Kilometres per hour (km/h) to Knot (kn)
To convert kilometres per hour to knots, multiply by 0.5400. One knot equals exactly 1.852 km/h — a nautical mile per hour. Knots are the standard unit of speed in aviation, shipping, and maritime weather forecasts worldwide. In the UK, BBC shipping forecasts and the Met Office use knots for wind speed at sea, while road speeds and everyday weather reports use miles per hour.
Frequently asked questions
30 km/h × 0.5400 = 16.2 knots. This is a moderate breeze — around Force 4–5 on the Beaufort scale — enough to give a sailing dinghy a lively ride.
Knots are tied directly to the nautical mile, which is based on one arcminute of latitude on the Earth's surface. This makes navigational calculations far simpler at sea and in the air, where positions are expressed in degrees, minutes, and seconds. International conventions for both maritime and aviation navigation mandate the use of knots.
The UK Met Office issues a gale warning when mean winds are expected to reach Force 8 (34–40 knots, or approximately 63–74 km/h) or when gusts are forecast to exceed 43 knots (80 km/h). Force 9 (41–47 knots) is classified as a severe gale.
BBC weather reports for the general public use miles per hour for wind speed. However, the BBC Radio 4 Shipping Forecast — broadcast four times daily and vital for mariners — uses knots throughout, following international maritime convention. The Met Office's marine forecasts also use knots.