Aviation distance conversions
Aviation navigation normally uses nautical miles, but performance charts, airport dimensions, terrain data and general maps may use feet, meters, statute miles or kilometers. The safest approach is to convert everything into one consistent unit before doing the next calculation.
Nautical mile
One nautical mile is exactly 1,852 meters. It is about 1.1508 statute miles and about 6,076 feet. Because one knot is one nautical mile per hour, nautical miles fit naturally with aviation speed and time calculations.
Statute miles
Statute miles are the miles used on U.S. roads. To convert NM to statute miles, multiply by about 1.1508. A 100 NM route is therefore about 115 statute miles.
Kilometers
Multiply nautical miles by 1.852 to get kilometers. A 50 NM leg is 92.6 km. To return to nautical miles, divide kilometers by 1.852.
Feet and meters
Runway lengths and obstacle dimensions can appear in feet or meters. One foot is exactly 0.3048 meter. One meter is about 3.281 feet. Do not use a nautical-mile conversion when the source is giving a vertical or runway dimension in feet.
Distance on a chart versus altitude
Horizontal distance and vertical height may use different units in the same problem. A climb-gradient problem, for example, may combine feet of climb with nautical miles traveled. Keep each unit labeled until the formula is complete.
Reasonableness checks
A nautical-mile value should be smaller than the equivalent statute-mile value and smaller than the equivalent kilometer value. If the number moved in the opposite direction, check the conversion.
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