When should I use a Sankey diagram instead of a bar chart or pie chart?

Reach for a Sankey diagram whenever you need to show how quantities move, branch, or converge across multiple stages. Bar charts compare independent values side by side, and pie charts partition a single total, but neither one shows directionality or multi-hop transfers. Sankey diagrams are the right choice for energy audits, budget routing, material-flow tracking, and any process where understanding the path and volume of transfers is more informative than a simple before-and-after comparison.

How do I read a Sankey diagram?

Nodes, shown as labeled rectangles or text anchors, represent stages or categories in the system. The ribbons that link them carry quantities, and ribbon width is always proportional to the amount being transferred. Trace a ribbon from left to right (or top to bottom) to follow how a given input is distributed. Thicker ribbons signal dominant pathways; thin ribbons reveal minor flows. Where a ribbon splits, look at the relative widths of the branches to understand how the quantity is partitioned.

Can I use Sankey diagrams in academic research papers?

Yes. Sankey diagrams appear regularly in peer-reviewed journals across energy research, environmental science, clinical medicine, and economics. They are particularly standard in life-cycle assessments, industrial ecology studies, and CONSORT participant-flow reports for clinical trials. The scientific publication style in Figviz produces clearly labeled, unit-annotated diagrams formatted to the standards expected by most journal editors.

How many nodes and flows should a Sankey diagram have?

Most readers can comfortably parse diagrams with 5 to 15 nodes and up to about 20 to 25 flow bands. Beyond that threshold, crossing ribbons and dense labeling start to obscure the main story. When your dataset has many small contributors, consolidate them under a single grouped node such as "Other" or "Miscellaneous." Figviz automatically optimizes node placement and ribbon routing to keep the result legible regardless of how you phrase your description.

What data do I need to create a Sankey diagram?

At a minimum you need source-target pairs with associated quantities, for example "coal combustion to steam: 88 units; coal combustion to ash: 12 units." You can also write a plain-language description of your process and the AI will infer plausible proportions from the context. For precise scientific or engineering work, supply your actual measured values so the ribbon widths faithfully represent your data.

For Science & Engineering

Sankey Diagram Generator AI-Powered

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✓Proportional Flow Widths✓Multiple Flow Types✓Publication-Ready Quality✓Scientific & Modern Styles

Sankey Diagram Examples

Explore scientific and engineering samples below, or build your own with the generator above

Energy Flow in Ecosystem

Trophic energy-flow diagram showing how photosynthetic input diminishes at each feeding level, from primary producers all the way up to apex predators.

ecologyenergy-flowtrophic-levels

Research Funding Allocation

Grant-distribution diagram illustrating the path of research dollars from sponsoring agencies through institutional departments to tangible research deliverables.

fundingresearchallocation

Material Flow Analysis

Manufacturing mass-balance diagram that follows input materials through each production stage and accounts for every output, including reusable scrap and disposal streams.

industrialmaterial-flowmanufacturing

Patient Flow in Clinical Study

Trial participant-flow diagram tracking how study volunteers progress from eligibility screening through blinded treatment arms to each measured endpoint.

clinical-trialpatient-flowmedical

Carbon Emissions Flow

Greenhouse-gas pathway diagram connecting emission-producing sectors to atmospheric accumulation and quantifying how much carbon is absorbed by oceans, land, and capture systems.

carbonemissionsclimate

Supply Chain Resource Flow

End-to-end supply chain diagram revealing how product volume moves across procurement, fulfillment, and retail touchpoints before reaching buyers and recycling streams.

supply-chainlogisticsresources

Prompt templates you can copy

Start with one of these examples, then adapt the subject, labels, data, or layout for your own use.

Energy Flow in Ecosystem

Trophic energy-flow diagram showing how photosynthetic input diminishes at each feeding level, from primary producers all the way up to apex predators.

Sankey diagram showing energy flow through an ecosystem, solar radiation flowing into primary producers (plants), then to primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers (apex predators), with heat loss branches at each level, band widths proportional to energy magnitude, green to orange color gradient, scientific illustration style, white background

Research Funding Allocation

Grant-distribution diagram illustrating the path of research dollars from sponsoring agencies through institutional departments to tangible research deliverables.

