Inch (in) to Millimetre (mm) Converter
1 in = 25.4 mm
To convert Inch (in) to Millimetre (mm), multiply the value by 25.4 — one in is exactly 25.4 mm. Both are units of Length. The table below lists the most-searched conversions, and the converter handles any value.
Formula
mm = in × 25.4in to mm conversion table
Frequently asked questions
How many mm are in 1 in?+
1 Inch equals 25.4 Millimetre, so 1 in = 25.4 mm.
What is the formula to convert in to mm?+
Multiply the number of Inch by 25.4. In other words: mm = in × 25.4.
How much is 1 in in mm?+
1 Inch = 25.4 Millimetre (1 in = 25.4 mm).
Is this conversion exact?+
Yes. The factor used is the unit’s official definition; results are rounded to 10 significant digits for readability.