How to Make a Gantt Chart in Looker

Building a Gantt chart is one of the best ways to visualize a project roadmap, track dependencies, and keep stakeholders aligned. Instead of managing this in a separate, static spreadsheet, creating it directly in Looker lets you use real-time data that lives alongside all your other business metrics. This article will walk you through exactly how to build and customize a functional Gantt chart inside Looker.

What is a Gantt Chart (And Why Build it in Looker)?

At its core, a Gantt chart is a specialized bar chart that illustrates a project schedule over time. Each bar represents a task or activity, and its position and length along the horizontal axis correspond to the task's start date, end date, and overall duration. It shows you what needs to be done, who is doing it, and when.

The real advantage of building this in Looker, rather than a standalone project management tool, comes from data integration. Imagine a Gantt chart where each task is linked to real-time financial data, marketing campaign performance, or live development tickets. This centralized view ensures your project timeline doesn’t exist in a vacuum, it’s connected to the actual business outcomes you’re driving.

Key Components You'll Need

To get started, you’ll need a dataset with at least three key columns:

• Task Name: A text field describing the task (e.g., "Draft Q3 blog posts," "Develop new login page").

• Start Date: A date or timestamp that marks the beginning of the task.

• End Date: A date or timestamp that marks the completion of the task.

Optionally, you can include other fields to make your chart more insightful, such as:

• Assignee: The person or team responsible for the task.

• Project Phase: A category to group related tasks (e.g., "Research," "Design," "Testing").

• Status: The current state of the task (e.g., "On Track," "Delayed," "Complete").

Preparing Your Data for a Gantt Chart

Looker visualizations depend entirely on well-structured data. Before you can build anything, you need to make sure your underlying data table has the necessary fields and that they are formatted correctly. A messy data source is the number one reason charts fail to render as expected.

The Ideal Data Structure

Your source data, whether from a database, a Google Sheet, or your project management tool's API, should look something like this:

Crucial Tip: Check Your Date Formats

The most common issue users face is incorrectly formatted dates. Looker needs to clearly recognize your start_date and end_date fields as dates. In your LookML model, ensure these fields are defined with the appropriate type: time and a timeframe specified (e.g., date, day_of_month, etc.). Without correctly typed date fields, Looker won't be able to plot anything on a chronological axis.

Step-by-Step Guide: Creating a Gantt Chart with the Timeline Visualization

While Looker doesn't have a visualization option explicitly named "Gantt," its built-in Timeline chart is perfectly designed for this job. Here’s how to configure it in just a few clicks.

1. Start a New Explore and Select Your Fields

Begin by navigating to the Explore in Looker that contains your project data. From the field picker on the left, select the dimensions and measures needed for your chart. At a minimum, you must include:

• The dimension representing your Task Name.

• The timeframe for the Start Date.

• The timeframe for the End Date.

2. Run the Query and Select the Timeline Chart

Once your fields are selected, click the Run button. Looker will generate a data table with your results. Next, in the Visualization pane, toggle to the chart options by clicking on the three dots (...) and select Timeline from the list of available chart types.

Initially, it might not look right, but that's what the settings panel is for.

3. Configure the Viz Settings to Build Your Gantt Chart

With the Timeline visualization selected, click the Edit button in the top right of the Visualization pane. This is where you map your data fields to the chart’s display elements. You'll see several dropdown menus:

• Label Field: Choose the dimension that contains your task names (e.g., task_name). This will serve as the label for each bar on the chart.

• Start Field: Select your Start Date timeframe (e.g., start_date).

• End Field: Select your End Date timeframe (e.g., end_date).

As you map these fields correctly, your visualization will transform into a fully functional Gantt chart, showing each task as a horizontal bar spanning its start and end dates.

Customizing and Enhancing Your Looker Gantt Chart

A basic chart is good, but a well-customized one provides much deeper insight at a glance. Let’s explore a few easy customizations in the Timeline visualization settings.

Grouping Tasks for Clarity

The real power of a Looker Gantt chart comes from organizing your tasks into logical groups. In the settings panel, you'll find a dropdown for Group By. You can use this to group tasks by any dimension in your data.

• Group by Project Phase: This creates clear swimlanes for each stage of your project (e.g., "Discovery," "Implementation," "Launch").

• Group by Assignee: This is perfect for understanding team workload and seeing who is responsible for which tasks at a glance.

As soon as you select a dimension to group by, Looker will reorganize your chart, neatly color-coding and sectioning the task bars automatically.

Visualizing Project Milestones

Milestones are crucial points in a project timeline, like a launch date or a key deliverable. Creating them on your Gantt chart is simple.

To create a milestone, just add a task in your source data where the start_date is the same as the end_date. In the Timeline visualization, this will appear as a very thin vertical slice or point - a perfect landmark.

Example Milestone Data:

"Go Live Launch", 2024-11-15, 2024-11-15

Making Tooltips More Useful

When you hover over a bar in your Gantt chart, Looker displays a tooltip. By default, it shows the data you’ve already included in the chart. You can make this much more informative by adding extra fields to your Explore without having them clutter the main chart.

For instance, add fields like Completion Percentage, Budget Allocated, and Task Status to your query. Even though these fields aren't explicitly mapped in the visualization settings, they will automatically appear in the hover-over tooltip, providing instant, deeper context on any task.

Common Challenges and How to Solve Them

Sometimes things don't go as planned. Here are a few common issues and their quick fixes.

• "My Chart is Blank or Shows Weird Dates": This is almost always a data formatting problem. Go back to your underlying data or your LookML model and double-check that your date fields have the correct type and are in a YYYY-MM-DD or similar standard format recognized by Looker.

• "My Gantt Chart is Way Too Crowded": If you're managing a large project with hundreds of tasks, the chart can quickly become unreadable. Use Looker's filters at the top of the Explore to narrow down your view. Create filters for Project Name, Team Member, or date range, so you and your team can focus on just the relevant tasks.

• "Some of My Tasks Aren't Appearing": The Timeline visualization cannot plot tasks that are missing a start_date or end_date. Null values will be ignored. Make sure every task that should be on the chart has a valid entry in both date columns. If an end date isn't set yet, you can use a COALESCE function in a custom field to substitute today's date as a placeholder to prevent breaking your view.

Final Thoughts

Using Looker's Timeline visualization is a powerful way to turn your raw project data into a dynamic, shareable Gantt chart. You can track progress in real-time and situate your project timelines right next to all the other KPIs that matter to your business, without having to switch between tools.

Of course, building dashboards and handling data prep in BI tools like Looker is still a manual process. This is exactly what we set out to solve with Graphed. Instead of clicking through menus and configuring charts step-by-step, we've enabled marketing and sales teams to connect their tools and get insights quickly. If you feel stuck pulling together reports, try Graphed, where data analysis works in seconds, not hours.