Sankey Diagram Maker

How to Use the Sankey Diagram Maker

1. 1. List the flows. Write one flow per line as Source -> Target: value. A name is one box wherever it appears, so Housing as a target and as a source is the same box.
2. 2. Chain them. A flow's target can be the source of the next, so money, energy or people can pass through several stages. Repeat lines for the same pair add up.
3. 3. Check the notices. Lines that cannot be drawn are left out with a reason: a missing value, a flow to itself, or a flow that would loop back. Boxes that take in and send out different amounts are listed too.
4. 4. Adjust the look. Choose how boxes are ordered in each column, whether ribbons take their source's or target's color, whether labels show amounts, and a unit to print after them.
5. 5. Download. Take the SVG or PNG. With APA style figure on, the figure number and title go above the image and an optional note goes below.

The Input Syntax

Values must be above zero. A decimal comma works where your keyboard uses one, but type amounts without thousands separators — a lone comma is read as the decimal mark. Up to 40 boxes and 100 flows are drawn.

How the Diagram Is Built

Each box goes in the column after the longest chain of flows that leads to it, and boxes that only receive flow are moved to the last column so every path ends at the right-hand edge. Ribbon width is the flow multiplied by one scale for the whole diagram, chosen so the fullest column fits the height. A ribbon of 500 is therefore twice as wide as a ribbon of 250, in any column. Boxes start in the order they first appear in your list, and Reduce crossings then reorders each column using the average position of the boxes it connects to. The result is the same every time for the same text.

Wages -> Household income: 3400
Benefits -> Household income: 300
Household income -> Housing: 1500
Household income -> Savings: 2200

Reading and Writing About a Sankey Diagram

Sankey diagrams are named after Captain Matthew Sankey, who used one in 1898 to show how much of a steam engine's energy was useful and how much was lost. They suit any quantity that is split and combined — energy, money, materials, people moving between stages. They are poor at comparing many small flows, because thin ribbons are hard to tell apart; the table under the image gives the exact figures, and in a paper you should say what the unit is and what period or place the data covers.

• Say what is measured. Put the unit in the title or the unit field, and the period in the title or the figure note.
• Keep flows conserved. A box that takes in 100 and sends out 80 has lost 20 somewhere; add an explicit loss flow so the diagram balances.
• Keep it readable. Past about 25 flows, group the small ones into an Other box and give the details in a table.

Frequently Asked Questions

What is a Sankey diagram?

A Sankey diagram is a flow diagram in which the width of each ribbon is proportional to the quantity it carries. Boxes (nodes) stand for stages, categories or places, and the ribbons show how much moves between them. It is used for energy, money, materials and similar flows.

How do I make a Sankey diagram from a list?

Write each flow on its own line as Source -> Target: value, for example Wages -> Income: 3400. The diagram redraws as you type. Flows whose target is another flow's source are chained into further columns automatically.

Why was a flow left out of my diagram?

The tool leaves out a line it cannot draw and tells you why: the line is not in the Source -> Target: value form, the value is missing or not above zero, a box flows to itself, or the flow would loop back to an earlier box. A Sankey diagram flows in one direction.

Why do some boxes show flow in and out that differ?

Real data often loses or gains an amount along the way — heat lost, a rounding gap, income not listed. The box is drawn as tall as the larger side, and the page lists such boxes. If you want the diagram to balance, add a flow to a Loss or Other box.

Can I choose which column a box goes in?

Not directly. A box sits one column after the longest chain of flows leading to it, and boxes with no outgoing flows go to the last column. To move a box, change the flows — for example, route it through an extra stage.

Can I put a Sankey diagram in an APA paper?

Yes, as a figure. Turn on APA style figure to set the figure number and title above the image and an optional note below. Say in the note what the units are and where the data came from, and cite the source of any data you did not collect yourself.