Inch (in):
The inch (in) is a unit in the imperial and U.S. customary systems—one inch is exactly 2.54 centimeters. It’s the standard for describing screen sizes, hardware, clothing measurements in some contexts, and many common household dimensions. Twelve inches make a foot, which is heavily used in construction and daily life in the U.S.
Millimeter (mm):
The millimeter (mm) is one of the smallest commonly used metric units. It’s frequently used in engineering, machining, and manufacturing where fine tolerances matter. Architects, engineers, and product designers rely on millimeters for accuracy in drawings and specifications.
How to convert inches to millimeters
Option 1: The fastest way – Use our converter
For instant results, just type your measurement into the in to mm converter at the top of this page. It's quick, accurate, and hassle-free.
Option 2: The diy way – Use the formula
If you prefer to calculate it yourself, it's straightforward. You only need to remember one number: 25.4. This is because one inch is internationally defined as exactly 25.4 millimeter.
The formula is simple:Millimeters = Inches × 25.4
Here's how to do it:
Take your measurement in inches.
Multiply that number by 25.4.
The answer is the measurement in millimeters.
Example: Let's convert 10 in to mm.
Calculate: 10 × 25.4 = 254
Result: equals 254 mm
It's really that easy.