UnitConInches to Millimeters Converter
Convert inches to millimeters for machining, hardware specs, product design, and technical drawings. This conversion is especially important in manufacturing where imperial drawings must match metric tooling.
Formula
Multiply inches by 25.4 to get millimeters. To reverse, divide millimeters by 25.4 to get inches.
Quick reference
| Inch (in) | Millimeter (mm) |
|---|---|
| 0.25 | 6.35 |
| 0.5 | 12.7 |
| 0.75 | 19.05 |
| 1 | 25.4 |
| 1.5 | 38.1 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 6 | 152.4 |
| 12 | 304.8 |
About these units
Inch
The inch was fixed at exactly 25.4 mm in 1959 under the International Yard and Pound Agreement. Prior to that, the US and UK inch differed slightly, causing confusion in precision manufacturing.
Millimeter
The millimeter (one thousandth of a meter) is the preferred unit for precision engineering in metric countries. Its small size makes it practical for measuring hardware, fasteners, and machined parts without resorting to decimal fractions of a centimeter.
Frequently asked questions
Exactly 25.4 mm, by definition since 1959.
0.25 × 25.4 = 6.35 mm.
12 × 25.4 = 304.8 mm, which is exactly one foot.