Inches to mm converter

Author: Henrick Yau

- 5 August 2026

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Convert between inches and millimetres easily with this calculator. Useful for engineering, construction, manufacturing, and international measurement standards.

Length Conversion

From:

To:

Value:

Display Options

Decimal Places:

Show conversion formula

Conversion Result

Result

0.00

millimetres (mm)

Conversion Formula

Common Values

Inches	Millimetres	Common Usage
1/8"	3.175 mm	Thin materials, small electronic components
1/4"	6.35 mm	Standard plywood thickness, hex wrenches
1/2"	12.7 mm	Common pipe diameter, tool sizes
1"	25.4 mm	Lumber dimensions, standard measurements
3"	76.2 mm	Camera lenses, small packaged goods
12"	304.8 mm	Rulers, tile dimensions (1 foot)

About Length Measurements

Measurement systems vary around the world. The United States primarily uses imperial units like inches, while most other countries use the metric system with millimetres.

Conversion Facts

1 inch = 25.4 millimetres (exact conversion)
1 millimetre = 0.03937 inches
1 foot = 304.8 millimetres (12 inches)
1 yard = 914.4 millimetres (36 inches)
1 metre = 39.37 inches (1000 millimetres)

Common Applications

Engineering: Technical drawings, precision machinery, tolerances
Manufacturing: Component dimensions, material thickness
Construction: Building materials, architectural plans
Woodworking: Lumber dimensions, furniture making
Electronics: Circuit board dimensions, component sizing

Fraction to Decimal Conversion

Fraction (inch)	Decimal (inch)	Millimetres
1/16"	0.0625"	1.5875 mm
1/8"	0.125"	3.175 mm
1/4"	0.25"	6.35 mm
3/8"	0.375"	9.525 mm
1/2"	0.5"	12.7 mm
5/8"	0.625"	15.875 mm
3/4"	0.75"	19.05 mm
7/8"	0.875"	22.225 mm
1"	1.0"	25.4 mm

Why convert inches to millimetres?

Converting inches to millimetres is often necessary for various tasks. This converter simplifies that process. It’s particularly handy for engineers, builders, and designers who work with different measurement systems. By using this tool, you can avoid errors and save time in your calculations.

How the converter uses the 25.4 formula

The inches to mm converter works by using a simple formula. One inch equals 25.4 millimetres. You just input the value in inches, and the calculator does the rest. You can even choose how many decimal places you want in your results, ensuring precision for your needs.

Customisable precision and quick reference table

Easy-to-use interface for quick conversions.
Customisable decimal precision from 0 to 4 places.
Option to display the conversion formula for better understanding.
Includes a table of common inch to millimetre values for quick reference.

Understanding Measurement Systems

Measurements differ across the globe. In the United States, inches are the norm, while most other countries favour the metric system with millimetres. Knowing how to convert between these systems is essential for anyone working internationally or in diverse industries.

Applications for This Converter

This converter is useful in many scenarios. It aids in:

Engineering: Ensuring that parts fit together correctly.
Construction: Sizing materials accurately for building projects.
Manufacturing: Specifying precise dimensions for components.
Electronics: Adjusting measurements for circuit boards.

Common Values to Know

If you often work with specific measurements, you might find these common conversions useful:

1/4" is 6.35 mm.
1/2" is 12.7 mm.
1" is 25.4 mm.
12" (1 foot) is 304.8 mm.

The formula: inches multiplied by 25.4

The formula for converting inches to millimetres is straightforward: multiply the number of inches by 25.4. This means if you have 2 inches, you would calculate 2 x 25.4 to get 50.8 millimetres. This calculator can do that for you automatically, saving time and hassle.

Enter your value and get instant results

To begin using the inches to mm converter, just enter the value you wish to convert. Choose inches or millimetres from the dropdown menus, and your result will appear in seconds. It’s that simple! Whether you’re planning a project or just curious, this tool is a reliable resource.