What is a knot, and where did it come from?
A nautical mile per hour, measured by counting knots in a rope.
A knot is a speed of one nautical mile per hour. The name comes from an old sailing trick: a chip log — a wooden board tied to a long rope with knots tied at fixed intervals — was tossed overboard. Sailors counted how many knots played out in 30 seconds, and the count gave speed in nautical miles per hour.
A nautical mile is 1,852 metres (originally one minute of latitude along any meridian). That makes it convenient for navigation: 1 knot ≈ 1 minute of latitude per hour, and you can read your position directly off a chart.
Today, knots are used for:
- Marine navigation — boats, ships, sea state forecasts. - Aviation — air traffic control, flight plans. Most airlines display airspeed in knots on the cockpit displays, even though passengers see km/h on the seat-back screen.
Converting knots to mph: 1 kn = 1.15078 mph. To km/h: 1 kn = 1.852 km/h. To m/s: 1 kn = 0.5144 m/s. The conversion page (knot to mph) gives instant values across 6 units.