An inch is also a unit of length in US customary systems of measurement. An inch is equivalent to 25.4 millimeters.
One mm is equal to 0.03937007874 inches. We can also define it as I mm is equal to 1/25.4 inches.
Therefore, inch and millimeter both are units to measure length.
If you want to convert the millimeter into inches, we can multiply the millimeter value by 0.03937007874.
We can understand with an example if you want to convert 100 millimeters into inches.
Inches = mm X 0.0393701
100 X 0.0393701 = 3.93701 inches
We can also convert millimeters to inches with the following simple formula:
Millimeter = inches/25.4
100 inch/25.4 = 3.93701 inches