Effortlessly convert between millimeters (mm) and inches (in) with our precision calculator. Get instant, accurate conversions for engineering, construction, and everyday use. One millimeter is equal to 1/25.4 of an inch (in). Inch (in or ″) is a unit of length. One inch is equal to 1/12 of a foot (ft). One inch is equal to 1/36 of a yard (yd). One inch is equal to 25.4 millimeters (mm). 1 millimeter is equal to 0.03937007874 inches: Convert millimeters to inches (mm to in) with the length conversion calculator, and learn the millimeter to inch formula. To make the conversion easier, you can use the millimeters to inches conversion calculator provided on this page. This tool will calculatate the value for you and also give the result in fractional form if required.