Convert Inches to Millimeters
in to mm · length conversion
What are inches and millimeters?
An inch is an imperial unit equal to exactly 2.54 cm, widely used in the US and UK. A millimeter is one-thousandth of a meter, about the thickness of a credit card. For scale: a doorway is about 2 m (6.6 ft) tall, and a marathon is 42.2 km (26.2 mi).
How to convert inches to millimeters
1 in = 25.4 mm. To convert, multiply the number of inches by 25.4. For example, 5 in = 127 mm, and 20 in = 508 mm. To go the other way, multiply millimeters by 0.0393701 (since 1 mm = 0.0393701 in).
Inches to Millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 5 | 127 |
| 10 | 254 |
| 20 | 508 |
| 50 | 1,270 |
| 100 | 2,540 |
FAQ
What is 1 in in mm?
1 in = 25.4 mm. To convert any amount, multiply the number of inches by 25.4.
How do I convert millimeters back to inches?
Go the other way: 1 mm = 0.0393701 in, so multiply millimeters by 0.0393701 to get inches.
Is a inche bigger than a millimeter?
Yes — 1 in is the larger unit, equal to 25.4 mm.
Are these length conversions exact?
They use the standard internationally-defined conversion factors. Results are rounded to six significant figures for readability, which is accurate enough for everyday and most technical use.