Kilometers are represented by the letter "km", commonly known as kilometers. In May 1790, a special committee composed of French scientists recommended that one fourth of the total length of the earth's meridian passing through Paris be taken as the length unit - meter. 1km = 1000m = 10000 decimeters = 100000 cm.
Length unit refers to the basic unit for measuring spatial distance. It is the basic unit formulated by human beings to regulate length. The international unit is "meter" (symbol "m"), and the common units are nanometer (nm) and micron（ μ m) , mm, cm, DM, m, km, etc. Length units play an important role in various fields.
The traditional Chinese units of length are: Li, Zhang, Chi, inch, Xun, Ren, Fu, close, small, step, Chang, arrow, banquet, few, track, pheasant, milli, centi, minute, etc.
1 foot = 10 feet; 1 foot = 10 inches; 1 inch = 10 minutes; 1 minute = 10 centigrade.
1 Zhang ≈ 3.33 m; 1 foot ≈ 3.33 decimeter; 1 inch ≈ 3.33 cm.
1km (km) = 1000m; 1m (m) = 100 cm; 1 cm (CM) = 10 mm.
1 Li = 150 Zhang = 500 m; 2 li = 1 km (1000 m).