About this converter

MM ↔ Inches is a free, browser-based length conversion tool built for engineers, machinists, woodworkers, 3D-printing hobbyists, and everyday DIY users who need dependable conversions between millimeters and inches.

How our conversions are calculated

All conversions on this site are based on the international inch, which has been defined since 1959 as exactly 25.4 millimeters. To convert millimeters to inches we divide by 25.4; to convert inches to millimeters we multiply by 25.4. Values are displayed to up to six decimal places, and where useful we also render the nearest standard fraction (1/16, 1/32, or 1/64 of an inch).

Who runs this site

This site is an independent project maintained by a small team of developers. We do not sell products, we do not collect personal information beyond basic anonymous analytics, and the tool is free to use. If you have feedback, corrections, or feature requests, please visit our contact page.

Editorial standards

Every conversion, chart, and preset page on this site is programmatically generated from the exact 25.4 mm/inch definition. We do not use approximations, and rounding is applied only for display. When a page states a fractional equivalent (e.g. "10 mm ≈ 25/64″"), the fraction is the closest match to the specified denominator, not the exact value.