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Millimeter to Inch

mm
Inch (in)
in

in = mm × 0.0393701

Quick Reference: Millimeter to Inch

mmin
100.3937
250.9843
501.9685
1003.937
2509.8425
50019.685

How to Convert Millimeter to Inch

Formula:

in = mm × 0.0393701

Example:

25 mm = 0.9843 in

  1. Enter the value in Millimeter you want to convert
  2. The result is calculated automatically
  3. Copy your result in Inch or continue converting

About Millimeter and Inch

Millimeters provide high-precision metric measurements, while inches are the standard in imperial systems. One inch equals exactly 25.4 millimeters. This conversion is critical in precision engineering, manufacturing, and detailed technical work where accuracy matters.

Common Uses for This Conversion

Engineers, machinists, and craftspeople use this conversion daily for specifications, tolerances, and detailed measurements. It's common in jewelry making, 3D printing settings, bolt and screw sizing, and electronic component dimensions.

💡Did You Know?

The millimeter became internationally standardized in 1960 as part of the International System of Units (SI). Many technical fields use millimeters because they avoid decimal points for measurements under a centimeter.

Frequently Asked Questions

1 mm = 0.0394 inches (1 ÷ 25.4 = 0.03937). This is less than 1/16 of an inch (0.0625 in). A standard credit card is about 0.76 mm thick. Engineers working with precision parts — bolts, drill bits, 3D-print settings — commonly work in tenths of millimeters, so 1 mm is a significant tolerance step.
5 mm = 0.197 inches — close to 3/16 in (0.1875 in). The 3.5 mm headphone jack (standard audio connector) equals 0.138 in; a 5 mm Allen key (hex key) is one of the most common sizes for flat-pack furniture assembly and bicycle components.
10 mm = 0.394 inches, approximately 25/64 in and close to 3/8 in (0.375 in). A 10 mm socket wrench is one of the most widely used sizes in automotive and appliance repair worldwide. In jewelry, a 10 mm round gemstone or pearl is a popular pendant and earring size.
25.4 mm = exactly 1 inch. This is the precise international definition established in 1959: 1 international inch = 25.4 mm. To convert any millimeter value to inches, divide by 25.4 (or multiply by 0.03937).

Related Conversions

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