A Sankey diagram visualizes flow — how quantities move between stages, categories, or states. The width of each flow band is proportional to the quantity it represents. One glance shows where volume concentrates and where it dissipates.
How to make a Sankey diagram
Format your flow data
Open the Sankey diagram maker and enter your flows as source → target → value triplets, one per line. Example: Website → Sign-up → 1200
Arrange and label nodes
Each unique name becomes a node. The tool auto-arranges nodes into columns by flow direction. Add a title that describes what the flows represent.
Download your diagram
Save the chart as PNG or PDF.
Anatomy of a Sankey diagram
- Node — a box representing a stage, category, or state (e.g., "Website Traffic", "Paid Search", "Checkout")
- Link / flow — a curved band connecting two nodes. Its width encodes the quantity flowing from source to target.
- Source — the origin node that a flow leaves from
- Target — the destination node that a flow arrives at
- Value — the quantity of the flow (visitors, dollars, energy units, etc.)
What Sankey diagrams reveal
The power of Sankey is showing where things go. In a user funnel, you see exactly how many users drop off at each stage. In an energy flow, you see which conversion step wastes the most. The widest flows carry the most volume — the eye goes there first.
A thin band becoming thinner signals loss. A thick band splitting into many smaller ones shows diversification. These patterns are invisible in tables and hard to read in bar charts.
Good Sankey data formats
| Use case | Source | Target | Value |
|---|---|---|---|
| Website funnel | Visit | Sign-up | 5400 |
| Website funnel | Visit | Bounce | 3200 |
| Energy balance | Coal | Electricity | 820 |
| Budget flow | Revenue | Salaries | 430000 |
Each row is one flow. A node can appear as both a source (output flows) and a target (input flows).
Ready-to-paste example datasets
Website conversion funnel
Visitors,Sign-up page,5400
Visitors,Bounce,3200
Sign-up page,Registered,2100
Sign-up page,Abandoned,3300
Registered,Active user,1400
Registered,Churned,700
Energy balance (simplified UK power grid)
Coal,Electricity,820
Gas,Electricity,1240
Nuclear,Electricity,600
Renewables,Electricity,540
Electricity,Industry,1100
Electricity,Homes,850
Electricity,Transport,320
Electricity,Losses,930
Annual budget allocation
Revenue,Salaries,430000
Revenue,Infrastructure,180000
Revenue,Marketing,95000
Revenue,R&D,120000
Revenue,Operations,75000
Revenue,Net profit,100000
Each row is Source,Target,Value. Paste it directly into the data panel — the tool auto-builds the node layout.
When to use a Sankey diagram
- User or customer funnel (traffic → leads → conversions)
- Energy or material flow analysis
- Budget allocation (where does revenue go?)
- Migration between categories (which features do users switch from/to?)
- Any "from → to" story where quantity matters
- Flows that cycle or loop back — Sankey diagrams are acyclic (one direction)
- More than ~15 nodes — the diagram becomes unreadable spaghetti
- When you only have totals per category with no flow direction — use a bar chart
Sankey vs flowchart
Both show connections between steps, but they're fundamentally different:
| Sankey diagram | Flowchart | |
|---|---|---|
| Encodes quantity | Yes (band width) | No |
| Shows process logic | No | Yes (decisions, conditions) |
| Good for volume analysis | Yes | No |
| Directional | Yes | Yes |
A flowchart shows how a process works. A Sankey shows how much flows through it.
FAQ
Can flows split and merge?
Yes — one node can receive flows from multiple sources and send flows to multiple targets. This is what makes Sankey diagrams useful for complex flow networks.
What units should I use for values?
Any consistent unit works: visitors, dollars, kilowatts, tons. The diagram shows proportional width, so what matters is that all values use the same unit so the widths are comparable.
My flows don't balance — is that okay?
Not always. In a conservation system (energy, budget), total inputs should equal total outputs. In a funnel (website traffic), it's normal for totals to decrease at each stage — that's the drop-off you're visualizing.
How many nodes is too many?
More than 10–15 nodes usually produces an unreadable diagram. If you have many small flows, group minor categories into an "Other" node to keep the diagram clean.
How this guide is reviewed
This guide is maintained by the ChartsMakers Editorial Team and reviewed for statistical accuracy, product behavior, and clarity. When a guide relies on software behavior or statistical definitions, we check it against official documentation or established references. See our editorial policy.