How to Add a Line to a Chart in Google Sheets

Adding a reference line to your chart in Google Sheets - whether it's a sales goal, an industry benchmark, or just a simple average - can instantly give your data valuable context. Instead of just showing what happened, you can show how it stacks up against what should have happened. This article provides a clear, step-by-step guide to adding horizontal lines for targets, averages, and trendlines to your charts in Google Sheets.

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First, Let's Set Up a Basic Chart

Before you can add a line, you need a chart. Let’s start with a common scenario: tracking monthly sales data. We want to visualize our monthly revenue in a column chart.

Here's our sample data:

To create a bar chart from this data, follow these steps:

1. Highlight the entire data range, including the headers (A1:B7 in our example).
2. Navigate to the top menu and click Insert > Chart.
3. Google Sheets will usually default to a useful chart type. In the Chart Editor on the right, under the Setup tab, make sure Chart type is set to "Column chart."

Now you have a basic column chart showing monthly revenue. It's informative, but lacks context. Let's start adding some lines.

Method 1: Adding a Trendline to Your Chart

The simplest line you can add is a trendline. This is incredibly useful for seeing the general direction your data is moving over time, smoothing out an individual month's highs and lows. Google Sheets has a built-in feature for this.

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Step-by-Step Instructions:

1. Enter the Chart Editor: Double-click anywhere on your existing chart. The Chart editor pane will appear on the right side of your screen.
2. Navigate to Customization: Click on the Customize tab in the editor.
3. Select the Data Series: Expand the Series section. By default, it will be applied to your primary data series (in this case, "Revenue ($)").
4. Add the Trendline: Scroll down within the Series options until you see a checkbox for Trendline. Simply check this box.

A straight, dotted line will immediately appear, showing the upward trajectory of your sales. You can customize this line further right here in the Series menu. Change its type (Linear, Exponential, etc.), line color, opacity, and thickness to make it stand out.

Method 2: Adding a Target Goal or Average Line

While a trendline is automatically generated, adding a custom horizontal line for a goal or an average requires a slightly different approach. You'll need to add a new column to your source data to act as the "data series" for your line. It's easier than it sounds.

Adding a Static Target or Goal Line

Let's say your monthly revenue goal is $55,000. You want a solid horizontal line across your chart to see which months hit the target and which ones fell short.

Step 1: Add a "Goal" Column to Your Data

Go back to your data table and create a new column next to "Revenue." Let's call it "Revenue Goal." In every single cell in this column, enter your target value: 55000. Your data should now look like this:

Step 2: Update Your Chart's Data Range

1. Double-click your chart to open the Chart Editor.
2. Under the Setup tab, find the Data range field.
3. Click the grid icon to select a new data range. Highlight all three columns of your data now (in our example, A1:C7). Click OK.

Your chart will automatically update, but it won't look right yet. Google Sheets will likely add a second set of columns for your goal, which is not what we want.

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Step 3: Convert the Goal Series to a Line

1. With the Chart Editor still open, go back to the Setup tab.
2. Make sure the Chart type is set to Combo chart. This type allows you to mix different chart styles (like columns and lines) in one visualization.
3. Now, switch over to the Customize tab and expand the Series section.
4. You'll now see a dropdown menu. It's likely set to "Revenue ($)". Change this dropdown to "Revenue Goal."
5. In the format options below for the "Revenue Goal" series, change the Type from Columns to Line.

Instantly, the red columns will transform into a sharp horizontal line right at the $55,000 mark. You can now easily adjust its color, thickness, and style to make it visually distinct.

Adding a Dynamic Average Line

What if you don't have a static goal, but want to see how each month performed against the average? The process is almost identical, but instead of typing a fixed number, we'll use the AVERAGE() formula.

Step 1: Add an "Average" Column with a Formula

In a new column named "Average Revenue," you'll use a formula to calculate the average of your revenue data. The key is to use absolute references (with a $ sign) so the formula doesn't change as you copy it down.

In the first cell of your new column (e.g., cell D2), enter the formula:

=AVERAGE($B$2:$B$7)

This formula tells Sheets to always calculate the average of the range from B2 to B7. Drag this formula down to fill the entire column.

Step 2: Update the Chart

Just like with the goal line, simply edit your chart's data range to include this new "Average Revenue" column. Then, in the Customize > Series menu of the Chart Editor, change the chart type for the "Average Revenue" series to a Line.

The beauty of this method is that the average line will automatically update whenever your underlying revenue data changes. If you add new months or adjust old values, the average line recalculates and redraws itself.

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Tips for Making Your Chart Easy to Read

Once your lines are added, a few small tweaks can make a big difference in clarity.

• Use Good Contrast: Make sure your line's color stands out from the columns or bars and the background. A bold color like red, orange, or a dark gray often works well.
• Adjust Line Style: Use a solid line for a hard goal and perhaps a dashed or dotted line for an average or trendline. You can change this in the Customize > Series menu.
• Label Your Axes Clearly: Make sure the Y-axis has a clear label (e.g., "Revenue ($)") so everyone knows what the numbers represent.
• Use Meaningful Legends: Google Sheets automatically creates a legend. Check that it clearly says "Revenue" and "Revenue Goal" or "Average Revenue" so your audience doesn't have to guess.

Final Thoughts

Learning how to add goal, average, and trend lines in Google Sheets is a simple yet powerful way to elevate your reports. It transforms your chart from being just a display of data into a powerful tool for performance analysis, turning raw numbers into an easy-to-understand visual story.

While creating these charts manually is a great skill, we know the real work comes from stitching together data from different sources before you even get to Google Sheets. If you're tired of that manual reporting loop of exporting CSVs from Shopify, Google Analytics, or your ads platforms every week, you might like the AI-powered approach we've built at Graphed. Instead of wrestling with spreadsheet formulas, you can connect your data sources once and just ask in plain English: "Show me a chart of my Shopify revenue vs. my goal of $60k a month." In seconds, we generate a live, real-time dashboard that always stays up to date, giving you back hours of your week.