Convert Inch to Millimeter
Use this free converter to change inches (in) into millimeters (mm). Inch and millimeter both measure length. As a quick reference, 1 in equals 25.4 mm, and 1 mm equals 0.039370079 in.
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Millimeter (mm)
25.4
1 in = 25.4 mm
Length conversion table
| Inch | Millimeter |
|---|---|
| 0.01 | 0.254 |
| 0.1 | 2.54 |
| 0.5 | 12.7 |
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 5 | 127 |
| 10 | 254 |
| 20 | 508 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
| 1,000 | 25400 |
How to convert Inch to Millimeter
Multiply the inch value by 25.4 to get millimeters.
- Enter the number of inches you want to convert.
- The converter instantly shows the equivalent value in millimeters.
- Worked example: 15 in × 25.4 = 381 mm.
- Use the swap button to reverse the conversion (millimeter to inch).
About these units
Inch (in)
- Definition
- An inch (in) is an imperial unit of length equal to exactly 2.54 centimeters, with twelve inches making a foot.
- History
- Originally the width of a thumb, the inch was standardised to 25.4 mm internationally in 1959.
- Current use
- Inches measure screen sizes, tyre and pipe dimensions, and everyday lengths in the US and UK.
Millimeter (mm)
- Definition
- A millimeter (mm) is one thousandth of a meter, used where small, precise measurements are needed.
- History
- Like other metric subdivisions it was defined in the 1790s using the prefix "milli-" (one thousandth).
- Current use
- Engineers, machinists, and manufacturers specify tolerances in millimeters, and rainfall is commonly reported in mm.
Frequently asked questions
How many millimeters are in a inch?
There are 25.4 mm in 1 in. To convert, multiply the number of inches by 25.4.
How do I convert inches to millimeters?
Multiply the inch value by 25.4 to get millimeters. For example, 10 in = 254 mm.
Is this inch-to-millimeter converter free?
Yes. This converter is completely free, runs entirely in your browser, and requires no sign-up. Your inputs never leave your device.
Convert Inch to other length units
| Unit | 1 Inch equals |
|---|---|
| Meter (m) | 0.0254 m |
| Kilometer (km) | 0.0000254 km |
| Centimeter (cm) | 2.54 cm |
| Millimeter (mm) | 25.4 mm |
| Micrometer (µm) | 25400 µm |
| Nanometer (nm) | 25400000 nm |
| Mile (mi) | 0.000015782828 mi |
| Yard (yd) | 0.027777778 yd |
| Foot (ft) | 0.083333333 ft |
| Nautical Mile (nmi) | 0.000013714903 nmi |
| Light Year (ly) | 2.6848e-18 ly |