Sankey Diagram: Definition, Examples & How It Works

By PPCexpo Content Team

Your Sankey Diagram should speak. If it doesn’t, don’t present it. You walk into the meeting. No small talk. No buildup. You share one slide. It’s a Sankey Diagram. The room goes quiet. Everyone gets it. Done well, a Sankey Diagram decides before anyone speaks.

That’s the power of a Sankey Diagram. It shows the flow. Where resources move. Where things stall. Where things work. The wide lines pull the eye. The structure tells the story. It does the talking for you.

But most diagrams fail. They confuse. They overload. They hide key paths. A Sankey Diagram can fix that—if built right. It must guide attention. It must earn trust. It must hold up when questions hit hard.

This guide shows how. The structure, the flow, the decisions—it all starts here.

What is a Sankey Diagram?

Definition: A Sankey Diagram shows how something moves from sources to destinations, with the link width scaled to the amount. Compared with a basic bar or line chart, it keeps the context of the journey, not just the totals.

People also call the visualization a Sankey Chart or a Sankey Plot, depending on the tool. It works best when flows split, merge, or drop off, and the audience needs to see the big picture fast. The thick bands are the point: they make relative magnitude hard to argue with.

History of Sankey Diagrams

Sankey Diagrams trace back to 1898, when engineer Matthew Henry Phineas Riall Sankey published an efficiency diagram for steam engines. The idea caught on because it made waste visible without pages of math.

Earlier flow visuals existed, but Sankey’s proportional links were the breakthrough. Over time, the term Sankey Graph showed up in engineering and energy reporting, while modern BI tools brought the format to product analytics and finance. With interactive dashboards, hovering and filtering replaced the old paper labels. And yes, the name stuck.

Key Components of a Sankey Diagram

A Sankey Plot is only as good as its building blocks and the data feeding them.

Get these right, and the story reads itself on a dashboard or in a slide.

• Nodes: the categories at each stage (Source, Step, Destination).
• Links/Flows: the connectors that carry the values between nodes.
• Magnitude: the numeric value that drives each link’s thickness.
• Labels: clear names and units so nobody guesses what “Other” means.
• Color/grouping: consistent colors that support the narrative, not a rainbow.

Utilizing the Microsoft Excel Tool to Generate Professional Sankey Diagrams

1. Open your Excel application.
2. Install the ChartExpo Add-in for Excel from Microsoft AppSource to create interactive visualizations.
3. Select the Sankey Diagram from the list of charts.
4. Select your data.
5. Click on the “Create Chart from Selection” button.
6. Customize your chart properties to add headers, axes, legends, and other required information.
7. Export your chart and share it with your audience.

The following video will help you create a Sankey Diagram in Microsoft Excel.

Utilizing the Google Sheets Tool to Generate Professional Sankey Diagrams

1. Open your Google Sheets application.
2. Install ChartExpo Add-on for Google Sheets from Google Workspace Marketplace.
3. Select the Sankey Diagram from the list of charts.
4. Fill in the necessary fields
5. Click on the Create Chart button.
6. Customize your chart properties to add headers, axes, legends, and other required information.
7. Export your chart and share it with your audience.

The following video will help you create a Sankey Diagram in Google Sheets.

Utilizing the Power BI Tool to Generate Professional Sankey Diagrams

1. Open your Power BI Desktop or Web.
2. From the Power BI Visualizations pane, expand the three dots at the bottom and select “Get more visuals.”
3. Search for “Sankey Diagram by ChartExpo” on the AppSource
4. Add the custom visual
5. Select your data and configure the chart settings to create the chart
6. Customize your chart properties to add headers, axes, legends, and other required information.
7. Share the chart with your audience.

The following video will help you create a Sankey Diagram in Microsoft Power BI.

When Should You Use a Sankey Diagram?

Use this visualization when the question is about movement through stages and the size of each route.

It’s especially useful in reviews where people argue about “big” and “small” without numbers in one view, clearly.

• One source splits into many destinations, like marketing spend by channel and downstream conversion.
• Many sources merge into one, like ingredients feeding a single finished product line.
• Drop-off matters, such as onboarding flows where users disappear between steps.
• You must compare relative magnitude across paths, without forcing a ranked list.
• The audience needs a single-page view of a multi-stage system, not ten separate charts.

Why Use a Sankey Diagram?

Use this visualization when the goal is alignment across teams, not just another KPI screenshot.

It turns debate into a concrete picture of flow, trade-offs, and loss in one glance.

