What is Previous Period in Looker Studio?

Ever create a dashboard in Looker Studio and immediately get asked, "Is that number good or bad?" A metric like "5,000 site visits" doesn't mean much on its own. Is that up from last month? Down from last year? This article will show you how to add that crucial context using Looker Studio's built-in date comparison features to see your performance against a previous period, the previous year, or any custom date range you need.

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What is a "Previous Period" Comparison?

At its core, a "previous period" comparison is a simple but powerful technique to measure your current data against data from an immediately preceding timeframe. It puts your numbers in context by answering the question, "How are we doing right now compared to how we were doing just before this?"

For example, if you set your report's date range to "This Month," enabling a "previous period" comparison will automatically show you the data from "Last Month" alongside it. This is the foundation of common metrics like:

• Month-over-Month (MoM) Growth: Comparing this month's performance to last month's.
• Week-over-Week (WoW) Growth: Comparing this week's performance to last week's.
• Quarter-over-Quarter (QoQ) Growth: Comparing this quarter to the previous one.

In Looker Studio, this comparison is often shown as a percentage and an absolute number, frequently with color-coded arrows (green for growth, red for decline) to give you an at-a-glance understanding of performance trends.

Why Date Comparisons Are Essential for Good Reporting

Adding date comparisons transforms your dashboard from a static data display into a dynamic performance analysis tool. Without them, you're just looking at numbers. With them, you're uncovering a story.

Here’s why they are so important:

• Provide Immediate Context: Instantly tells anyone viewing the report if the current performance is an improvement, a decline, or holding steady. A 10% MoM increase in leads is a clear signal of positive momentum.
• Spot Trends and Patterns: Are your sales consistently growing month-over-month? Did a recent marketing campaign cause a spike compared to the previous week? Regular comparisons make it easy to see these patterns over time.
• Measure Goals and KPIs: If you have a goal to increase website traffic by 5% each month, MoM comparisons are the most direct way to track your progress.
• Identify Seasonality: By comparing this October's sales to last October's, you learn if the holiday rush is starting earlier or later than usual. This is a classic Year-over-Year (YoY) comparison, which helps you understand seasonal business cycles.

Simply put, a dashboard without date comparisons is incomplete. They are fundamental to making data-driven decisions instead of just reporting raw numbers.

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How to Compare to the Previous Period in Looker Studio (Step-by-Step)

Adding a basic previous period comparison is surprisingly easy. Let’s walk through the steps using a common example: a Scorecard chart showing total users from a Google Analytics data source.

Step 1: Set Up Your Chart and Date Range

First, add a chart to your report canvas. A Scorecard, Time Series chart, or Table works perfectly. Make sure the chart is connected to a data source that contains a date dimension (like 'Date' from Google Analytics).

Select your chart. In the Properties panel on the right, under the Setup tab, find the Default date range section. Let's set this to a common range like Last 28 days.

At this point, your Scorecard will show the total number of users for the last 28 days. It's a single, context-free number.

Step 2: Find and Select "Previous period"

Now for the key step. Directly below the Default date range is the Comparison date range field. Click on it. A dropdown menu will appear with several options.

Choose Previous period.

Step 3: Analyze the Result

Instantly, your Scorecard updates. Beneath the main metric, you'll see a second line showing the percentage change. If you hover over it, you'll see the absolute change as well. Since our main date range was "Last 28 days," Looker Studio has automatically compared this period to the 28 days immediately before it.

You now have a clear MoM-style comparison. For instance, you might see "4,500 Users" and beneath it, a green arrow with "+10%", telling you that traffic is up 10% from the previous 28-day period.

You can apply this same setting to a Time Series chart to see two lines — one for the current period and one for the previous — or to a Table, where a new column will appear showing the percentage change for each row.

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How to Compare to the Previous Year (YoY)

"Previous period" is perfect for sequential timeframes, but what about comparing to the same period in the prior year? This is crucial for businesses with seasonal cycles to understand their true growth trajectory, controlling for things like holidays or weather.

Fortunately, Looker Studio makes YoY comparisons just as easy.

1. Select the chart you want to update (e.g., a Scorecard showing revenue).
2. In the Properties panel, go to the Comparison date range setting again.
3. This time, instead of 'Previous period', select Previous year.

That's it! If your dashboard is filtered for "This Quarter," it will now compare the data to the same quarter from last year. This helps you answer questions like, "Are our Q4 sales this year better than our big Q4 last year?" without being distracted by a potential dip from Q3.

When 'Previous period' and 'Previous year' Align

It's worth noting that if your selected date range is 'This year to date', selecting 'Previous period' will also give you a YoY comparison. In this specific case, the "previous period" is the entire previous year, so the outcome is the same as choosing 'Previous year'.

Using Advanced and Custom Date Comparisons

Sometimes you need more control than the predefined options offer. Imagine you ran a campaign from May 10th to May 25th and want to compare its performance to a "normal" period before the campaign, like April 1st to April 15th. "Previous period" won't work here.

This is where Looker Studio's custom date ranges shine.

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Creating a Custom Fixed-Period Comparison

1. Set your main date range first. For our example, select your chart, click the Default date range, and choose a Custom fixed range of May 10 to May 25. Your chart now shows data only for the campaign period.
2. Set your comparison date range. Now, go to the Comparison date range setting. Click it, select Custom, and then pick a fixed range of April 1 to April 15.
3. Apply and view. Click Apply. Your chart will now compare the specific campaign performance (May 10-25) directly against your chosen "control" period (April 1-15).

This level of granularity is incredibly powerful for isolating the impact of specific events, marketing pushes, or product launches without being constrained by standard monthly or weekly breakdowns.

Pro Tip: Styling Your Comparison Metrics

You can customize how the percentage change appears to make your reports even clearer. With a chart selected, go to the Style tab in the Properties panel. Here, you can:

• Change the color for positive and negative changes (e.g., using brand colors instead of the default green and red).
• Choose to show both the absolute change and the percentage change.
• Hide the comparison label entirely if you only need the numbers.

Final Thoughts

Adding "previous period" and "previous year" comparisons is a fundamental step in elevating a Looker Studio report from a simple data dump to a powerful analysis tool. This simple feature layers in the context needed to understand performance, demonstrates momentum to stakeholders, and helps you make smarter decisions based on real trends.

While Looker Studio is a fantastic tool, getting all your data connected and building these reports across different platforms like Google Ads, Shopify, Facebook Ads, and Salesforce can be a time-consuming, manual process. This is precisely why we created Graphed. We wanted to eliminate the setup drudgery and tedious configuration. Instead of clicking through menus to configure date comparisons, you can simply ask for what you need in plain English - like, "Compare my revenue from Shopify and Facebook Ads month-over-month for the last six months" - and instantly get a dashboard built for you, with all the right comparisons already in place.