Convert wind speed between knots, km/h, mph and m/s, and read where it sits on the Beaufort scale. Enter a Beaufort force to see the speed range for it.
Wind Speed Converter
Convert wind speed between knots, km/h, mph and m/s, and read it on the Beaufort scale.
- Knots 15.0 kn
- Kilometres per hour 27.8 km/h
- Miles per hour 17.3 mph
- Metres per second 7.7 m/s
Beaufort force
Moderate breeze
Small waves growing longer; frequent whitecaps.
How it works
Knots, km/h, mph and m/s are just different units for the same speed, so converting between them is exact.
1 knot = 1.852 km/h = 1.151 mph = 0.514 m/s
The Beaufort scale is different: it maps ranges of wind speed to a numbered force with a described sea state, from Force 0 (calm) to Force 12 (hurricane force). Pick “Beaufort force” as the input to see the speed range for any force.
Limitations & good practice
- Beaufort is an observational scale. Each force is a band of wind speeds tied to a described sea state, not a single exact value — treat the force as a category.
- Gusts are not the average. Forecasts and the scale describe the sustained mean wind; gusts commonly run 30–50% higher, so reef for the gusts, not the average.
- The standard is measured at 10 metres. Beaufort speeds refer to wind 10 m above the surface in the open; at deck level, in gusts, or in the lee of land the wind you feel differs.
- Range boundaries are conventions. The rounded values in each unit come from the WMO tables; a speed near a boundary can reasonably sit in either force.
Always plan against the forecast gusts and your crew and boat limits, and read the local marine forecast rather than any single converted number.