Sankey diagram showing research funding allocation, sources on left (NIH, NSF, DOE, Private Foundations) flowing through university departments (Biology, Chemistry, Physics, Engineering) to specific research outputs (publications, patents, clinical trials, datasets), band widths proportional to dollar amounts, blue and teal color palette, professional clean design, white background

Material Flow Analysis

Manufacturing mass-balance diagram that follows input materials through each production stage and accounts for every output, including reusable scrap and disposal streams.

Sankey diagram showing material flow analysis in manufacturing, raw materials (steel, plastic, aluminum, glass) flowing through processing stages (forming, assembly, finishing) to outputs (finished products, recyclable waste, landfill waste, emissions), band widths proportional to mass, industrial gray and green color scheme, technical diagram style, white background

Patient Flow in Clinical Study

Trial participant-flow diagram tracking how study volunteers progress from eligibility screening through blinded treatment arms to each measured endpoint.

Sankey diagram showing patient flow in a clinical trial, screened patients flowing through enrollment, randomization into treatment arm and placebo arm, then to outcomes (complete response, partial response, stable disease, progressive disease, dropout), band widths proportional to patient numbers, medical blue and red color scheme, clean professional style, white background

What is a Sankey Diagram?

A Sankey diagram is a type of flow chart where the thickness of each connecting band scales directly with the quantity being transferred. Captain Matthew Sankey popularized the format in 1898 when he used it to audit steam-engine efficiency, and the design has remained a cornerstone of quantitative visualization ever since. The core strength of these diagrams lies in their ability to show, at a glance, where inputs go, how they split across branches, and where significant losses occur. That makes them indispensable for energy audits, industrial mass-balance studies, budget breakdowns, and any situation where tracking the magnitude of movement between stages is as important as the movement itself.

Why Use Sankey Diagrams in Research?

Represent energy conversions and thermal losses with band widths that reflect actual magnitudes

Follow raw materials through production steps to pinpoint inefficiency and excess waste

Chart participant movement across clinical trial arms from screening to final outcomes

Trace greenhouse-gas emissions from source industries through to atmospheric accumulation

Present layered, multi-stage processes to peer reviewers and non-specialist stakeholders

Surface allocation patterns buried in spreadsheets that bar charts and tables leave invisible

Types of Sankey Diagrams

The Sankey format adapts to many domains without losing its defining proportionality rule. Energy-flow diagrams show inputs, conversions, and losses in power systems or buildings. Material flow analysis (MFA) diagrams record the mass of substances moving through extraction, use, and end-of-life stages. Budget and financial diagrams reveal how revenue is distributed across cost centers and expenditure lines. Process-flow diagrams follow entities such as patients, users, or manufactured parts through sequential decision points with branching outcomes. Each variant uses the same underlying principle that band width equals quantity, though labeling conventions, units, and color practices vary across disciplines.

How to Create Effective Sankey Diagrams

Begin by listing every input node and output node in your system, then assign a measured quantity to each connection. Aim to keep visible paths below eight major flows to prevent the diagram from becoming unreadable. Apply color with intention: a continuous gradient can guide the eye along the dominant pathway, while distinct hues help readers distinguish separate resource categories. Label every node with a name and its unit so the scale is immediately clear. Arrange nodes so flow moves in one consistent direction, and cluster related nodes to reduce crossing bands. Figviz handles these layout decisions automatically, letting you focus on describing your data rather than adjusting positions by hand.

Applications in Science and Engineering

Ecology: quantifying energy transfer through food webs and nutrient cycles across ecosystem layers

Chemical engineering: verifying mass and energy balances in reactor networks, distillation columns, and refineries

Environmental science: charting freshwater withdrawals, carbon footprints, and municipal waste routing

Healthcare: mapping care pathways, treatment response rates, and hospital resource consumption

Urban planning: analyzing commuter movement, power grid distribution, and city-wide material metabolism

Economics: depicting bilateral trade volumes, supply network structures, and national resource budgets

Frequently asked questions

Figviz provides a free AI-assisted Sankey diagram generator that produces proportional, publication-quality flow visualizations within seconds. Describe your data in plain language, choose a visual style and flow type, and the tool handles all layout and scaling automatically. No coding, spreadsheet uploads, or manual node positioning required.

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