Inches to Millimeters converter
Convert inches (in) to millimeters (mm) — results update instantly as you type.
Inches to Millimeters
1 in = 25.4 mm
How to convert Inches to Millimeters
Length is the most everyday measurement there is — yet the world still splits between the metric system (millimeters, centimeters, meters, kilometers) and the imperial system (inches, feet, yards, miles). This converter bridges both, plus nautical miles used in aviation and shipping.
Every length unit is defined as an exact multiple of the meter, the SI base unit. An inch is exactly 0.0254 meters and a mile is exactly 1609.344 meters, so converting between any two units is a single multiplication — no approximations involved.
Formula
in × 25.4 = mm
Multiply your inches value by 25.4 to get millimeters. For the reverse, divide by the same factor.
Inches to Millimeters conversion table
| Inches | Millimeters |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 25 in | 635 mm |
| 100 in | 2,540 mm |
Common use cases
- Converting body height between centimeters and feet/inches
- Road trip distances between kilometers and miles
- Screen sizes, fabric, and DIY measurements in inches vs centimeters
- Marine and aviation distances in nautical miles
Frequently asked questions
Exactly 2.54 centimeters. The inch has been defined as precisely 25.4 millimeters since the international yard and pound agreement of 1959.