4 km to miles Unit Conversion Calculator km to miles Kilometer Mile Meter Centimeter Millimeter Angstrom Fathom Yard Foot Inch Hand Finger Bamboo Barleycorn Mile Kilometer Meter Centimeter Millimeter Angstrom Fathom Yard Foot Inch Hand Finger Bamboo Barleycorn Kilometer, often abbreviated as 'km', is a unit of length in the metric system, primarily used to measure longer distances.