Sankey Diagram Generator Proportional Flow, Free

Nodes and flows: how a Sankey is built

A Sankey diagram has two ingredients. Nodes are the boxes — the stages, categories, or entities (a fuel source, a department, a product line). Flows are the bands that connect one node to another, each carrying a value. The height of a node is set by its largest side: the sum of everything flowing in or the sum of everything flowing out, whichever is bigger. The thickness of a flow is set by its value. Because both use the same scale, the picture stays honest — wide bands really do carry more.

Two ways to make a Sankey diagram here

• Precise mode: type one flow per line as Source, Target, value. The tool assigns each node to a column, sizes every node and band to a single shared scale, and renders an exact diagram you can download as SVG — accurate every time, no dragging.
• AI illustration mode: describe the flow you want in plain English and the tool generates a polished, presentation-ready illustration with themed colors and styling.
• Use precise mode when the proportions must be correct (energy budgets, financial flows, reports); use AI mode when you want a styled, on-brand graphic for slides or social.

Energy, budget, and material flow diagrams

Sankey diagrams earned their name from an 1898 engineering chart of a steam engine’s energy, and energy is still where they shine: showing how primary sources convert to electricity and end uses, with losses peeling off as visible bands. The same structure fits a household or company budget — income splits into categories and sub-categories, each sized to its dollar amount. It also fits material flow analysis, where raw inputs move through processing into products, recycling, and waste. Anywhere a total divides and recombines, a Sankey makes the proportions obvious at a glance.

How to make a Sankey diagram from your data

• List your flows, one per line, in the form Source, Target, value — for example, "Coal, Electricity, 30".
• Reuse the same node name across lines to chain stages (Coal flows into Electricity; Electricity flows into Residential).
• The tool places each node in a column by its distance from a source, then sizes every node and band on one shared scale.
• Edit the title, check the proportions, and export a clean SVG to drop into a doc, slide, or report.

When to use the AI illustration mode

Reach for AI illustration mode when you want an eye-catching, styled graphic rather than a strict data layout — a themed energy or budget flow for a presentation, a blog graphic, or a social post. For anything where the band widths must be exactly right, such as a published energy balance or a financial report, use precise mode so the proportions are computed from your numbers rather than drawn by hand.