Inches to Millimeters Converter

Convert inches to millimeters instantly. Free inches to mm converter with quick reference table, formula, and common conversions for engineering and manufacturing.

25.4
Millimeter (mm)
Input Value
1 in (Inch)
About the thickness of a credit card
1/12 of a foot. Standard in US for small measurements.

How to Convert Inch to Millimeter

Simple formula with a worked example

To convert inch (in) to millimeter (mm), use this formula:

mm = inches × 25.4

Example: Convert 5 in to mm

5 in = 127 mm

To convert back, use: inches = mm ÷ 25.4

Inch to Millimeter Conversion Table

Quick reference for common inch to millimeter conversions

Inch (in)Millimeter (mm)
1 in25.4 mm
2 in50.8 mm
5 in127 mm
10 in254 mm
25 in635 mm
50 in1,270 mm
100 in2,540 mm
250 in6,350 mm
500 in12,700 mm
1,000 in25,400 mm

About Inch and Millimeter

Understanding these length units

Inch (in)

1/12 of a foot. Standard in US for small measurements.

Millimeter (mm)

1/1000 of a meter. Used for precision measurements.

When You Need This Conversion

  • precision engineering
  • 3D printing
  • CNC machining
  • pipe and bolt sizing

Did you know? The exact conversion of 1 inch = 25.4 mm was internationally agreed upon in 1959, finally unifying the slightly different inch definitions used by the US and UK.

Frequently Asked Questions

Common questions about converting inch to millimeter

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Last updated Mar 21, 2026