Kilometers to Miles Converter

The kilometer is exactly 1,000 meters, the unit of length in the International System used for distances between places rather than across a room. It is written km and is the basis of the metric road network.

Road signs, speed limits, odometers and race distances use kilometers in most of the world. Maps quote distances in kilometers, and athletic events such as the marathon are described in kilometers.

One kilometer equals 0.621371 miles, an exact conversion from the definition of the mile as 1,609.344 meters. The displayed figure is rounded, so converting kilometers to miles and back may shift the last digit.

Mixing meters and kilometers is the usual error: a walking route given as 4,000 meters is four kilometers, not forty. A kilometer is also a length unit, so square kilometers measure area.

Kilometers and miles both measure road distance, while meters measure shorter spans inside the same journey. Treating a mile figure as kilometers understates the distance by about a third, and mixing the two within one route confuses every later step.

The international mile is exactly 1,609.344 meters, or 1.609344 kilometers. It descends from the Roman mile of a thousand paces and remains the standard road distance in the United States and the United Kingdom.

Road signs and speed limits, distance markers on highways, running and cycling events and aviation track distances are quoted in miles in those countries. Nautical miles are separate and longer.

Since the mile is defined as 1,609.344 meters exactly, converting to kilometers or feet is exact arithmetic; only the printed result is rounded. A value converted to kilometers and back can return with a changed last digit.

The common error is using a statute mile where a nautical mile is meant, which understates the intended distance by about thirteen percent. Miles also measure length, not area or speed.

Miles measure road distance, kilometers do the same on metric roads, and nautical miles measure sea and air distance. A nautical mile is longer than a statute mile, so a flight quoted in the wrong one is misread by roughly thirteen percent.