Inches to Millimetres Converter
Convert inches (in) to millimetres (mm) instantly. Length conversions come up when reading overseas furniture specs, cycling the Round Island Route in kilometres while a foreign app shows miles, or checking marine distances in the Singapore Strait in nautical miles.
Result
- Millimetres
- 25.4 mm
How to use the inches to millimetres converter
- Enter the inches (in).
- The results update as you type, or press Calculate.
- Read the millimetres first, then the supporting figures below it.
Formula
Millimetres = inches × 25.4
Worked example
For example, with these inputs:
- Inches (in): 1
the calculator returns:
- Millimetres: 25.4 mm
Inches to Millimetres table
| Inches | Millimetres |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 100 in | 2,540 mm |
| 250 in | 6,350 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
About this conversion
Length conversions come up when reading overseas furniture specs, cycling the Round Island Route in kilometres while a foreign app shows miles, or checking marine distances in the Singapore Strait in nautical miles.
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
Frequently asked questions
How many millimetres are in one inche?
1 in = 25.4 mm.
How do I convert in to mm?
Millimetres = inches × 25.4.