Inches to Kilometers Converter

An inch is exactly 2.54 centimeters, or 25.4 millimeters. Twelve inches make one foot and thirty-six make a yard, so the inch sits inside two larger imperial units.

Screen and tyre sizes are given in inches, as are pipe and hose diameters, wrench openings and the diagonal of a television. Rainfall is still recorded in inches in some countries.

Because the inch has an exact metric value, converting to millimeters or centimeters introduces no error beyond display rounding. This site shows at most six decimal places, so very small fractions may appear shortened.

A frequent mistake is reading a pipe size as an exact outside diameter when trade sizes are nominal. Another is converting inches to centimeters and then labelling the answer millimeters.

People confuse inches with centimeters most often of all, then with feet. Screen and pipe sizes are inches, while fabric and body measurements may be either, and a twelvefold confusion between inches and feet is the usual consequence of misreading a unit label in practice.

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.