Convert inches to millimeters instantly. Enter a measurement in inches (decimals work for fractions) to get the exact value in millimeters.
How to convert inches to mm
One inch is exactly 25.4 millimeters, so to convert inches to millimeters you multiply by 25.4.
Formula: millimeters = inches × 25.4
Example: A ¼-inch bolt is 0.25 × 25.4 = 6.35 mm. A ⅜-inch drill bit is 0.375 × 25.4 = 9.525 mm.
Tip: To convert a fraction, divide the top number by the bottom first: ⅝ inch = 5 ÷ 8 = 0.625 in, and 0.625 × 25.4 = 15.875 mm.
| Inch | Millimeter |
|---|---|
| 0.125 | 3.175 |
| 0.25 | 6.35 |
| 0.375 | 9.525 |
| 0.5 | 12.7 |
| 0.75 | 19.05 |
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127 |
| 6 | 152.4 |
| 12 | 304.8 |
Need a different unit? The Length Converter handles every common length unit.