Length is the extent of a substance/item measured from end to end. The standard/fundamental/base unit for length is meter; However, there are numerous other units both SI units, Imperial, Customary US units, etc.
Meter is defined as the distance traveled by light in a vacuum within a 1/299,792,458 of a second.
UK imperial units and customary US units are considered less logical progression units, thus not very popular. However, we have developed templates for conversion between SI units, Imperial and Customary units and vice versa.