There is more than one type of Nautical Mile
There are a few different types of Nautical Mile. On this site we have conversions for US Nautical miles, UK Nautical miles and International Nautical miles. Please either select the appropriate unit on the selection above of click the required unit in the links below:
What is a nautical mile?
A nautical mile is the unit of distance at sea and in the air, and is exactly 1,852 meters. It began as one minute of latitude along any meridian, which varies slightly because the Earth is not a perfect sphere, so a fixed length was agreed internationally.
Latitude is the reason for the length: a degree has 60 minutes, so a nautical mile is a sixtieth of a degree and 21,600 of them go round the Earth. That makes the latitude scale on a chart a distance scale too. Territorial waters extend up to 12 nautical miles from a coast.
What is a UK Nautical Mile?
The UK nautical mile was based on one minute of latitude, ie 1/60th of a degree. The Earth is not a perfect sphere, so a minute of latitude varies slightly with latitude, which is why a fixed length had to be chosen.
The UK nautical mile, also called the Admiralty mile, was fixed at 6,080 feet, which is 1,853.184 meters. That is 1.184 meters longer than the international nautical mile of 1,852 meters (6,076.11549 feet), which the UK adopted in 1970.