How to Make Two Trendlines on One Graph in Excel

Trying to show two different trends on the same Excel graph can feel surprisingly tricky. You have two distinct sets of data, you want to see where each is heading, but the option to just add a second trendline isn't always obvious. This guide cuts through the confusion and shows you exactly how to add two (or more) trendlines to a single chart, providing a clearer picture of your data.

We’ll walk through the most reliable method for creating your chart, explain when and why to use different trendline types, and cover some quick troubleshooting tips for common issues.

Why Add Two Trendlines to One Graph?

Before jumping into the "how," it's helpful to understand the "why." A single trendline shows you the general direction of one data set - is it going up, down, or staying flat? By adding a second trendline, you enable direct comparison, which is fantastic for uncovering relationships and insights that might otherwise be missed. This is a simple but powerful way to tell a compelling story with your data.

Consider a few practical business examples:

• Marketing Analysis: You could plot your monthly marketing spend and new customer acquisitions on the same chart. The two trendlines would instantly show if increased spending is actually leading to a meaningful increase in new business over time.
• Sales Performance: A sales manager could compare the sales growth of two different product lines. Are both growing at the same rate, or is one starting to overtake the other?
• Operational Efficiency: You could track the volume of support tickets against the number of support agents. The two trendlines help visualize if your hiring is keeping pace with customer demand.

In all these cases, comparing the trends, not just the raw data points, offers a much deeper level of understanding.

The Easiest Method: Creating a Multi-Series Scatter Plot

The most straightforward and flexible way to get two trendlines on a single chart is to use a Scatter plot with two distinct data series. A line chart can sometimes work, but a scatter plot handles x- and y-axis data more precisely, which is exactly what we need for accurate trend analysis.

Step 1: Structure Your Data Correctly

Excel needs to understand which data points belong together. The best way to set this up is to have your independent variable (often a time period, like dates or months) in one column, and your two dependent variables in the next two columns.

Imagine you're a marketer at a software company and you want to compare website sessions with the number of free trial signups over the last six months. Your data should look like this:

(Note: Your X-axis, in this case 'Month', needs to be formatted as text, not a date, for the simplest charting experience here).

Step 2: Insert a Scatter Plot

With your data organized, creating the chart is a quick process:

1. Highlight all of your data, including the headers (e.g., cell A1 to C7).
2. Navigate to the Insert tab on Excel’s ribbon.
3. In the Charts section, click on the icon that looks like a plot of dots. This is the Insert Scatter (X, Y) or Bubble Chart option.
4. Select the first option, Scatter.

Excel will instantly generate a chart with two sets of colored dots - one representing your Website Sessions and the other representing Trial Signups. Now you're ready to add the trendlines.

Step 3: Add the First Trendline

Let's add a trendline for the Website Sessions first.

1. In your chart, locate the points representing Website Sessions (they will be one of the two colors).
2. Right-click on any one of those specific data points. A context menu will pop up.
3. Select Add Trendline... from the menu.

Just like that, Excel will draw a line of best fit through those points. Additionally, a Format Trendline pane will appear on the right side of your screen, offering further customization options.

Step 4: Add the Second Trendline

Repeat the exact same process for your second set of data:

1. Now, locate the points representing Trial Signups (the other color).
2. Right-click on any one of those points.
3. Select Add Trendline... from the menu again.

You will now have a second, distinctly colored trendline on your chart, showing the growth trajectory for trial signups. Your chart is now showing both trends simultaneously!

Step 5: Formatting Your Trendlines for Clarity

Two trendlines can look messy if not formatted cleanly. Using the Format Trendline pane, you can make your chart much easier to read:

• Color and Style: Select a trendline to format it. In the pane, under the paint bucket icon (Fill & Line), you can change its color, thickness, and style (e.g., solid vs. dashed). A great practice is to make one trendline dashed to clearly distinguish it from the other.
• Show the Equation: At the bottom of the Trendline Options, you can check the box for "Display Equation on chart" and "Display R-squared value on chart." This adds the mathematical formula for the line and a measure of how well it fits the data - great for more technical reports.

Alternative Case: When Your Data Has Different Scales

What if you're comparing two metrics with completely different scales? For instance, what if your Website Sessions are in the tens of thousands but your monthly advertising spend is in the hundreds? Plotting them on the same axis would squash the ad spend data into a nearly flat line, making it impossible to see the trend.

The solution is a Combo Chart with a secondary axis.

1. Insert a Combo Chart: After highlighting your data, go to Insert > Charts > Recommended Charts. Click the "All Charts" tab and select "Combo" from the list on the left.
2. Assign a Secondary Axis: In the setup window, you'll see your two data series. For the series with the vastly different scale (e.g., Ad Spend), check the box in the "Secondary Axis" column. This creates a new vertical axis on the right side of the chart scaled specifically for that data.
3. Add Trendlines as Before: Once the chart is created, you can right-click on each data series (one will be a line, the other might be columns - both are selectable) and choose "Add Trendline..." just as you did in the scatter plot method.

This approach keeps both data sets readable and allows you to accurately compare their trends, even when the units and values are far apart.

Choosing the Right Type of Trendline

When you add a trendline, Excel opens the "Format Trendline" pane, where "Linear" is selected by default. A straight line is often all you need, but sometimes your data doesn't follow a simple linear path. Here’s a quick guide to the other options:

• Linear: Ideal for data that shows a steady, consistent rate of increase or decrease. This is your standard "line of best fit."
• Logarithmic: Use this when your data increases or decreases quickly at the start, and then begins to level off. For example, the rate of learning a new skill is often rapid at first and then plateaus.
• Polynomial: Excellent for data with clear peaks and valleys. Think of seasonal sales data that goes up during the holidays and then dips. The "Order" setting lets you decide how many curves your trendline should have. (Be careful with setting it too high, it can over-fit the data.)
• Moving Average: This doesn’t provide a predictive line in the same way, but it's fantastic for smoothing out volatile, "noisy" data to help you see the underlying trend more clearly. A 2-period moving average would average the current and previous data point together.

Don't be afraid to click through the different options. The best trendline is usually the one that you can see most closely follows the general path of your data points without being overly complex.

Final Thoughts

Being able to visualize two trends on one graph transforms a flat spreadsheet into a dynamic tool for analysis. By ensuring your data is structured properly and using a scatter or combo chart, you unlock the ability to add and customize an individual trendline for each data series, making it easy to compare growth, assess relationships, and communicate insights effectively.

While mastering tasks like this in Excel is incredibly useful, we know that moving data between platforms, formatting it, and building charts is tedious manual work. We built Graphed to automate this painful reporting process. Instead of working in spreadsheets, you can connect your data sources (like Google Analytics, Shopify, and your CRM) one time, and then just ask for a visual in plain English like, "create a chart comparing Shopify revenue versus Facebook Ad spend for the last quarter and show the trendlines." You get a live, real-time dashboard in seconds, not a static chart you have to rebuild every week.