Speed is something that we usually measure in kilometers per hour (km / h) since we are used to traveling by car or also, it is the measure used to travel long distances by train, but in case we board a boat or sailboat we will be talking about knots, so if you want to know how much a knot is equal in kilometers, keep reading because we will explain it to you below. How much is a knot equal in kilometers? At sea, the unit of measurement of speed It is not the meter per second or the km per hour: it is the knot. This unit existed 200 years before the invention of the metric system. It was the British in the 16th century who developed a technique to estimate the speed of their ships. This technique consisted of putting a weighted log of wood at the end of a rope tied to the back of the boat and placed in the water. In this rope, previously knots had been tied at regular intervals: every 14.5 m. When the boat was stopped, the rope was completely submerged vertically in the water, so no knots were visible. Therefore, the speed was zero knots, but when the ship was at a certain speed knots appeared on the surface. The faster the boat was going, the more horizontal the rope was and therefore the more knots we could see. Today, by convention, a nautical knot or nautical mile (which is 1,000 knots / hour) corresponds to 1,852 km / h. Thus, the unit of measurement for distances at sea is the nautical mile, scientifically defined as the Longitude of the first arc of the meridian at a latitude of 45 ° As we have mentioned, in its corresponding metric measure, its longitude is equal to 1852.3 meters, or 1.852 km / h Let’s see the reason for this equality, referring for simplicity to the equator instead of the meridian. Considering the spherical Earth, the length of all great circles and therefore of the meridians and the equator will be the same. Now, knowing that the equatorial circumference measures 40,000,000 meters and that a circumference contains 21,600 prime numbers (360 ′ x 60 ‘= 21,600), from the relation: 40,000,000 / 21,600: 1,851.85 the correspondence between the first degree, nautical mile and 1,852 meters. The French navy adopts the same measurement of 1,852 meters, while the British and American navies give the mile the value of 1,853 meters, a measure corresponding to the longitude of 1 ′ of meridian arc, at a latitude of 48 °, considering the Earth, elliptical and not spherical. In Anglo-Saxon countries there is also the statute mile, equivalent to 1,609 meters, which is used to measure land, river and lake distances.