How to Make a Circle Chart in Looker with AI

Creating a clear chart to show parts of a whole is a common task, and the classic circle chart - also known as a pie or donut chart - is a go-to choice for visualizing percentages. This guide will walk you through creating a circle chart in Looker Studio step-by-step. We'll also cover some best practices and look at how new AI features can speed up the entire process.

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What is a Circle Chart and When Should You Use One?

A circle chart displays data as a circle divided into slices, where each slice represents a category and its size corresponds to its percentage of the total. Think of it like a pizza: the entire pizza is 100% of your data, and each slice is a specific data category, like traffic from organic search or sales from a particular product.

There are two main types:

• Pie Chart: A full circle, completely filled in.
• Donut Chart: A pie chart with a hole in the middle, which can be used to display a summary metric, like the total number of users or sales.

While popular, circle charts aren't always the best tool for the job. They work best under specific conditions:

• You're showing parts of a whole: They excel at illustrating proportions. For example, the percentage of your website traffic coming from different channels (Organic, Paid, Direct, Social).
• You have a small number of categories: If you have more than five to seven slices, the chart becomes cluttered and difficult to read. The labels overlap, and comparing the size of small slices becomes nearly impossible.
• The values are meaningfully different: If you have several categories that are all around 15-20%, a bar chart is often much better for showing the subtle differences side-by-side. Our eyes are better at comparing the lengths of bars than they are at judging the area of pie slices.

If your goal is to compare values between categories rather than show their proportion to the whole, a bar or column chart is almost always a better choice.

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Getting Your Data Ready for Looker Studio

Before you can build your chart, you need to make sure your data is structured correctly. A circle chart requires two main components from your data source:

• A Dimension: This is the categorical data that will define your slices. It's the "what" you are measuring. Examples include Traffic Source, Device Category, Country, or Product Name.
• A Metric: This is the numerical data that determines the size of each slice. It's the "how much" of what you're measuring. Examples include Users, Sessions, Revenue, or Pageviews.

For example, to visualize website traffic sources, you’d need a dataset that looks something like this:

Looker Studio will automatically calculate the percentage for each dimension based on its metric value relative to the total. In the example above, the total number of users is 20,900, so "Organic Search" would be the largest slice, representing just over 50% of the pie.

Step-by-Step Guide to Making a Circle Chart in Looker Studio

Creating a circle chart is a straightforward process. Let's walk through it using our traffic source example.

Step 1: Create a New Report and Connect Your Data

First, open Looker Studio and start a new, blank report. Looker will immediately prompt you to connect a data source. You can choose from dozens of connectors, but for this walkthrough, we'll use a common one: Google Analytics. Select the Google Analytics connector, then choose the account, property, and view you want to analyze.

Step 2: Add a Circle Chart to the Canvas

Once your data is connected, click "Add a chart" from the top menu. In the dropdown, you’ll see options for "Pie" and "Donut." For this example, let's select Donut chart. Click it, then click anywhere on your report canvas to place the new chart.

Looker Studio will automatically populate the chart with some default dimension and metric, like "Event name" and "Views." Now, we need to replace those with the data we want to see.

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Step 3: Configure Your Dimension and Metric

With your new chart selected, a "Chart" configuration panel will appear on the right side of your screen. This is where you tell the chart what data to display.

1. Set the Dimension: The "Dimension" field is under the "Setup" tab. Remove the default dimension by clicking the "X" and then search for "Session source / medium" (a common Google Analytics dimension for traffic channels). Drag it into the Dimension field.
2. Set the Metric: Right below the Dimension, you'll find the "Metric" field. Remove the default metric and search for "Active users" or "Sessions." Drag your chosen metric into the field.

Your donut chart should now update instantly, showing you a breakdown of your website users by traffic source. Each slice will represent a source, and its size will be determined by the number of users it brought in.

Step 4: Customize Your Chart for Clarity

The default chart is functional, but a few styling tweaks can make it much easier to read. Switch to the "Style" tab in the chart configuration panel to make adjustments.

• Manage Slices: Looker allows you to set the maximum number of slices. If you have a dimension with many small categories, this is incredibly useful. Set "Slices" to 5 or 6, and Looker will automatically group the smallest categories into an "Other" slice, keeping your chart clean and readable.
• Adjust Colors: You can change the color of each slice to match your brand's palette or to highlight a specific category. Under "Color by," you can select "Slice Order" to assign colors sequentially from your theme or "Dimension values" to assign specific colors to specific categories (e.g., always make "Organic Search" green).
• Improve Labels: The "Labels" section is where you can make the biggest impact. By default, it might only show the category name. Change the "Slice Label" dropdown to show "Percentage" or "Value." Showing the percentage directly on the slice is often more effective than forcing viewers to hunt for it in a legend. You can also adjust font size and color here.
• Position the Legend: Under "Legend," you can change its position (top, bottom, right, or none) and alignment. If you've already labeled your slices clearly with percentages and categories, you might not even need a legend, and setting it to "none" can give your chart more room to breathe.

Using AI in Looker to Create Charts Faster

While the manual step-by-step process offers maximum control, you don't always have to build charts from scratch anymore. Modern business intelligence tools, including Looker, are integrating generative AI to help you create visualizations with natural language.

Inside Looker, a feature powered by Gemini allows you to simply describe the chart you want in plain English. For example, instead of manually going through the steps above, you could type a prompt like:

Create a donut chart showing the breakdown of users by traffic source for last month

Gemini will interpret your request, select the correct dimension and metric from your data source, and generate the chart for you. This significantly speeds up the process, especially for exploratory analysis where you just want a quick look at the data without going through a multi-step setup.

This approach lowers the barrier to entry, letting team members who aren't data experts quickly build their own reports. While AI-generated charts might still need some manual fine-tuning in the "Style" tab to get them perfect, they handle the most time-consuming parts of the initial setup, moving you straight to the insights.

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Best Practices for Readable and Honest Circle Charts

To make sure your circle charts are effective and not misleading, follow these simple rules:

• Don't Use 3D Effects: Never use a 3D pie chart. The perspective effect distorts the true proportions of the slices, tricking the viewer's eye. Slices in the "front" appear larger than they actually are, which is misleading.
• Order Slices Logically: Arrange the slices in a way that makes sense. A common method is to order them from largest to smallest, starting at the 12 o'clock position and moving clockwise. This makes comparison easier.
• Consolidate Small Slices: As mentioned before, use the "Other" category. If you have a slice representing only 1% or 2% of the total, it will just be a tiny, unreadable sliver. Grouping these small pieces together makes the entire chart cleaner.
• Always Add Context: A chart without a title is meaningless. Your title should clearly explain what the chart is showing, like "Website Traffic by Source - Last 30 Days." It's also helpful to include the total value that the percentages are based on (e.g., "Total Users: 20,900"). This gives viewers immediate context for the numbers they're seeing.

Final Thoughts

Creating a circle chart in Looker Studio is a simple process of connecting your data, choosing a chart type, and configuring your dimensions and metrics. By applying a few best practices - like keeping it simple, labeling clearly, and avoiding 3D effects - you can create an effective visual that clearly communicates parts-to-whole relationships in your data.

AI features in tools like Looker offer a glimpse into the future of data analysis, where tedious setup is automated. We designed Graphed around this exact idea - instead of just creating one chart, you can use natural language to build and chat with entire live dashboards connected to all your data sources. You can ask "Show me my top traffic sources" and then immediately follow up with "Which ones are driving the most revenue?" without ever leaving the chat, building a powerful, unified view of your business in seconds, not hours.