Aviation Terminology - Nautical Miles (NM)

When flying, we often hear the term "Nautical Mile (NM)". In fact, it is originated from sea navigation. It is a unit of distance measurement.


1 nautical mile is approximately equal to the distance of one minute of arc measured along any Great Circle. 

The whole great circle is 360 degrees. It takes 60 mins to travel 1 degree along any great circle. For each arc minute, the distance of travel is 1/60 of 1 degree, i.e. 1 nm which is also equal to 1852 meters (or 1.852 km). 

To convert it into statute miles, it is approximately 1.15 miles. 
To convert it into feet, it is approximately 6074 ft (1 m = 3.28 feet).

Therefore, by simple calculation, we know how long it takes to travel along a great circle:

360 degrees x 60 mins = 21600 mins

Since 1 minute of arc equals to 1  nm, the total distance traveled is 21600 nm i.e. 40003 km (1 nm = 1.852 km) or 24840 miles (1 nm = 1.15 miles).