What is a Sankey Chart in Power BI?

A standard bar chart is great for comparisons, and a pie chart can show parts of a whole, but what happens when you need to visualize a process or a flow? To tell the story of a customer journey, a budget's distribution, or a website's traffic patterns, you need an equally dynamic visual. This article will show you how to use a Sankey chart in Power BI to turn your process data into a clear, compelling visual story.

What is a Sankey Chart?

A Sankey chart is a type of flow diagram that visualizes the movement of values from a starting point (source) to an endpoint (destination). The width of the lines, or 'links', connecting these points is proportional to the quantity of the flow. Think of it like mapping out rivers and their tributaries - the wider the river, the more water it carries. In a business context, instead of water, you might be tracking budget dollars, website users, or product inventory.

Every Sankey chart is made of two core components:

• Nodes: These are the categories at the beginning and end of a flow. In a website traffic report, your source nodes could be channels like "Organic Search," "Paid Social," and "Email," while your destination nodes could be pages like "Homepage," "Pricing Page," or "Blog."
• Links (or Flows): These are the bands that connect a source node to a destination node. The thickness of each link represents its value or weight, instantly showing you the major pathways and contributions within your data.

When to Use a Sankey Chart

Sankey charts are incredibly useful for revealing relationships and pathways within a system. You can use them to answer questions like:

• Website Analytics: Where does my website traffic come from, and which landing pages do users visit first?
• Marketing Campaigns: Which marketing channels are driving the most traffic to my key campaigns, and which of those are leading to the most conversions?
• Budgeting and Finance: How is our company budget distributed across different departments, and where is each department spending its money?
• Sales Funnels: How many leads move from the "New" stage to "Qualified," and from which sources do our most valuable closed deals originate?
• Supply Chain Management: Which factories are supplying which warehouses, and which of those warehouses fulfill the most orders for our top retail locations?

In all these cases, a Sankey helps you visualize not just the totals, but the entire process flow.

Why Bother with a Sankey in Power BI?

While Power BI has dozens of native visuals, taking the time to add a Sankey chart opens up a new level of storytelling for your reports. They aren’t just aesthetically pleasing, they offer distinct analytical advantages.

1. Tell a Clear Story About a Process

A bar chart can show that you received 50,000 visitors from Organic Search last month. A Sankey chart can show you that of those 50,000 visitors, 25,000 landed on your homepage, 15,000 landed on a specific blog post, and 10,000 went directly to a product page. It immediately transforms a simple metric into a narrative about user behavior. This makes it far easier for your stakeholders to understand the journey, not just the outcome.

2. Pinpoint Dominant Paths and Key Drop-offs

Because the flows are sized by value, your audience's eyes are immediately drawn to the most significant pathways in your data. It becomes instantly obvious which channel contributes the most, which product receives the lion’s share of the budget, or which process step is the most critical. Conversely, it also highlights "leaks" in a system - for example, if a large flow enters one node but a much smaller flow exits it on the way to the next stage, you've located a significant drop-off point that needs investigation.

3. Make Complex Data More Intuitive

Imagine a spreadsheet of marketing data with columns for "Channel," "Campaign," and "Conversions." While you could create a pivot table, a Sankey chart immediately visualizes the complex relationships between these fields. It allows even non-technical team members to see, for instance, that while email marketing is a small channel overall, it drives a disproportionately high number of valuable conversions for a specific campaign.

How to Create a Sankey Chart in Power BI: A Step-by-Step Guide

The Sankey chart is not a standard, out-of-the-box visual in Power BI. You'll need to import it from AppSource, Power BI's marketplace for custom visuals. The process is quick and completely free.

Step 1: Import the Sankey Chart from AppSource

First, you need to add the Sankey visual to your Power BI report.

