Beaufort Wind Speed Calculator
The Beaufort scale ranks wind force from 0 to 12. Each force maps to a published band of wind speeds and a descriptive sea state used in marine forecasts. This calculator takes a Beaufort number and returns a representative wind speed in knots, miles per hour, and metres per second using the standard empirical formula, alongside the official knot range and description for that force.
Beaufort wind speed formula
v (m/s) = 0.836 * Beaufort^1.5
knots = m/s / 0.514444
mph = m/s * 2.236936
The formula gives a representative mean wind speed at the 10 metre reference height for each force. The published knot range comes from the standard Beaufort table.
Beaufort scale summary
- Force 0: calm, under 1 knot.
- Force 4: moderate breeze, 11 to 16 knots.
- Force 6: strong breeze, 22 to 27 knots.
- Force 8: gale, 34 to 40 knots.
- Force 12: hurricane force, 64 knots and above.
Beaufort scale: frequently asked questions
How do you convert Beaufort force to wind speed?
The empirical relationship is v = 0.836 * B raised to the power 1.5 metres per second, where B is the Beaufort number. This gives the representative mid-band 10-metre wind speed for each force. Force 6, for example, gives about 12.29 m/s, roughly 24 knots, which sits in the published 22 to 27 knot band.
What is the Beaufort scale?
The Beaufort scale is a measure of wind force from 0 (calm) to 12 (hurricane force), originally based on observable effects on the sea and land. Each force corresponds to a published range of wind speeds and a descriptive sea state, standardised internationally for marine forecasts.
Why does the calculator show a speed range as well as a value?
Each Beaufort force covers a band of wind speeds, not a single value. The formula returns a representative speed within that band, and the calculator also shows the published lower and upper knot limits for the force so you can see the full range.
Is the wind speed measured at a standard height?
Yes. Beaufort wind speeds refer to the wind at the standard 10 metre reference height over open water. Wind at the surface or in gusts can differ from this mean value.
Official sources
- NOAA National Weather Service: Beaufort Wind Scale.
- NIST: unit conversions (knot, mph, m/s).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.