1 cm = 1 cm. China's ancient weights and measures are now called the market system. When western weights and measures were introduced, China's Chinese characters were added according to China's custom. Such as meter, centimeters and millimeter. These old names were later changed to international units: meters, centimeters and millimeters.

The unit of length refers to the basic unit for measuring spatial distance, which is formulated by human beings to standardize the length. Its international unit is "meter" (symbol "m"), and commonly used units are millimeter (mm), centimeter (cm), decimeter (dm), kilometer (km), meter (m), micron (micron) and nanometer (nm).