Formula to convert Inch to Millimeter
Millimeters = Inches × 25.4
Example
Convert 4 inches to millimeters:
4 × 25.4 = 101.6 mm
Conversion Table
| Inches | Millimeters |
|---|---|
| 1 | 25.40 |
| 5 | 127.00 |
| 10 | 254.00 |
| 20 | 508.00 |
| 100 | 2540.00 |
Frequently Asked Questions (FAQ)
How many millimeters are in an inch?
There are exactly 25.4 millimeters in one inch. This is an international standard used in engineering and manufacturing worldwide.
How do I convert inches to mm manually?
To convert inches to millimeters, multiply the number of inches by 25.4. For example, if you have 2 inches: 2 × 25.4 = 50.8 mm.
Is 1/8 inch equal to 3 mm?
Not exactly. 1/8 of an inch is equal to 3.175 mm. While 3 mm is a common nearby metric size, the difference is important for precision tools and machinery.
About the Inch (in)
The inch (symbol: in or ″) is a unit of length in the Imperial and US Customary systems. Since 1959, the inch has been defined as exactly 25.4 millimeters. It is the primary small unit of measure in the United States and is widely used in the UK and Canada.
The inch is unique because it is often divided into fractions rather than decimals. In construction, woodworking, and plumbing, measurements like 3/4" or 5/8" are standard. It is also the universal unit for measuring the diameter of wheels, pipes, and the screen size of televisions and smartphones.
About the Millimeter (mm)
The millimeter (symbol: mm) is a unit of length in the International System of Units (SI), representing one-thousandth of a meter. It is the go-to unit for any task requiring high precision.
Because the millimeter is so small (about the thickness of a paperclip wire), it allows engineers and architects to provide exact specifications without using fractions. In the metric system, 10 millimeters make up one centimeter. It is the standard unit for mechanical parts, scientific instruments, and measuring rainfall in most parts of the world.