The common metric units of length are millimeter, centimeter, meter and kilometer. When making a measurement, you will need to choose which unit to use.
Length - according to the geometric definition, length is a quantity that describes the longest dimension of an object. In Euclidean space, it’s how far 2 specific points are from each other. The standard SI unit of length is the meter.
All Length Converters
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. A meter has been officially defined to be the distance traveled by light in a vacuum in 1/299,792,458 second. All other length and distance measurements in the metric system derive from the meter (eg. km= 1000m, 1m= 1000mm).