Instant, two-way conversion across common engineering units.
1 in = 25.4 mm(Inch → Millimetre)
To convert inches to millimeters, multiply the value by 25.4. Length values feed directly into setting out, spans and drawing dimensions, so the converter keeps full decimal precision in both directions.
The inch (in) is the base small unit of the imperial and US customary length system.
The millimeter (mm) is one thousandth of a meter and the working unit of technical drawing in most of the world.
1 in equals 25.4 mm.
Multiply the value by 25.4. For example, 10 in equals 254 mm.
1 mm equals 0.039370079 in. The converter above works in both directions, so you can type into either field.
Most architectural and structural drawings outside the US are dimensioned in millimeters to avoid decimal points, while site levels, grids and areas are stated in meters.
Yes. The inch has been defined as exactly 25.4 mm since 1959, so foot, yard and mile conversions are exact rather than rounded.
Yes. Every unit conversion runs in your browser, needs no account and is free for professional use.