Knots to Kilometers per Hour

Unlike most speed conversions, this one has no long decimal tail. The nautical mile was fixed at exactly 1,852 m by the International Hydrographic Conference of 1929, so a knot is exactly 1.852 km/h and about 0.514 m/s. That figure was chosen because it is close to the average length of one minute of latitude, which is why navigators can measure distance straight off the latitude scale of a chart.

The meter has been defined since 1983 as the distance light travels in 1/299,792,458 of a second, and the knot inherits that precision through the nautical mile.

Marine and aviation weather is reported in knots even in metric countries, while the public forecast may use km/h, so sailors and pilots convert all the time. On the Beaufort scale, force 6, a strong breeze, is 22 to 27 kn, about 41 to 50 km/h; force 8, a gale, is 34 to 40 kn, 63 to 74 km/h; and hurricane force 12 starts at 64 kn, about 119 km/h. Airport weather reports, known as METARs, give wind as, for example, 27015KT: from 270 degrees at 15 kn, which is 27.8 km/h.

Ships follow the same pattern. A harbor speed limit of 5 kn is 9.3 km/h, a cruising sailboat at 7 kn makes about 13 km/h, and a large container ship at 22 kn moves at 40.7 km/h. Airliners cruise at roughly 450 to 490 kn true airspeed, around 830 to 910 km/h.

Do not use the road-mile factor of 1.609 here; that answers a different question and understates the speed by more than 13%. Also check whether a wind figure is in knots, km/h or m/s: many European and Asian weather services publish m/s, where 10 m/s is 19.4 kn and 36 km/h.

For US speeds use knots to mph; for m/s readings try meters per second to km/h. All speed units are in the unit converter.