The unit of length meter originated from 1688, and the British philosopher and priest John Wilkins put forward the necessity of decimal standard length unit system.

1675, the Italian scientist Ti Tuo livio Bratini first used the word metro cattolico in his paper, which originated from the Greek μ? τρον καθολικ? Derived from ν, it means "universal unit of measurement".

Length unit conversion:

1 ft = 10 ft; 1 ft = 10 inch; 1 inch = 10 points; 1 = 10%.

1 sheet ≈ 3.33m; 1 ft ≈3.33 decimeter; 1 inch ≈3.33 cm.

1k m = 1000m； 1m = 100cm； 1 cm = 10/0mm.

1 Li = 150 sheets = 500m; 2 Li = 1 km.

Commonly used units are millimeter (mm), centimeter (cm), decimeter (dm), kilometer (km), meter (m), micron (micron), nanometer (nm) and so on.