iSmart Measure Open converter →

Inch to Millimeter

Convert inch (in) to millimeter (mm) — with the exact factor, a quick-reference table and a free converter that works offline.

1 in = 25.4 mm

Try it

Open the free converter with this conversion pre-loaded — no sign-up, works offline after first load.

Conversion table

Inch (in)Millimeter (mm)
1 in25.4 mm
2 in50.8 mm
5 in127 mm
10 in254 mm
20 in508 mm
50 in1,270 mm
100 in2,540 mm
500 in12,700 mm

How the conversion works

Both units measure length. One inch equals exactly 25.4 mm, so multiply by that factor to convert.

FAQ

How many millimeters in a inch?

1 in = 25.4 mm.

How do I convert inch to millimeter?

Multiply the inch value by 25.4. For example, 10 in × 25.4 = 254 mm.

Where does the factor come from?

The conversion factor is defined in NIST SP 811; both units are length units converted through meter.

Related conversions

Millimeter to Inch Centimeter to Inch Inch to Centimeter Foot to Inch

Conversion factors: NIST SP 811. Computed by the same engine that powers the app.

Powered by iSmart Web