How to Add Comparison in Looker Studio

A static number on a dashboard doesn't tell you much. Seeing that you had 5,000 website visitors last month is a start, but knowing if that's an improvement or a decline is where the real insights are found. Adding comparisons to your Looker Studio (formerly Google Data Studio) reports transforms flat data into a powerful story of performance over time. This guide will walk you through several methods for creating comparisons, from simple date ranges to more advanced segment analysis.

Why Comparisons are Essential in Your Reports

Numbers need context. Without comparing a current metric to a previous period, a budget, or another segment, you're looking at data in a vacuum. A comparison gives a number its meaning by answering the fundamental question: "Is this good or bad?"

Here's why this is so important:

• Performance Tracking: The most obvious benefit is tracking growth. Comparing this month's sales to last month's, or this quarter's lead conversions to the same quarter last year, immediately tells you if you're on the right track.
• Spotting Trends & Anomalies: Is that sudden spike in traffic a one-time event or the start of a new trend? Comparing it to previous periods helps you differentiate between a normal fluctuation and a significant change that needs investigation.
• Providing Perspective: Telling your boss "we spent $10,000 on ads" is information. Telling them "we spent $10,000 and generated 25% more revenue than the previous period with the same budget" is an insight that justifies your work.

In short, comparisons turn your dashboard from a simple data repository into a decision-making tool.

Method 1: The Quick & Easy Date Range Comparison

Looker Studio has a fantastic built-in feature for one of the most common types of comparisons: time periods. This allows you to add a comparison to almost any chart type (scorecards, tables, time series charts, etc.) with just a few clicks. It's perfect for answering questions like "How did we do this month compared to last month?" or "How is our year-over-year growth?"

Step-by-Step Guide to Adding a Comparison Date Range

Let's use a common example: comparing brand keyword searches in Google Search Console this month versus last month.

1. Select Your Chart: Click on the chart you want to add a comparison to. For this example, a "Scorecard" showing Total Clicks is a great choice.
2. Find the Comparison Date Range Setting: With the chart selected, look at the Setup panel on the right side of your screen. Scroll down until you find the "Default date range" section. Just below it, you'll see a field called Comparison date range. It will likely say "None."
3. Choose Your Comparison Period: Click on "None" to open the date range options. You have several powerful choices:
4. Apply and Interpret: Select "Previous period" and click "Apply." Instantly, your scorecard will update. You'll not only see the current value (e.g., "1.2K Total Clicks") but also a new line underneath showing the percentage change from the previous period, often accompanied by a green or red arrow indicating positive or negative change. Voila! You've just added valuable context to your data.

This simple method is the workhorse of dashboard comparisons. You can apply it to time series charts to see last month's trend line overlaid on this month's, or to a table to see how each page on your website performed this week versus last week.

Method 2: Comparing Segments with Data Blending

What if you want to compare something other than dates? For instance, perhaps you want to compare performance between two different audience segments, like mobile traffic vs. desktop traffic, or the performance of two different marketing campaigns side-by-side.

For this task, the built-in date range comparison won't work. We need a more powerful feature: Data Blending. Data blending allows you to "merge" two or more data sources (or copies of the same data source) based on a common key. This sounds complex, but it's a way to line up your data so you can compare apples to apples.

Let's walk through comparing website sessions from organic search traffic versus paid search traffic over time.

Step-by-Step Guide to Segment Comparison using Data Blending

Our goal is to create one time series chart with two lines: one for Organic Sessions and one for Paid Sessions.

1. Set Up Your Base Tables

First, we need to isolate our two segments. The easiest way to start is by creating two identical tables on your report canvas:

• Add a table from your Google Analytics 4 data source.
• Set the dimension to Date.
• Set the metric to Sessions.
• Now, copy and paste that table so you have two identical tables next to each other. These are our temporary building blocks.

2. Filter Each Table to Isolate a Segment

Now, we'll tell each table to only show data for its specific segment:

• For the first table (Organic): Select it. In the Setup panel on the right, scroll to the bottom and click "+ Add a filter."
• Name your filter something clear like "Organic Traffic Filter." Set it to Include > Default Channel Grouping > Equals (=) > Organic Search. Click save. This table now shows only organic sessions by date.
• For the second table (Paid): Select the other table and repeat the process. Create a filter named "Paid Traffic Filter" and set it to Include > Default Channel Grouping > Equals (=) > Paid Search. Click save.

You now have two separate tables, each representing one of the segments you want to compare.

3. Blend the Filtered Data

This is where the magic happens. We're going to merge these two filtered tables into a new, combined data source:

• Hold down the Shift or Command/Control key and click on both tables to select them.
• Right-click on either of the selected tables.
• In the context menu, choose Blend data.

Looker Studio will think for a moment and then create a new, blended data object in the background and might even replace one of your tables with a new blended chart. Go ahead and delete whatever chart it creates, we'll make a fresh one.

4. Build Your Comparison Chart

Now you can create the visual comparison:

• Add a new Time series chart to your report canvas.
• When you add it, it will pick a default data source. With the new chart selected, go to the Setup panel and, in the Data source section, click the current source's name. In the options that appear, select your new "Blended Data" source (it's usually at the top of the list).
• Your chart will try to auto-populate. Let's configure it correctly. Set the Dimension to Date (this is our common "join key").
• Now for the metrics. You will see "Sessions" listed twice—one for organic and one for paid. Drag both over as metrics. To avoid confusion, rename them! Click the small pencil icon next to each metric's name and change one to "Organic Sessions" and the other to "Paid Sessions."

You now have a single chart with two separate lines, perfectly visualizing the performance of your paid vs. organic traffic over your selected date range. You've successfully created a powerful segment comparison.

Method 3: Dynamic Comparisons with Controls and Parameters

Our last method is the most advanced but also the most flexible for the person viewing your report. What if you wanted to allow your audience to choose what they compare? For instance, let them pick from a dropdown to compare any two marketing channels, or any two countries.

This is achievable using Parameters. A parameter adds a variable to your report that can be changed by the viewer using a control element (like a dropdown list).

Imagine we want to create two scorecards an executive can use to compare revenue from any two device categories (Mobile, Desktop, Tablet) they choose.

How to Set up a Dynamic Comparison Control

1. Create Two Parameters:
2. Create Two Calculated Fields:
3. Add Controls to Your Report:
4. Build the Scorecards:

Now, your viewers can use the two dropdowns at the top of the report to select any combination of device categories, and the scorecards will instantly update to show the revenue for each one, allowing for truly dynamic, "on-the-fly" comparisons without ever needing to go into edit mode. This is the ultimate way to empower your end-users to explore the data for themselves.

Final Thoughts

Adding comparisons moves your data from simply reporting what happened to explaining its significance. Whether you use Looker Studio's simple date range feature for quick month-over-month checks, master data blending for segment analysis, or build dynamic controls with parameters, providing context is what turns a good dashboard into an indispensable one.

While these methods are powerful, setting them up in BI tools can be time-consuming and comes with a learning curve. That's why we built Graphed to remove the friction. Instead of manually creating data blends or configuring parameters, with us, you can just ask in plain English: "Create a time series chart comparing sessions from mobile versus desktop traffic from last quarter," and we instantly generate the live, interactive chart for you. We connect your data sources in seconds, empowering your entire team to ask questions and get insights without needing to become technical experts.