How to Add a Line to a Graph in Excel

Adding a line to an Excel graph is a simple way to give your raw numbers a powerful layer of context. Whether you want to show a clear trend, compare against a goal, or track an average, a simple line can turn a good chart into a great one. This guide will walk you through a few different methods for adding lines to your charts, from start to finish.

Why Bother Adding a Line to a Graph?

Before diving into the "how," let's quickly cover the "why." A chart with only bars or dots shows a snapshot, but adding a line helps tell a story. Here are a few common reasons to add one:

• To illustrate a trend: If you have monthly sales data in a column chart, a linear trendline can instantly show whether sales are generally increasing, decreasing, or stagnating over time.
• To highlight a target or goal: A flat, horizontal line can represent your sales quota, your website traffic goal, or your target budget, making it crystal clear how actual performance measures up.
• To show an average: Adding an average line across your dataset helps you quickly spot high and low-performing periods without needing to calculate the average mentally.
• To compare two different kinds of data: You might want to see your monthly advertising spend (as a line) against your leads generated (as columns). Combining chart types helps visualize the relationship between two different data series.

Let's get into the practical, step-by-step methods for creating these in Excel.

Method 1: Adding a New Data Series as a Line Chart

This is the most common reason to add a line to an existing chart, like a column or bar graph. You're effectively creating a "combo chart" that displays two different datasets in two different ways. A perfect example is showing monthly revenue as bars and your monthly sales target as a single line.

Step 1: Get Your Data Ready

First, you need to set up your spreadsheet with the data for both the main chart and the line you want to add. Make sure the data for your line is in a new column right next to your existing chart data. This makes it much easier for Excel to understand.

Imagine you have this simple data for monthly sales:

Here, the "Sales Target" column contains the information we want to turn into a line. Notice how the target value is the same for each month - this will create a straight, horizontal line.

Step 2: Add the New Data to Your Existing Chart

If you already have a chart made with just the "Sales" data, you need to add the "Sales Target" data series to it. If you haven't created a chart yet, select all three columns (Month, Sales, and Sales Target) and insert a Clustered Column chart. If you do that, you can skip to Step 3.

Assuming you have a chart already, here’s how to add the new data:

1. Right-click anywhere on the chart area and choose "Select Data..." from the menu.
2. The Select Data Source window will appear. On the left side, under "Legend Entries (Series)," click the "Add" button.
3. This opens the Edit Series window. Now, you’ll fill in two fields:
4. Click OK, then click OK again on the Select Data Source window.

You’ll now see your chart has a second set of columns next to your sales data. Don't worry, we're about to turn them into a line.

Step 3: Change the New Series to a Line Chart

This is where the magic happens. Excel's "Combo Chart" feature lets you assign different chart types to different data series within the same graph.

1. Find the new data columns you just added to your chart (in our case, the orange "Sales Target" columns).
2. Right-click on any one of those new columns and choose "Change Series Chart Type..."
3. Excel will open the Change Chart Type window and automatically take you to the "Combo" tab on the left.
4. At the bottom of this window, you’ll see a list of your data series ("Sales" and "Sales Target"). Next to each name is a dropdown menu for its chart type.
5. Find your "Sales Target" series and change its chart type from "Clustered Column" to "Line" from the dropdown menu.
6. Click OK.

That's it! Your column chart now has a clean horizontal line running through it, clearly showing your sales target. You can use this same exact process to show an average or compare any two datasets.

Method 2: Adding a Trendline to Your Data

What if you don't have a separate dataset to add? What if you just want to see the underlying trend of the data you already have graphed? This is where trendlines come in handy. A trendline analyzes your existing data points and calculates a single line that represents the general direction of that data.

This method is best for line charts or scatter plots, where you're analyzing data over time or correlation between variables.

Step 1: Select the Data Series

First, click once on the existing line or the specific bars in your chart you want to analyze. This tells Excel which data to use for creating the trendline.

Step 2: Add the Trendline Element

You have two easy ways to add a trendline:

The Quick Way (Using the '+' Button):

1. Once your chart is selected, you'll see a green plus sign ("+") appear in the top-right corner. Click it to open the Chart Elements menu.
2. Find "Trendline" in the list and check the box next to it.

Excel will automatically add a standard linear trendline to your selected data series.

The Ribbon Method (More Options):

1. With your chart selected, go to the "Chart Design" tab that appears at the top of Excel.
2. On the far left, click the "Add Chart Element" button.
3. Hover your cursor over "Trendline" and choose from the available types:

Choose "Linear" if you're unsure. You can always change it later.

Step 3: Customize Your Trendline (Optional)

Once your trendline is on the chart, you can customize it.

1. Right-click on the trendline itself and select "Format Trendline...".
2. A formatting pane will open on the right side of Excel. Here, you can change the color, width, and dash type of the line to make it more visually distinct.
3. You can also do statistical forecasting by entering a number in the "Forward" or "Backward" fields under "Forecast," which extends your trendline into the future or past.

Helpful Tips for Working with Lines in Excel Charts

You'll often run into a couple of common scenarios when working with combo charts. Here’s how to handle them.

When to Use a Secondary Axis

Sometimes you need to visualize two datasets with wildly different scales. For example, you might track the Number of Units Sold (ranging from 100-500) and the Average Sale Price (ranging from $5-$10). If you plot both on the same Y-axis, the sale price line will look flat and uselessly low.

The solution is a secondary axis. This creates a new vertical axis on the right side of your chart specifically for your line.

To enable it, follow the steps in Method 1 to bring up the "Change Series Chart Type" (Combo) window. In the list of your data series, simply check the box in the "Secondary Axis" column for your line graph series. Excel will handle the rest.

Formatting Your Line for Readability

Don’t just stick with Excel’s defaults. A little formatting can make your chart much easier to understand. Right-click on your line and select “Format Data Series...” to open the formatting pane. Try these adjustments:

• For a target or goal line: Change the "Dash type" to a dotted or dashed line. This visually separates it from your actual data.
• For an important data series: Make the line color more vibrant or increase its "Width" to make it stand out.
• For a cluttered chart: Remove the "Markers" (the dots on each data point) by going to Marker Options and selecting "None". This can make a line look sleeker.

Final Thoughts

Adding a line to a chart in Excel is an invaluable skill for anyone who works with data. By either adding a new data series to create a combo chart or adding a calculated trendline, you can offer valuable context that helps others (and yourself) draw the right conclusions quickly.

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