Twenty millimeters is the equivalent of 25/32 of an inch or approximately 0.79 inches. One millimeter is about 3/64 of an inch or about 0.039 inches. Twenty millimeters also equals 2 centimeters.
The millimeter and the centimeter are units of length in the metric system, a system of measurement based on units of 10. Other units in this system are the meter, which is equal to 1,000 millimeters, and the decimeter, which is equal to 100 millimeters.
The inch is a U.S. customary unit of length based on the imperial system of measurement, a system used primarily in the United States. Other units in this system are the foot, which equals 12 inches, and the yard, which equals 36 inches.