• Shows contributors and losses in the same frame, so waste stops hiding inside category totals.
• Surfaces dominant paths quickly, which speeds up prioritization discussions in planning meetings.
• Helps spot bottlenecks and weird detours that would stay buried in a pivot table.
• Supports storytelling in exec decks because the visual implies cause and effect without extra narration.
• Handles multi-stage journeys better than a single Stacked Bar Chart or a simple funnel.

Types of Sankey Diagrams

Different data shapes call for different layouts, and forcing the wrong one in production dashboards gets ugly fast.

Pick the simplest type that answers the question, then add complexity only when it earns its keep visually. Some libraries label the output a Sankey Graph.

• Basic: a single left-to-right view for one source and a handful of destinations.
• Multi-level: several stages, like Source to Channel to Outcome to Region, with careful ordering to keep crossings down.
• Circular: loops back to earlier nodes, useful for recycling, returns, or manufacturing rework.
• Interactive/animated: built for filtering, hover details, and time sliders when the static view is too dense.

How to Read a Sankey Diagram?

Reading a Sankey Diagram is about following the thickness, not chasing every label at once.

Start broad, then drill into the paths that dominate the picture and drive decisions.

• Identify sources and destinations first, then confirm the unit (kWh, dollars, users) in the legend.
• Follow the thickest paths; they usually explain most of the outcome and most of the cost.
• Observe where flows split or merge, since that’s where trade-offs and segmentation show up.
• Note losses or leakages between stages, especially in energy, inventory, or conversion work.
• If it’s an interactive Sankey Chart, use tooltips or hover details to verify exact values before arguing.

Common Uses of Sankey Diagrams

This format shows up anywhere a process has forks, merges, or waste that needs a name and a number.

It’s a practical choice when stakeholders want both story and proportion on the same page.

• Energy management: generation to transmission to end-use, including losses and conversion inefficiency.
• Material flow analysis: inputs to outputs, scrap, and rework loops in a single view.
• User journey mapping: acquisition to activation to retention, with drop-off between steps that hurts growth.
• Budget/cost breakdown: funding sources to departments to programs, so “where the money went” is visible.
• Supply chain analysis: suppliers to plants to distribution centers to customers, including backorders or returns.

Advantages of Sankey Diagrams

The main advantage is proportional clarity: the viewer sees what matters first, often within 5 seconds.

That makes it strong for monthly business reviews, postmortems, and executive readouts, especially when time is tight.

• Intuitive flow representation that reads left-to-right, so audiences don’t need a training session.
• Identifies patterns and bottlenecks fast, which helps teams agree on the next experiment or fix.
• Shows complex systems in one view, reducing the urge to open ten tabs and compare screenshots.
• Highlights contributors and losses, so the biggest drivers are hard to ignore or hand-wave away.
• Supports multi-level analysis while keeping the narrative intact across stages.

Sankey Diagram vs. Other Flow Diagrams

Criteria	Sankey Diagram	Flow Chart	Alluvial Diagram	Chord Diagram
Purpose	Show quantified flow and loss	Show logic and decision paths	Show category shifts over stages	Show relationships between groups
Flow magnitude representation	Link width encodes value	Usually none	Bandwidth encodes value	Arc thickness encodes value
Best use case	Multi-stage allocations and drop-off	Process documentation and rules	Cohorts moving between states	Dense many-to-many connections
Complexity level	Medium; needs clean data	Low; easy to draw	Medium; ordering matters	High can overwhelm fast

Alternatives to a Sankey Diagram

Sometimes the flow view is the wrong tool, even if it looks impressive. If the audience needs precise comparisons, thickness can distract.

When an online Sankey Diagram feels like overkill, these options can be clearer.

• Flow Charts: best for decision logic, approvals, and step-by-step process ownership.
• Alluvial Diagrams: great for showing how categories change over time, like plan tier migrations.
• Chord Diagrams: useful for many-to-many relationships, but only with a small number of groups.
• Tree Diagrams: better for hierarchies, such as org structure or product taxonomy.
• Stacked Bar Charts: strong for comparing composition across a few categories with exact totals.

Best Practices to Create a Sankey Diagram

A strong Sankey Diagram depends on clean inputs and a layout that emphasizes flow over decoration. When done right, the visual explains movement and proportion without extra explanation.

