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 decimeter?
A decimeter (dm) is one tenth of a meter, or 10 centimeters. The 'deci' is the SI prefix for 10^-1.
The decimeter is rarely used by itself, since people go from centimeters straight to meters. You mostly meet it as the cubic decimeter, which is exactly one liter.
A decimeter is about 3.937 inches, so just under four. Divide inches by 3.937 – or multiply by 0.254 – to go the other way.