1. On the Visualizations pane in Power BI Desktop, click the three-dot icon (...) at the bottom.
2. Select Get more visuals from the menu.
3. In the AppSource window that opens, use the search bar to type "Sankey."
4. You'll see several options. A popular and reliable choice is the one simply named Sankey chart. Click on it, then click the Add button.
5. Once imported, a new icon for the Sankey chart will appear in your Visualizations pane.

Step 2: Structure Your Data Correctly

To use a Sankey chart, your data needs a specific structure. At a minimum, you must have three columns:

• A "Source" column: Contains the category where the flow begins.
• A "Destination" column: Contains the category where the flow ends.
• A "Value" or "Weight" column: A numeric column that determines the size of the flow.

Here's a simple example of how your data might look for a website traffic analysis:

This simple table provides everything the Sankey chart needs to map the flow of sessions from different sources to different destinations.

Step 3: Drag and Drop Your Fields

Now for the easy part. Click the Sankey chart icon in the Visualizations pane to add a blank visual to your report canvas.

With the new visual selected, look at the fields well in the Visualizations pane. You'll see boxes for Source, Destination, and Weight.

1. Drag your "Source" column (e.g., Source) into the Source field.
2. Drag your "Destination" column (e.g., Destination) into the Destination field.
3. Drag your "Value" column (e.g., Sessions) into the Weight field.

As soon as you drop the fields into place, your Sankey chart will appear on the canvas, showing the flows between your source and destination nodes.

Step 4: Customize for Clarity and Impact

A default Sankey chart is functional, but a little formatting can make it much clearer and more professional. Select the chart and go to the Format your visual tab (the paintbrush icon) in the Visualizations pane.

Here are some key settings to adjust:

• Links: This section lets you control the appearance of the flows. You can change their colors to better group related paths or turn on Data labels to display the actual value on each link. Setting a little transparency can also improve readability if you have many overlapping flows.
• Nodes: Here you can adjust the width of the node rectangles and change the text in the labels (font, color, and size). Be careful not to make the text too large, as it can clutter the visual.
• Scale Settings: If your data has a very wide range of values (e.g., one flow is 1,000,000 and another is 100), enabling the Logarithmic scale can help make the smaller flows more visible.
• Title: Always give your chart a clear, descriptive title. "Website Traffic Flow from Channel to Landing Page" is much better than "Sessions by Source."

Best Practices for Making Your Sankey Chart Shine

Building the chart is one thing, making it effective is another. Keep these tips in mind to avoid common pitfalls.

• Keep It Focused: The biggest mistake with Sankey charts is trying to show too much at once. If you add too many nodes and levels, you end up with a "spaghetti chart" that’s impossible to read. If your data is very complex, use filters to focus on the top 10 flows, or create multiple charts for different segments.
• Order Nodes Logically: Arrange your data so the chart reflects a natural process. Usually, this means flows move from left to right in a logical sequence. It might require adding a sorting or index column in your data model to force the nodes to appear in the desired order.
• Use Color Meaningfully: Don't just assign a random rainbow of colors. Use color to add another layer of information. For example, all nodes related to "Paid" channels could be one color, while "Organic" channels are another. This helps viewers spot patterns more quickly.
• Give Your Chart Context: Don't let your Sankey chart float in space. Surround it with a short text explanation, a clear title, and cards displaying key totals. This helps ensure your audience understands what they're looking at and why it matters.

Final Thoughts

Sankey charts are a fantastic addition to any Power BI report, offering a way to visualize processes and flows that traditional charts can’t match. By importing the visual from AppSource, prepping your data with a source, destination, and weight, you can quickly build powerful narratives around customer journeys, budget allocation, and more, turning complicated data into an intuitive visual story.

While building reports in Power BI is effective, sometimes you need answers without getting stuck in the drag-and-drop process. That's where we've designed Graphed to help. Instead of structuring data and formatting visuals manually, you can just connect your sources and ask questions in plain English, like "Show me the flow of traffic from our top channels to our main landing pages." We build the live, interactive visualizations for you, letting you focus on the insights, not the setup.