Nautical Miles to Kilometers Converter

A nautical mile is exactly 1.852 kilometers:

kilometers = nautical miles × 1.852

Unlike the statute mile, this one was chosen for a reason. A nautical mile is one minute of arc of latitude — one sixtieth of a degree — measured along a meridian. That makes it the only distance unit that maps directly onto a chart: one minute of latitude is one nautical mile, anywhere on Earth.

Because the planet is not a perfect sphere, the real arc-minute varies from about 1,843 m at the equator to 1,862 m at the poles. The 1,852 m figure was fixed by international agreement in 1929 as a round average, so the modern definition is exact and the geometric origin is now an approximation of it.

A nautical mile is about 15% longer than a statute mile: 1 nmi = 1.15078 statute miles.

Where it is still the working unit:

• Aviation. Flight distances, navigation and separation are all in nautical miles. A 3,000 nmi leg is 5,556 km. Speeds are in knots — one knot is one nautical mile per hour.
• Maritime law. Territorial waters extend 12 nmi (22.2 km) from the coast, and an exclusive economic zone reaches 200 nmi (370.4 km). These figures are defined in nautical miles, so their kilometre equivalents are always the converted number.
• Charts. Distance is read off the latitude scale at the side of the chart, never the longitude scale at the top — longitude minutes shrink toward the poles.

For a rough conversion, add 85% to the nautical miles.