Knots are a speed measurement that is nautical miles per hour. This unit is typically used in maritime and aviation. There have historically been different nautical miles used and, thus, different variations of knots. However, we have based our knots calculator on the international nautical mile which is commonly used thoughout the world today.
This is a measurement of speed typically used in non-metric countries for transport such as the USA. The United Kingdom also uses this on the roads although officially the metric system has been adopted. Road speed limits are given in miles per hour which is abbreviated as mph or mi/h.