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Length
Millimeters to Inches
Convert millimeters (mm) to inches (in). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 mm = 0.03937 in
Millimeters to Inches Conversion Table
Common values, ready to copy:
| millimeters | inches |
|---|---|
| 1 mm | 0.03937 in |
| 2 mm | 0.07874 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.393701 in |
| 25 mm | 0.984252 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.937 in |
| 1,000 mm | 39.3701 in |
Formula
inches = millimeters × 3.93700787e-2
Length conversions use the SI definition: 1 inch is exactly 0.0254 meters and 1 mile is exactly 1,609.344 meters. The factor above is the exact ratio between millimeter and inch.
About Millimeters and Inches
Millimeters (mm): One thousandth of a meter, where the meter was originally defined in 1799 as one ten-millionth of the equator-to-pole distance, and is now defined by the speed of light. Common uses: The default precision unit in engineering drawings, machining tolerances, manufacturing specifications, and most metric-country construction blueprints.
Inches (in): From the Latin uncia meaning one-twelfth; originally a thumb-width unit, defined as exactly 2.54 centimeters since the 1959 International Yard and Pound Agreement. Common uses: US construction, screens and devices, clothing sizes (waist, chest), paper sizes, and a near-universal global unit for TV and monitor diagonals.
How the conversion works
Length conversions use the SI definition: 1 inch is exactly 0.0254 meters and 1 mile is exactly 1,609.344 meters. The factor above is the exact ratio between millimeter and inch.
The exact relationship is inches = millimeters × 3.93700787e-2, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between millimeters and inches comes up wherever length measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.