Variables ranked by impact on an outcome. Bars extend left/right of a central baseline.
A free, animated tornado (sensitivity) chart you can read here or embed on any website, from Scrollchart.
Tornado (Sensitivity) Chart
A tornado chart ranks the input variables of a model by their impact on an output metric. Each row is one variable. The central vertical line represents the baseline value of the output (the model result when all inputs are at their expected values). For each variable, two bars grow outward: the left bar shows how far the output falls when that variable is at its low case, and the right bar shows how far the output rises at the high case. Variables are sorted from largest total span at the top to smallest at the bottom, creating the wide-to-narrow tornado shape.
The format is a standard output of one-at-a-time sensitivity analysis in financial modelling, project risk assessment, and engineering design studies.
The topmost variable has the most leverage on the outcome: changing it from low to high produces the widest swing. Variables near the bottom are relatively insensitive and can often be held at their expected values without materially affecting the result. Focus analytical effort and risk management on the top three to four variables.
The left-right asymmetry within a single row matters too. A bar that extends much further left than right means the downside risk from that variable is larger than the upside opportunity. A bar that extends equally in both directions means the variable has symmetric impact. When multiple variables have asymmetric exposure in the same direction, the total distribution of outcomes is skewed accordingly.
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Source & accuracy
This tornado (sensitivity) chart is an editorial illustration built to represent the concept accurately. Where it shows figures, they are typical or representative values chosen to make the relationship clear, not a single underlying dataset. The diagram and its explainer are reviewed and maintained centrally, and updated over time as understanding improves.
Ranking inputs by their outcome impact
A tornado sensitivity chart ranks variables by how much they influence an outcome. Each variable is assigned a bar. The bar's length shows the range of the outcome when that variable moves from its low to high value, holding all others constant. The tallest bar represents the variable with the most leverage. The bars are sorted descending by length, and the staggered outline resembles a tornado, hence the name. This is the standard tool for identifying which assumptions drive uncertainty in financial models, risk assessments, and engineering designs.
Building and interpreting sensitivity rankings
To build a tornado chart, vary each input across its plausible range and measure the resulting change in output. Variables that produce wide outcome swings are highly sensitive. Variables with little impact can be held constant or estimated crudely. The chart guides where to invest: if doubling Variable A changes the output by 5% but doubling Variable B changes it by 50%, reducing uncertainty in B has much higher value. Tornado charts also expose model structure: if one variable towers over all others, the model is brittle to that assumption.
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Reference
What this is
A free, embeddable, animated tornado (sensitivity) chart for any website.
Who uses it
Data journalists, Researchers & academics, Content marketers, News organizations.
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License
Free forever. Editorial explainer text included; updated centrally over time.
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Frequently asked questions
Where can I get a free animated "Tornado (Sensitivity) Chart" for my website?
Scrollchart provides "Tornado (Sensitivity) Chart" as a free, embeddable animated diagram you can add to any website with one line of HTML. No signup is required and there is no watermark. The diagram and its explainer text are served from scrollchart.com, so the embed stays current without any maintenance on your end.
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