How Many Millimeters in an Inch?
Quick Answer
There are 25.4 millimeters in an inch.
1 inch = 25.4 millimeters
Understanding the Conversion
By international agreement since 1959, one inch is defined as exactly 25.4 millimeters. This exact relationship makes converting between imperial and metric length units straightforward and is fundamental to engineering and manufacturing.
Formula
1 inch = 25.4 millimeters
Common Examples
| Description | Value |
|---|---|
| A 1/4-inch drill bit | 6.35 mm |
| A 1/2-inch bolt | 12.7 mm |
| A 3/8-inch wrench | 9.525 mm |
Quick Reference Table
Use this table for quick conversions between inch and millimeters:
| inch | millimeters |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1,270 |
| 100 | 2,540 |
Frequently Asked Questions
How Many Millimeters in an Inch?
There are 25.4 millimeters in an inch. By international agreement since 1959, one inch is defined as exactly 25.4 millimeters. This exact relationship makes converting between imperial and metric length units straightforward and is fundamental to engineering and manufacturing.
What is the formula to convert inch to millimeters?
The formula is: 1 inch = 25.4 millimeters. To convert, multiply the number of inchs by 25.4 to get the equivalent in millimeters.
How do I convert millimeters to inch?
To convert millimeters to inch, divide the number of millimeters by 25.4. For example, 127 millimeters equals 5 inchs.