Convert Millimeters ↔ Inches
Type in either box — results update instantly.
Millimeters (mm)
Inches (in)
Formula
in = mm ÷ 25.4 | mm = in × 25.4
Conversion Deck
Convert Millimeters to Inches
This millimeters to inches converter helps you accurately change between small metric and imperial length units. It’s ideal for precision work such as engineering, 3D printing, carpentry, and craft projects where even fractions of a millimeter matter.
The conversion formula is in = mm ÷ 25.4.
For example, 100 mm equals 3.937 inches.
To convert inches to millimeters, use the reverse equation mm = in × 25.4.
This converter updates instantly and accepts decimals for maximum accuracy. You can also use related tools like the centimeters to inches converter or the meters to feet converter for other length conversions.
All conversions are performed locally in your browser for speed and privacy — part of the full suite of free tools at Conversion Deck.