1 inch to millimeters

1 inch = 25.4 millimeters

Rounded to a practical precision: 25.4 mm.

inches

millimeters

How the calculation works

One inch is 25.4 millimeters, so:

1 in × 25.4 = 25.4 mm

Reversing it, 25.4 millimeters ÷ 25.4 returns 1 inches.

Nearby values

Inches	Millimeters
0.5 in	12.7 mm
1 in	25.4 mm
1.5 in	38.1 mm
2 in	50.8 mm
2.5 in	63.5 mm
3 in	76.2 mm

About these units

Inch (in) — An inch is exactly 25.4 millimetres and is used for screen sizes, pipe diameters and paper dimensions.

Millimeter (mm) — A millimetre is one thousandth of a metre and is the default unit on engineering drawings and rulers.

Frequently asked questions

How many millimeters is 1 inch?

1 inch is 25.4 millimeters.

How do I convert inches to millimeters myself?

Multiply by 25.4. To go back, divide by 25.4 — or multiply by 0.0393701.

Is this figure exact?

The conversion factor between the inch and the millimeter is fixed by definition. The figure above is rounded for readability; the converter carries full precision.

Convert other values

Full inches to millimeters converter · All length converters