Formula
Convert inches to millimeters with:
mm = in * 25.4
Example
1 in = 25.4 mm
inches to millimeters table
Questions
How many millimeters are in a inche?
One inche is 25.4 millimeters. Enter any value above to convert instantly.
What is the formula to convert inches to millimeters?
Use mm = in * 25.4. The calculator applies this for every value you type.
Is this conversion exact?
Yes — it uses the standard conversion factor (mm = in * 25.4), rounded to 6 significant digits for display.