To convert 1 inch to millimeter, multiply the inch value by the conversion factor of 25.400000. For 1 inch, the calculation is 1 × 25.400000 = 25.4000 millimeter.

1 inch equals exactly 25.400000 millimeter. For practical purposes and common applications, this is often rounded to 25.4000 millimeter.

Objects measuring approximately 1 inch include a US Quarter coin (0.955 inch), a CR2032 Lithium Coin Cell Battery (0.787 inch), and a standard soda bottle cap (1.06 inch).

Converting inch to millimeter is useful for international collaboration, precision engineering, manufacturing compatibility, and adhering to global scientific and technical standards. It ensures accuracy in fields like aerospace, medical device production, and automotive design.

The easiest way to remember is to associate 1 inch with 25.4 millimeters. A simple mental trick is to think 'two and a half centimeters plus a little bit.' Visualizing a US Quarter coin (0.955 inch) as roughly 24mm or a standard soda bottle cap (1.06 inch) as about 27mm can also serve as quick references.