How to Make a Double Line Graph in Google Sheets

Comparing two different data trends over the same period is one of the most effective ways to extract meaningful insights. Whether you're a marketer tracking different channels or a business owner monitoring product sales, seeing two metrics side-by-side tells a story that a single data point can't. A double line graph is the perfect tool for this, and this tutorial will walk you through exactly how to create and customize one in Google Sheets.

When Should You Use a Double Line Graph?

Line graphs are designed to show a value changing over time. By adding a second line, you can directly compare how one trend moves in relation to another. This visual comparison can instantly reveal correlations, divergences, or patterns that might otherwise stay buried in a table of numbers.

This is especially useful for:

• Marketing Analytics: Compare website traffic from Organic Search vs. Social Media over the last six months to see which channel is growing faster. Or, plot your Ad Spend vs. Conversions to understand the relationship between investment and return.
• Sales Performance: Track the number of New Leads vs. Closed-Won Deals each month to monitor sales funnel efficiency. You could also compare the performance of two different sales reps or two different territories.
• E-commerce Reporting: Compare the revenue generated by two different product categories over a year to identify seasonal trends or shifts in customer preference.
• Financial Tracking: Plot your company's Revenue vs. Expenses on a quarterly basis to get a clear picture of profitability and cash flow trends.

The key is that both data sets should share the same x-axis, which is almost always a measure of time (days, weeks, months, quarters, etc.). This shared timeline is what makes the comparison meaningful.

Preparing Your Data for a Double Line Graph

Like any chart, a powerful double line graph begins with well-structured data. Forgetting this step is the number one reason charts go wrong in Google Sheets. You need to organize your spreadsheet in a simple, clear format that Google Sheets can easily understand.

Here’s the ideal structure:

• Column A: The X-Axis. This column should contain your timeline - dates, a series of months, years, etc. This is the common thread that connects your two data series.
• Column B: The First Data Series (Y-Axis #1). This column holds the numerical data for your first line. For example, monthly website sessions from "Organic Search."
• Column C: The Second Data Series (Y-Axis #2). This column contains the numerical data for your second line, like monthly sessions from "Paid Social."

Your header row is also important. The titles in this row (e.g., "Month," "Organic Traffic," "Paid Traffic") will be automatically used to label your chart's axes and create the legend, saving you a customization step later.

Your data should look something like this:

Pro Tip: Ensure the date column is correctly formatted as 'Date' (Format > Number > Date). This prevents Google Sheets from treating your timeline as plain text, which can cause plotting errors.

Step-by-Step: Creating Your Double Line Graph in Google Sheets

Once your data is tidy and correctly structured, creating the graph itself takes just a few clicks.

Step 1: Select Your Data

Click on the top-left cell of your data set (A1 in our example, which contains "Month"), and then hold Shift while clicking on the bottom-right cell (C7 for the "May" row's social traffic). This will highlight your entire data range, including the headers.

Step 2: Insert the Chart

With your data selected, navigate to the main menu at the top of the screen and click Insert > Chart. Google Sheets will instantly analyze your selected data and pop up a default chart, along with the Chart editor pane on the right-hand side.

Step 3: Choose the Correct Chart Type

Google Sheets is usually pretty smart and will often default to a Line chart when it recognizes a time-based data series. However, if it suggests a different type of chart, you can easily change it.

In the Chart editor pane on the right, under the Setup tab, find the "Chart type" dropdown menu. Scroll down and select Line chart. Your data will instantly re-format into a double line graph, with each data series represented by its own colored line.

Customizing Your Graph for Maximum Clarity

Your basic chart is now ready, but a few simple customizations can transform it from a functional graph into a professional and easy-to-read data story.

Editing the Chart Title and Axis Labels

A good title is specific and descriptive. Instead of the default "Organic Traffic vs. Social Media Traffic," a title like "Organic vs. Social Media Website Traffic Growth | H1 2024" tells your audience exactly what they are looking at. To edit, simply double-click the chart title to type directly or go to the Customize > Chart & axis titles section in the editor and modify the "Chart title" text.

Adjusting the Lines and Data Points

Maybe your brand uses a specific color palette, or maybe the default blue and red are simply not different enough. You can adjust the appearance of each line individually.

• Go to the Customize > Series tab in the Chart editor.
• Use the dropdown menu to select which series ("Organic Traffic" or "Social Media Traffic") you want to edit.
• Here, you can change the line color, line thickness, and even the point size or shape for each data point on the line. Adding points can make specific monthly values easier to see at a glance.

Improving the Legend and Gridlines

The legend tells the viewer what each colored line represents. By default, it might appear on the right. In the Customize > Legend section, you can change its position to the top, bottom, or inside the chart - whatever looks cleanest. For gridlines, you can adjust their color or spacing under Customize > Gridlines and ticks to make the chart feel less cluttered or more precise.

Common Problems and How to Fix Them

Help! My graph has two separate y-axes or mashed the data together strangely.

This nearly always points back to a data structure issue. Go to the Chart editor's Setup tab. Check that your time column (e.g., "Month") is correctly listed under "X-axis" and that your two data categories are listed as individual "Series." If not, you can click on these fields and manually select the correct ranges from your sheet.

My date labels on the x-axis are overlapping and look messy.

This is common with daily data over a long period. In the editor, go to Customize > Horizontal axis and look for the "Slant labels" option. Setting an angle of 30° or 60° often fixes cluttered labels perfectly.

One of my lines is almost flat on the bottom because its values are so much smaller than the other line.

Let's say you're comparing Website Sessions (in the tens of thousands) to Ad Spend (in the hundreds). The difference in scale will flatten the Ad Spend line. The best solution is a Combo Chart.

In the Chart editor, change your "Chart type" to a "Combo chart." Then, go to Customize > Series. Select the metric with the smaller values (Ad Spend in this case) and, in its options, change the 'Axis' from "Left axis" to "Right axis". This will create a second y-axis on the right just for that metric, allowing both lines to show their trends clearly.

Final Thoughts

Creating a double line graph in Google Sheets is a direct and powerful way to compare two trends over time. Once you master the simple rules of data preparation - a time-based x-axis in the first column followed by your data series - you can instantly generate compelling visuals and use the editor's customization options to make them broadcast a clear and compelling story.

Mastering these steps in Google Sheets is a great skill for one-off analyses, but we know firsthand that this manual work adds up. If you're constantly repeating this process for weekly or monthly reports, building dozens of charts from different ad platforms and analytics tools, you know the cycle of exporting CSVs and formatting spreadsheets can become exhausting. This is exactly why we created Graphed. Instead of setting up the data and building the chart by hand, we simply ask for what we need in plain English - like "Compare revenue from Facebook Ads and Google Ads over the last 90 days as a line chart" - and get a live, interactive dashboard back in seconds.