How many millimeters are in 1 inch?

1 inch (in) equals 25.4 millimeter (mm). To convert, use the formula: mm = inches × 25.4.

What is the formula to convert inch to millimeter?

The formula is: mm = inches × 25.4. For example, 5 in = 127 mm. To convert back: inches = mm ÷ 25.4.

How do I convert 5 inch to millimeter?

5 inch = 127 millimeter. Using the formula mm = inches × 25.4: 5 in = 127 mm.

How many inches are in 1 millimeter?

1 millimeter (mm) equals 0.0394 inch (in). This is the reverse conversion: inches = mm ÷ 25.4.

Is the inch to millimeter conversion exact?

The conversion factor is precise to multiple decimal places. 1 in = 25.4 mm. This calculator uses the internationally recognized conversion factors for accuracy.

When would I need to convert inch to millimeter?

Common use cases include precision engineering, 3D printing, CNC machining, pipe and bolt sizing. This conversion is frequently needed when working with measurements across different unit systems.

How do I share my inch to millimeter conversion?

The URL updates automatically as you enter values. Copy the URL from your browser or click the Share button to share your exact conversion. The recipient will see the same values when they open the link.

Inches to Millimeters Converter

Enter Length

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 in	25.4 mm
2 in	50.8 mm
5 in	127 mm
10 in	254 mm
25 in	635 mm
50 in	1,270 mm
100 in	2,540 mm
250 in	6,350 mm
500 in	12,700 mm
1,000 in	25,400 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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