Wind speed converter
Type a wind speed and pick its unit. Every other unit and the Beaufort force update as you type. Choose Beaufort force as the unit to see the speed range of a force instead.
- Miles per hour22.4mph
- Kilometres per hour36.0km/h
- Metres per second10.0m/s
- Knots19.4knots
- Feet per second32.8ft/s
- Beaufort force5Fresh breeze
Weather safety: forecast wind speeds are averages; gusts can be much stronger. Check your weather service's warnings before sailing, flying a drone or heading onto high ground.
How the conversions work
Every unit is converted through metres per second with the factors in NIST Special Publication 811: a knot is one nautical mile (1,852 m) per hour, about 0.514 m/s; a mile per hour is exactly 0.447 04 m/s; a foot per second is exactly 0.3048 m/s; and a kilometre per hour is 1/3.6 m/s. So 10 m/s is 36 km/h, about 22.4 mph or 19.4 knots.
The Beaufort force comes from the Met Office table: the speed is rounded to the nearest whole knot and matched to its band. Choose Beaufort force as the unit and the calculator shows each force's range in every unit instead, worked out from half a knot below to half a knot above its knot limits.
Which unit to use
Knots are the standard at sea and in aviation, while land forecasts use mph, km/h or m/s depending on the country. Pick the number of decimal places you need; the copied text keeps the same rounding, and your choice of unit is remembered for next time.
Sources
- NIST Special Publication 811, Appendix B.9: conversion factors (velocity).
- Met Office. Beaufort wind force scale.
Questions
How do I convert knots to mph quickly?
Multiply by about 1.15, as the Met Office suggests; for m/s, multiply knots by about 0.514. The converter uses the exact factors.
Why does 1 mph not equal exactly 1.6 km/h?
A mile is exactly 1.609344 km, so 1 mph is 1.609344 km/h. Rounding to 1.6 is fine for a quick estimate but drifts at higher speeds.
Can I enter a decimal Beaufort force?
No. The scale only has whole forces from 0 to 12. Enter a whole number, or switch to a speed unit to find the force for an exact speed.