How to convert millimeters to inches
To convert a measurement in millimeters to inches, multiply the value by 0.0393700787. The conversion factor comes from the relationship between both units and the meter (the SI base unit of length).
For example, to convert 5 mm to inches: 5 × 0.0393700787 = 0.1968503937 in.
What is a millimeter?
A millimeter is a metric unit of length equal to one thousandth of a meter (0.001 m) or approximately 0.039 inches. Part of the original metric system, the millimeter derives from the Latin 'mille' (thousand). It became essential during the Industrial Revolution for precision engineering.
Common uses of millimeters include: Engineering tolerances and mechanical parts; Rainfall measurement in meteorology; Paper thickness and printing specifications; Dental and medical precision measurements.
What is a inch?
An inch is an imperial unit of length equal to 1/12 of a foot or exactly 25.4 millimeters. Originally defined as the width of a man's thumb, later standardized as three barleycorns laid end to end. Since 1959, defined internationally as exactly 25.4 mm.
Common uses of inches include: Screen and display sizes (TV, phone, monitor diagonals); Screw, bolt, and pipe sizing; Tire rim diameter specifications; Woodworking and carpentry precision.
When you need to convert millimeters to inches
Engineering drawings, 3D printing specifications, and mechanical part catalogs often mix metric and imperial. Machinists and hobbyists convert between millimeters and inches daily.
Millimeters to inches worked examples
Here are some common values converted:
1 mm = 0.0393700787 in 5 mm = 0.1968503937 in 10 mm = 0.3937007874 in 50 mm = 1.968504 in 100 mm = 3.937008 in
Frequently asked questions
How many inches are in one millimeter?
One millimeter (mm) equals 0.0393700787 inches (in). Multiply any value in millimeters by 0.0393700787 to convert to inches.
How do I convert millimeters to inches?
Multiply the value in millimeters by 0.0393700787. For example, 5 mm × 0.0393700787 = 0.1968503937 in.
How do I convert inches to millimeters?
Multiply the value in inches by 25.4, or divide by 0.0393700787. Use the swap button on the converter above to reverse the direction.
Is the millimeter to inch conversion exact?
Yes, the conversion is exact. Since 1959, one inch is defined as exactly 25.4 mm (the international yard and pound agreement), so all metric-imperial length conversions use exact factors.
What is the formula for millimeters to inches?
The formula is: in = mm × 0.0393700787. This is derived from the definition of both units relative to the meter (the SI base unit of length).