Volt is an ancient unit of measurement. In ancient times, the symbol 1 was equal to 4 inches, which was about the width of 4 fingers. The inch is the traditional unit of length in China. In terms of conversion unit, 1 inch is equal to 3.33333 cm, and 1 supports about 4 inches. Then it can be calculated that 4 inches is 13.33332 cm, and then 1 support is about 13 cm. Commonly used units of length measurement: kilometers, meters, decimeters, centimeters and millimeters; 2. Common weight units: mg, g, kg, ton, domestic common: 2 kg, kg, 3. Common volume units: cubic centimeter, cubic decimeter, cubic meter, 4. Common area units: square meter, square centimeter, square decimeter, square millimeter, 5. Common volume units: liter, milliliter.