Sankey Diagram vs Flowchart: Which One to Use
A flowchart shows the steps and decisions of a process; a Sankey diagram shows how much moves along each route. Learn the difference and which one answers your question.
A flowchart shows what happens and in what order. A Sankey diagram shows how much of something moves along each path.
Both draw boxes connected by arrows, which is why they get confused. The difference is what the connections mean. In a flowchart an arrow means "then" or "if yes"; in a Sankey a band means "this much".
The example is an order process drawn as a Sankey: of 500 orders, 450 are shipped and 50 cancelled, and 430 of the shipped are delivered while 20 come back. A flowchart of the same process would show the steps and the decisions, not the quantities.
The difference in one table
A flowchart answers: what are the steps, who does them, and what are the decisions? A Sankey diagram answers: how much goes where, and what is lost?
- Arrows: sequence and logic in a flowchart; quantity in a Sankey.
- Width: constant in a flowchart; proportional to the amount in a Sankey.
- Decisions: first-class in a flowchart; not shown in a Sankey, only their outcome.
- Best for: documenting and improving a process, against understanding volume and loss.
Which one to choose
Ask what the reader needs to decide. If it is how the work is done, who owns each step, or where a rule applies, draw a flowchart, or a swimlane diagram when responsibility matters. If it is where the volume goes and where it leaks, draw a Sankey.
They work together: the flowchart documents the process, and a Sankey of the same process shows how many cases take each path.
Key points
- 500 orders enter; 430 are delivered, so 86% complete in this example.
- A flowchart of this process would show the shipping decision; the Sankey shows that 10% of orders are cancelled before it.
- Neither chart replaces the other.
- The figures are invented.
The example’s data
Invented order counts for one period, balanced at every node.
| From | To | Amount (orders) |
|---|---|---|
| Orders | Shipped | 450 |
| Orders | Cancelled | 50 |
| Shipped | Delivered | 430 |
| Shipped | Returned | 20 |
The same data as CSV
source,target,value
Orders,Shipped,450
Orders,Cancelled,50
Shipped,Delivered,430
Shipped,Returned,20How it works
State the question
Write down what the reader should be able to answer after seeing the diagram.
Pick the chart that answers it
Sequence and decisions: flowchart. Responsibility: swimlane. Quantity moving between stages: Sankey.
Combine them if you need both
Document the process as a flowchart and add a Sankey for its volumes.
Frequently asked questions
Can a Sankey diagram show decisions?
It can show the result of a decision as a split, but not the rule behind it. For the rule, use a flowchart.
Can I turn a flowchart into a Sankey diagram?
Only if you have a quantity for each path. The steps become nodes and each connection needs an amount.
Edit this order Sankey
Open the example as your own chart and add the volumes from your own process.