There are 1000000 (one million) millimeters in a kilometer (1000000 mm in 1 km). To convert from kilometers to millimeters, multiply the kilometer value by 1000000 and to convert from millimeters to kilometers, multiply the millimeter value by 0.000001 (or divide by 1000000).
1 Kilometer = 1 000 000 Millimeters
Kilometer is a metric length unit and equals to 1000 meters. The abbreviation is "km".
Millimeter is a metric length unit and equal to one thousandth of a meter. The abbreviation is "mm".