axis lets you display both series together, each with its appropriate unit of measure. This is perfect for showing potential correlations between weather patterns and, for example, monthly ice cream sales or store foot traffic.
Example: Plotting average page load time (in seconds) against the number of support tickets received (a raw count).
3. Showing a Mix of Chart Types (Combo Charts)
Secondary axes are the key to creating effective combination (or "combo") charts. This is where you represent one data series with columns and another with a line. This is incredibly useful for showing raw values against a rate or percentage.
For example, a sales manager might want to visualize monthly sales volume (as columns) and the sales team's sales-to-lead conversion rate (as a line) on the same chart. The sales volume might be in the tens of thousands, while the percentage rate is between 0% and 100%. Plotting them on separate axes with different chart styles makes the relationship between volume and efficiency instantly clear.
Example: Displaying advertising spend ($) as a column chart and the resulting Return on Ad Spend (ROAS) as a line chart.
How to Add a Secondary Axis to an Excel Chart (Step-by-Step)
Let's walk through creating a chart with a secondary axis using a practical example. Say we want to chart our company's monthly sales revenue and the number of units sold. Our data looks like this:
The revenue is in the tens of thousands, while the units sold are in the thousands. This is a perfect example for a secondary axis.
Step 1: Create Your Initial Chart
First, create a standard chart like you normally would. It's often easiest to start with a bar or line chart.
Select your entire data range, including the headers (in our example, A1:C7).
Go to the Insert tab on the Excel ribbon.
In the Charts group, click on the icon for "Insert Column or Bar Chart."
Choose Clustered Column.
Excel will generate a chart. You'll immediately notice the problem: the "Units Sold" columns are tiny compared to the "Sales Revenue" columns.
Step 2: Isolate the Data Series You Want on the Secondary Axis
Next, we need to tell Excel which data series we want to move to the new axis. In this case, it’s "Units Sold."
Right-click on one of the "Units Sold" columns in the chart. Be sure to click the series you want to move.
From the menu that appears, select Change Series Chart Type....
Step 3: Assign the Series to the Secondary Axis
This action opens the "Change Chart Type" dialog box. Excel automatically switches you to the Combo chart section at the bottom of the list. Here, you'll see a row for each of your data series ("Sales Revenue" and "Units Sold").
This is the magic step: find the "Units Sold" series and check the Secondary Axis box on the right-hand side.
You’ll see a live preview of the chart update immediately. A new axis appears on the right, and the "Units Sold" columns are now scaled appropriately to that new axis.
Step 4: Customize the Chart Type for Readability
While assigning the secondary axis fixed the scaling problem, having two sets of columns can still be visually confusing. It’s a best practice to change one of the chart types to make them distinct. A column-and-line combination is classic and effective.
In the same "Change Chart Type" window:
Locate the "Units Sold" series again.
Click the dropdown menu next to its name under "Chart Type."
Select Line or Line with Markers.
The preview updates again, now showing sales revenue as neat columns and units sold as a distinct line overlayed on top. This makes a clear visual distinction between your two metrics.
Step 5: Format Your Chart for Clarity
Click OK to close the dialog box. Your new combination chart with a secondary axis is ready! But don't stop here - a few formatting tweaks will make it infinitely better.
Add Axis Titles: This is not optional, it's essential for anyone trying to understand your chart. Click on the chart, then click the green "+" icon that appears on the right. Check the box for Axis Titles. Then, click on each new title box ("Axis Title") to label your axes clearly (e.g., "Sales Revenue ($)" on the left, and "Number of Units Sold" on the right).
Improve the Legend: Ensure the legend is clear and correctly identifies which data series is columns and which is the line. You can click and drag it to a different position if needed.
Adjust Colors: Use contrasting colors that are easy on the eyes. Match the color of the axis title and labels to the data series it represents for extra clarity.
Best Practices for Using a Secondary Axis
While incredibly useful, a secondary axis can also be misleading if not used thoughtfully. Keep these tips in mind to create charts that inform, not confuse.
Label Everything Clearly
An unlabeled second axis is guaranteed to create confusion. Your audience needs to quickly know what each of the two vertical axes represents. Use the Axis Titles feature to write clear, concise labels that include the unit of measurement ($, %, lbs, etc.).
Use Color and Style to Differentiate Data
Connect your data visually. Make the line chart and its corresponding axis label the same color (e.g., orange). Do the same for the column chart and its axis label (e.g., blue). This immediately tells the viewer which data series corresponds to which scale, reinforcing what your legend shows.
Keep It Simple
Just because you can doesn't mean you should. A dual-axis chart is fantastic for two, and at a stretch, maybe three data series. Adding more than that turns your chart into a jumbled mess of lines and colors, often called a "spaghetti chart." If you need to compare more than two or three types of data, it’s almost always better to create multiple separate charts.
Avoid Misleading Interpretations
Be aware that dual-axis charts can be manipulated - intentionally or not - to imply a relationship that isn't really there. By changing the scale of the axes, you can make two largely unrelated trend lines look almost identical or wildly different. The goal is to show the data objectively, not to force a narrative. Always ensure your scales start at zero if possible and present the information as transparently as you can.
Final Thoughts
Adding a secondary axis is an essential Excel skill for anyone who needs to report on data. It turns a confusing, unreadable chart into a powerful visual tool for comparing metrics with different scales or units, unlocking richer insights from your data.
Drilling down into menus and formatting options in Excel gets the job done but can feel clunky, especially when you need dashboards that update automatically. This process of wrangling data and formatting charts is exactly why we built Graphed. We connect directly to your data sources, allowing you to ask for a dual-axis chart in plain English like, "show me a combo chart of sales revenue as columns and units sold as a line" and get a perfectly formatted, live-updating visualization in seconds. No clicks, no menus, just answers.