Data visualization helps analysts transform complex datasets into meaningful insights. While bar charts, line charts, and pie charts are commonly used for comparisons and trends, some analytical problems require a different approach that focuses on movement and flow.
This is where Sankey diagrams excel.
Sankey diagrams help analysts visualize how quantities move from one stage to another. Whether you’re tracking customer journeys, website navigation paths, sales funnels, or data flows, Sankey diagrams make it easier to understand how resources, users, or values travel through a system.
Sankey diagrams are flow-based visualizations that show how quantities move between stages or categories. In analytics, they are commonly used to analyze customer journeys, website navigation, sales funnels, resource allocation, process flows, and data movement by representing flow volume through link thickness.
In this guide, you’ll learn what Sankey diagrams are, how they work, their advantages, common use cases, and best practices for using them effectively in analytics.
What Is a Sankey Diagram?
A Sankey diagram is a flow chart where the width of each connection represents the quantity moving between nodes.
The thicker the connection, the larger the flow.
A Sankey diagram typically consists of:
- Nodes (stages, categories, or entities)
- Links (connections between nodes)
- Flow values (quantities moving through connections)
Unlike traditional charts that focus on comparisons, Sankey diagrams emphasize movement and transitions.
For example:
Website Visitors
|
├── Product Pages
| ├── Add to Cart
| └── Exit Website
|
└── Blog Pages
├── Newsletter Signup
└── Exit Website
The width of each path represents the number of users following that route.
Why Sankey Diagrams Are Valuable in Analytics
Many datasets involve movement between stages.
Examples include:
- Customer journeys
- Marketing funnels
- Manufacturing processes
- Supply chains
- Energy consumption
- Data pipelines
Traditional charts often fail to show how values move through these processes.
Sankey diagrams provide a visual representation of:
- Origins
- Destinations
- Drop-offs
- Bottlenecks
- Flow volumes
This makes them particularly useful for understanding complex systems.
Key Components of a Sankey Diagram
Nodes
Nodes represent stages or categories.
Examples include:
- Traffic sources
- Website pages
- Departments
- Products
- Sales funnel stages
Links
Links connect nodes together.
They show movement from one stage to another.
Flow Width
The thickness of a link indicates volume.
For example:
- 1,000 visitors → Homepage
- 700 visitors → Product Page
- 300 visitors → Exit
The flow to the Product Page appears wider because it carries a larger volume.
Common Uses of Sankey Diagrams in Analytics
1. Customer Journey Analysis
One of the most popular uses of Sankey diagrams is customer journey visualization.
Businesses can track how users move through:
- Landing pages
- Product pages
- Checkout processes
- Subscription funnels
This helps identify:
- Popular paths
- Abandonment points
- Conversion opportunities
Example
An e-commerce company may discover:
- 10,000 users visit the homepage
- 6,000 view products
- 2,500 add items to cart
- 1,200 complete purchases
A Sankey diagram clearly highlights where users drop off.
2. Website Navigation Analysis
Web analysts use Sankey diagrams to understand user behavior.
Questions they can answer include:
- Which pages attract the most traffic?
- Where do users go next?
- Which pages cause visitors to leave?
This information helps improve website structure and user experience.
Example
A content website may find that visitors who read tutorial articles are more likely to visit product pages than visitors who read news articles.
3. Marketing Funnel Analysis
Marketing teams frequently use Sankey diagrams to visualize lead progression.
Typical stages include:
- Ad impressions
- Website visits
- Lead generation
- Product demos
- Sales conversions
The diagram reveals where prospects are lost during the funnel.
Benefits
- Improves campaign optimization
- Identifies weak funnel stages
- Supports budget allocation decisions
4. Data Pipeline Monitoring
Data engineers often use Sankey diagrams to visualize data movement between systems.
Examples include:
- Source systems
- ETL processes
- Data lakes
- Data warehouses
- Analytics tools
This helps teams identify:
- Bottlenecks
- Failed processes
- Data loss points
Example
A company may track how customer data flows from a CRM into a cloud data warehouse and eventually into reporting dashboards.
5. Financial Analytics
Finance teams use Sankey diagrams to analyze the movement of money.
