Convert millimeters to inches instantly. Enter a measurement in millimeters to get the exact value in inches — useful for tools, bolts, drill bits, jewellery and rainfall.
How to convert mm to inches
One inch is exactly 25.4 millimeters, so to convert millimeters to inches you divide by 25.4.
Formula: inches = millimeters ÷ 25.4
Example: 10 mm ÷ 25.4 = 0.394 inches. A 13 mm spanner is 0.512 inches — very close to a ½-inch (12.7 mm) spanner, which is why the two are often confused.
Tip: Imperial tools are usually sized in fractions of an inch. 6.35 mm is ¼ in, 9.525 mm is ⅜ in and 12.7 mm is ½ in.
| Millimeter | Inch |
|---|---|
| 1 | 0.03937007874 |
| 2 | 0.07874015748 |
| 3 | 0.1181102362 |
| 5 | 0.1968503937 |
| 6 | 0.2362204724 |
| 8 | 0.3149606299 |
| 10 | 0.3937007874 |
| 12 | 0.4724409449 |
| 15 | 0.5905511811 |
| 20 | 0.7874015748 |
| 25 | 0.9842519685 |
| 50 | 1.968503937 |
| 100 | 3.937007874 |
Need a different unit? The Length Converter handles every common length unit.