Sankey chart vs Sankey diagram: is there a difference?
No. Sankey chart, Sankey diagram and Sankey graph all name the same picture: bands whose widths show how an amount splits and flows from one place to another. The words differ by habit, not by meaning. There is one neighbouring chart that does differ, though, and it is worth knowing which one.
Where the names come from
The form is named after Matthew Henry Phineas Riall Sankey, an Irish engineer who in 1898 drew the energy efficiency of a steam engine as a band that narrowed as heat was lost. Engineers called such drawings diagrams, and "Sankey diagram" remains the term in engineering, energy and sustainability writing.
Business and data-visualization tools adopted the form later and filed it with their other charts, so "Sankey chart" is common in dashboards, spreadsheets and BI software. "Sankey graph" is a rarer third spelling of the same idea.
Which name to use
Use the word your readers use. An energy report says diagram; a marketing dashboard says chart. Search engines treat the two as the same query, and so does every tool that draws one.
The one that is different: alluvial diagrams
An alluvial diagram looks similar but answers a different question. A Sankey shows how an amount splits and merges as it flows through nodes; an alluvial diagram shows how the same set of items is grouped differently across several fixed categories or points in time. When the columns are moments rather than steps, you are usually looking at an alluvial diagram.
Frequently asked questions
Is a Sankey chart the same as a Sankey diagram?
Yes. Both names describe the same visualization: bands whose widths are proportional to the amounts flowing between nodes. Diagram is the older, engineering term; chart is common in business tools.
Who invented the Sankey diagram?
It is named after Captain Matthew H. P. R. Sankey, who used one in 1898 to show the energy efficiency of a steam engine.
Try it on your own numbers
The editor is free and opens with a starter Sankey diagram. One row per node, and the diagram draws itself as you type. No signup required.
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