A conversion factor used to convert units of length expressed in the metric system (i.e., centimeters) to an English measurement (i.e., inches), as 1 centimeter equals 0.394 inch. Thus, to convert to inches, the number of centimeters is multiplied by 0.394 (i.e., a length that is 12.7 centimeters long would be converted as 12.7 x 0.394 = 5 inches). To convert to millimeters, the number of inches is multiplied by 0.0394 (as there are 10 millimeters in a centimeter, and 0.0394 inch in a millimeter). Thus, a 127-millimeter length would be converted as 127 x 0.0394 = 5 inches.

To convert from inches to metric, the number of centimeters in one inch can be used. (See Inches-to-Metric Conversion.)