Inches to Millimeters Converter (in to mm)

Convert inches to millimeters instantly. You can also swap units.

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Conversion Formula

millimeters = inches ร— 25.4

1 inch = 25.4 millimeters

What Is an Inch?

An inch (in) is an imperial unit of length commonly used in the United States, United Kingdom, and Canada. It is widely used for screen sizes, tools, hardware, and everyday measurements.

What Is a Millimeter?

A millimeter (mm) is a metric unit of length equal to one thousandth of a meter. It is commonly used in engineering, manufacturing, medicine, and precision measurements.

How to Convert Inches to Millimeters

  1. Take the length in inches.
  2. Multiply it by 25.4.
  3. The result is the length in millimeters.

Example: 4 in ร— 25.4 = 101.6 mm

Inches to Millimeters Key Values Table

Inches (in)Millimeters (mm)
125.4
250.8
376.2
4101.6
5127
6152.4
8203.2
10254
12304.8
20508

Examples

2 inches = 50.8 millimeters

5 inches = 127 millimeters

12 inches = 304.8 millimeters

Frequently Asked Questions

How many millimeters are in 1 inch?

There are exactly 25.4 millimeters in one inch.

Why is 25.4 used?

Because one inch is internationally defined as exactly 25.4 millimeters.

Is this conversion exact?

Yes. The inch-to-millimeter conversion factor is exact.

Real-Life Examples

Inches to Millimeters Visual Guide

Inches are larger units than millimeters. One inch is equal to 25.4 millimeters, meaning it contains many smaller metric units.

Quick Visual Comparison
1 inch (25.4 mm)
4 inches (101.6 mm)
Easy Mental Conversion
Download Full 1โ€“300 Inches to Millimeters Table (CSV)
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