Nautical Mile Converter

A nautical mile is exactly 1,852 meters, while a statute mile is exactly 1,609.344 meters. A nautical mile is approximately one minute of latitude along a meridian, which makes it useful for navigation. Do not substitute statute miles on a nautical chart.

The international nautical mile is defined as exactly 1,852 meters. National and international bodies adopted that standard to make navigation calculations consistent. Older national definitions differed, so historical records can use another value.

A knot is one nautical mile per hour, so 1 knot equals 1.852 km/h exactly and about 1.15077945 mph. The name comes from chip-log methods that used a knotted line and timed glass to estimate a ship's speed. The exact line spacing and timing varied by period and practice.

Knots are commonly used for aircraft and vessel speeds and for marine weather reports. One knot is one nautical mile per hour, so the unit aligns speed with nautical-chart distances.

For mph, multiply knots by 1.15 (or add about 15 percent), so 20 knots is roughly 23 mph. For km/h, multiply knots by 1.85 (or roughly double and subtract a bit), so 20 knots is roughly 37 km/h. The exact factor is 1.852, so doubling is accurate to within 8 percent, which is close enough for back-of-the-envelope weather and travel math.