Common applications include:
- Budget allocation
- Revenue distribution
- Expense breakdowns
- Investment flows
Example
A business may visualize:
- Revenue sources
- Operational expenses
- Marketing costs
- Profit allocation
This provides a clear picture of where funds originate and how they are spent.
6. Supply Chain Analytics
Supply chain professionals use Sankey diagrams to understand product movement.
Examples include:
- Suppliers
- Warehouses
- Distribution centers
- Retail locations
The visualization helps identify inefficiencies and optimize logistics operations.
7. Human Resources Analytics
HR teams can use Sankey diagrams to track employee movement.
Examples include:
- Recruitment sources
- Hiring stages
- Promotions
- Department transfers
- Employee exits
This helps organizations improve workforce planning.
Benefits of Using Sankey Diagrams
Easy Flow Visualization
Sankey diagrams simplify complex movements and relationships.
Highlights Bottlenecks
Large drop-offs become immediately visible.
Supports Decision-Making
Decision-makers can identify opportunities for optimization.
Handles Complex Processes
Unlike basic charts, Sankey diagrams can represent multi-stage workflows effectively.
Limitations of Sankey Diagrams
Despite their strengths, Sankey diagrams are not suitable for every situation.
Can Become Cluttered
Large datasets with many categories can become difficult to read.
Limited for Precise Comparisons
Bar charts often provide more accurate value comparisons.
Not Ideal for Time-Series Data
Line charts remain the preferred choice for trends over time.
Best Practices for Creating Sankey Diagrams
Limit the Number of Nodes
Too many nodes reduce readability.
Use Meaningful Categories
Group similar categories when possible.
Focus on Important Flows
Avoid displaying insignificant pathways.
Use Consistent Labels
Clear labeling improves interpretation.
Highlight Key Insights
Draw attention to major drop-offs, bottlenecks, or high-volume flows.
Sankey Diagrams vs Other Visualization Types
| Chart Type | Best Use Case |
|---|---|
| Sankey Diagram | Flow analysis |
| Bar Chart | Category comparison |
| Line Chart | Trend analysis |
| Pie Chart | Part-to-whole relationships |
| Funnel Chart | Conversion stages |
| Network Graph | Complex relationships |
Choosing the right chart depends on the question you’re trying to answer.
Popular Tools for Creating Sankey Diagrams
Many analytics platforms support Sankey diagrams.
Popular options include:
- Microsoft Power BI
- Tableau
- Google Looker Studio
- Python Plotly
- Python Matplotlib
- D3.js
These tools allow analysts to build interactive Sankey visualizations for business reporting and analysis.
Real-World Example
Imagine an online education platform.
User flow data shows:
- 20,000 Homepage Visits
- 12,000 Course Page Visits
- 5,000 Free Trial Signups
- 2,000 Paid Subscriptions
A Sankey diagram immediately reveals where users drop off and where optimization efforts should focus.
Without a Sankey diagram, understanding these transitions may require reviewing multiple reports and charts.
Sankey diagrams are powerful visualizations for analyzing how quantities move through systems, processes, and workflows. By representing flow volume through link thickness, they help analysts identify bottlenecks, drop-offs, and high-value pathways that may be difficult to spot using traditional charts.
Whether you’re analyzing customer journeys, marketing funnels, supply chains, financial data, or data pipelines, Sankey diagrams provide a clear and intuitive way to understand movement and make better data-driven decisions.
As organizations increasingly rely on process optimization and journey analytics, Sankey diagrams continue to be one of the most valuable visualization tools in the modern analyst’s toolkit.
FAQ
What is a Sankey diagram used for?
A Sankey diagram is used to visualize how quantities move between stages, categories, or processes.
Why are Sankey diagrams popular in analytics?
They make it easy to understand flows, identify bottlenecks, and analyze transitions between stages.
Can Sankey diagrams be used for customer journey analysis?
Yes. They are widely used to visualize customer navigation paths, conversion funnels, and drop-off points.
Are Sankey diagrams available in Power BI?
Yes. Power BI supports Sankey diagrams through custom visualizations available in AppSource.
What is the main advantage of a Sankey diagram?
Its ability to clearly show the magnitude and direction of flows between multiple stages in a process.