• Prepare data: Use a simple source–target–value structure so link thickness reflects real magnitude
• Limit complexity: Keep stages and connections manageable to avoid clutter and visual confusion
• Label clearly: Add readable node names and consistent units so the meaning is never ambiguous
• Use color purposefully: Apply colors to group related flows, not to highlight every link
• Optimize layout: Order nodes logically from start to end to reduce crossings and improve flow

Common Mistakes to Avoid in Sankey Charts

A Sankey Chart can go from helpful to hopeless with a few bad choices, and a messy Sankey Graph is the usual culprit in executive decks.

Most failures come from trying to show everything at once, with no editing.

• Spaghetti effect: too many links crossing, so the eye can’t follow any single path.
• Overuse of colors and fonts: the legend turns into a puzzle and slows the reader down.
• Illogical node ordering: sources and destinations jump around, increasing crossings for no reason.
• Missing labels or context: no units, no timeframe, and no definition of “Other”.
• Node bloat: every minor category gets a node instead of being rolled up sensibly.

Basic Requirements for Creating a Sankey Diagram

The hard part is not drawing the bands first; it’s getting the data clean.

Start with a tidy link table, validate the totals, then worry about styling.

• Clear source and destination categories for every row of flow data.
• Accurate flow values with consistent units and sensible rounding rules.
• Consistent labeling, including how “Unknown” and “Other” are defined.
• Logical structure and ordering so links cross as little as possible.
• A validation check that totals reconcile across stages when they should.

Sankey Chart Dataset Example

Source	Target	Value	Unit	Notes
Paid Search	Landing Page	12000	Users	January cohort, tagged via UTM parameters
Organic Search	Landing Page	18000	Users	Search console sessions, same date range
Landing Page	Bounced	21000	Users	Exit after one page, session length under 10 seconds
Landing Page	Sign Up	9000	Users	Simple Sankey Plot example for a signup funnel
Sign Up	Activated	4200	Users	Activation is defined as the first key action within 7 days
Activated	Retained 30d	2100	Users	Retention cohort at 30 days, excluding reactivations

Sankey Diagram Features

Feature	Description	Why it matters
Proportional Links	Link width scales to the numeric measure	Makes dominant routes obvious at a glance
Node Grouping	Rolls minor categories into “Other” using a threshold	Reduces clutter and prevents spaghetti crossings
Sorting and Ordering	Controls node sequence by stage and business logic	Improves readability and supports a clean story
Interactive Tooltips	Shows exact values, percent of total, and metadata on hover	Supports QA and reduces meeting arguments
Highlighting	Emphasizes one segment or path with filtering or focus	Good for guided walkthroughs in dashboards

FAQs

What software can I use to create a Sankey Diagram?

Excel, Google Sheets, Power BI, Tableau, and Python libraries can build this flow visual. For quick exploration, a Sankey Diagram generator in the browser is convenient. For governed reporting, keep it in the platform that owns the model and refresh.

What does a Sankey Diagram show?

It shows how a measured quantity moves between stages, with thicker links meaning larger amounts. The value is context: totals and the paths that created them. Use it to spot where volume concentrates and where it leaks away.

What is the most famous Sankey Diagram?

Minard’s map of Napoleon’s 1812 campaign is the reference people cite most. While it mixes geography with flow, it’s still a Sankey Diagram example of magnitude and loss. Early steam engine efficiency charts from the late 1800s are also classics.

What is the difference between a Sankey Diagram and a Flow Chart?

A Flow Chart explains logic: steps, decisions, and what happens next. This flow visualization explains magnitude: how much moves along each path. Use a Flow Chart for rules and exception paths; use the flow view for volume and loss.

Wrap-up

If your chart doesn’t pass in eight seconds, it won’t pass in a meeting. That’s the first rule. It should explain itself. No point. No talking. No guesswork.

Start from the end. Work backward. Map every flow to the choice that matters. This flips the usual way of building. It also sharpens your thinking. You’re not showing data. You’re showing cause and effect.

A strong chart shows where things slow down. It spots what others miss. Clean visuals can lie. Clarity means showing the jam, not hiding it behind neat lines.

Use contrast to guide the eye. Keep the important nodes up front. Make sure your flow order matches how people think. If your layout feels off, people won’t trust what they’re seeing.

Static tools break under pressure. So does poor structure. Use the right tool. Test before exporting. A graph that freezes mid-pitch takes your credibility with it.

Interactive mode helps you recover in real time. One checkbox gives you room to adjust, highlight, or zoom as questions come in. That keeps control in your hands.

If you see nine questions in ninety seconds, your node logic failed. That’s not a flow. That’s a knot. Connect things the way the audience expects. Make every connection earn its place.

Not every meeting needs a chart. But if you’re going to show one, make it count. Know when to delete. Know when to redraw.