19.98 cm. Inch is a traditional unit of length in China and belongs to the municipal unit of measurement. It is a decimal number with "feet" and "feet" and is usually used to measure smaller lengths. Centimeter is a unit of length measurement, which belongs to the metric unit of measurement and is equal to one hundredth of a meter, and is represented by the symbol cm. Its conversion is 1 inch =3.33 cm, and 6 inches =6×3.33= 19.98 cm, so the 6 inches of the morning education machine is 19.98 cm. The conversion between other city systems and metric length is: 1 city ruler = 0.33m; 1 inch =3.33 cm; 1 sheet =3.33 meters.