Inches to MM Converter
Useful for matching imperial fasteners, drill bits and pipe fittings to metric parts.
1 in = 25.4 mm
millimeters
1 in = 25.4 mm
How to convert inches to millimeters
Multiply the number of inches by 25.4.
Formula
mm = in × 25.4
Examples
- 0.25 in × 25.4 = 6.35 mm
- 0.75 in × 25.4 = 19.05 mm
- 2 in × 25.4 = 50.8 mm
Inches to millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.0625 | 1.5875 |
| 0.125 | 3.175 |
| 0.1875 | 4.7625 |
| 0.25 | 6.35 |
| 0.3125 | 7.9375 |
| 0.375 | 9.525 |
| 0.5 | 12.7 |
| 0.625 | 15.875 |
| 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 |
Values rounded to 4 decimal places or 4 significant digits.
About inches
The inch has been defined as exactly 2.54 centimeters since the 1959 international yard and pound agreement. It is used worldwide for screen sizes and wheel diameters, and in the US for most short measurements.
About millimeters
The millimeter is one thousandth of a meter. It is the standard unit on engineering and architectural drawings, and it is used for small, precise dimensions such as screw diameters, rainfall totals and the thickness of a phone.
Frequently asked questions
How many millimeters are in one inch?
One inch equals 25.4 millimeters.
How do I convert inches to millimeters?
Multiply the number of inches by 25.4. For example: 0.75 in × 25.4 = 19.05 mm.
How many inches are in one millimeter?
One millimeter equals 0.03937 inches.
Is the in to mm conversion exact?
Yes. The factor follows directly from the official definitions of both units, so the only rounding is in how many decimals are displayed.