Beaufort Wind Scale Calculator
The Beaufort Wind Scale Calculator turns a measured wind speed into the classic 0–12 Beaufort force number and its plain-language description, from Calm to Hurricane force. Enter a speed in km/h and it also reports the equivalent in knots and metres per second so you can cross-check forecasts, marine warnings and field observations.
Enter Values
How to use this calculator
- Enter the wind speed in kilometres per hour (km/h).
- Read the Beaufort force number (0–12) and its description.
- Use the knots and m/s values to match marine or scientific reports.
How it works
Wind speed is converted to metres per second (km/h ÷ 3.6), then the Beaufort force is estimated with B = round((v ÷ 0.836)^(2/3)) and clamped to the 0–12 range. The force number is mapped to its standard description via a fixed lookup (0 Calm through 12 Hurricane force). Knots are found by dividing km/h by 1.852.
Worked example
Worked example. A 40 km/h wind is 11.111 m/s. B = round((11.111 ÷ 0.836)^(2/3)) = 6, a Strong breeze, which is about 21.6 knots.
Common mistakes
- Entering the speed in knots or mph instead of km/h — convert first.
- Treating the force number as an exact cutoff; the scale is a descriptive band.
- Assuming gust speed equals the sustained wind the scale describes.
Frequently asked questions
What wind speed is a gale?
A gale is Beaufort force 8, roughly 62–74 km/h sustained wind.
Does the calculator use gusts or sustained wind?
The Beaufort scale describes sustained wind. Enter the average wind speed, not a short gust, for a representative force.
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Explore more in Weather & Environmental Monitoring.
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.