Miles to Nautical miles Converter

Miles (mi). A mile is exactly 1,609.344 meters, or about 1.609 kilometers. It is the standard road-distance unit in the United States and the United Kingdom.

Nautical miles (nmi). A nautical mile is exactly 1,852 meters — one minute of latitude. It is the standard unit for maritime and air navigation, which is why ship and aircraft speeds are given in knots per hour.

Metric-to-metric conversions are exact. Imperial figures are exact by definition but are rounded for display, so a value converted back and forth can differ in the final digit.

Inside the metric units every length conversion is a shift of the decimal point, so millimeters to centimeters, meters to kilometers and the rest can be done by moving it. Which way, and how far, follows from the prefix alone.

Converting between metric and imperial is not a shift but a single exact multiplication, and the factor is the same one for that pair however large or small the value. The trap is mixing the two systems halfway, as when a distance is stated in meters and inches in the same sentence.

To check a length conversion, run it backwards, or convert through a familiar middle value such as a meter or a foot. The one thing to keep straight is pairs that differ by a thousand rather than by ten, since those are where a misplaced decimal point survives unnoticed.