Length Converter

Convert length units with the factor behind each answer. The inch, foot and yard are defined exactly in metres, so the factors are exact.

Value

From

Result3.937007874 in

1 mm = 0.03937007874 in

Common conversions

Since 1959 the inch has been exactly 25.4 mm, the foot exactly 0.3048 m and the yard exactly 0.9144 m. The statute mile is exactly 1,609.344 m.

Conductor diameters are in mm in IEC practice and in mil or AWG in US practice. For a wire gauge to mm² conversion, use the wire gauge calculator.

Every unit in terms of the base unit shown. To convert, multiply by the factor of the unit you have and divide by the factor of the unit you want.

Unit	Equals	What it is
mm	0.001 m	Millimetre. Cable sizes, conductor diameters and drawings.
cm	0.01 m	Centimetre, a hundredth of a metre.
m	1 m	Metre, the SI unit of length.
km	1,000 m	Kilometre. Cable routes and line lengths.
in	0.0254 m	Inch, exactly 25.4 mm by definition.
ft	0.3048 m	International foot, exactly 0.3048 m.
yd	0.9144 m	Yard, exactly 0.9144 m.
nm	1 × 10⁻⁹ m	Nanometre, a billionth of a metre. Wavelengths of light.
µm	1 × 10⁻⁶ m	Micrometre (micron), a millionth of a metre. Coating and film thickness.
mil	2.54 × 10⁻⁵ m	Thousandth of an inch (0.001 in). Wire diameters and insulation thickness in US practice.
mi	1,609.344 m	Statute mile, exactly 1,609.344 m.
nmi	1,852 m	Nautical mile, exactly 1,852 m. Marine and aviation distances.

in = mm × 0.03937007874. For example, 100 mm is 3.937007874 in.

mm = in × 25.4. The Swap button above reverses the direction for any pair of units.