Inches to millimeters (in to mm)
Multiply inches by exactly 25.4. The common fractions convert cleanly: 1/4 inch is 6.35 mm, 1/2 inch is 12.7 mm and 3/4 inch is 19.05 mm - useful at the hardware store when a bolt is labelled one way and your spanner the other.
in to mm conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.13 | 3.18 |
| 0.25 | 6.35 |
| 0.5 | 12.7 |
| 0.75 | 19.05 |
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 6 | 152.4 |
| 12 | 304.8 |
How to convert inches to millimeters
The formula is millimeters = inches x 25.4. Type any value into the converter above for
an exact result, or use the table for the most common conversions. For other units, the
full length converter handles every combination, and
the unit converter covers length, weight, temperature,
speed, area, volume and data in one place.
Frequently asked questions
How many millimeters are in 1 inch?
1 in = 25.4 mm. The formula is millimeters = inches x 25.4; the converter applies it to whatever you type and rounds only for display.
What is 2 in in mm?
2 in = 50.8 mm, using millimeters = inches x 25.4.
How do I convert millimeters back to inches?
Use inches = millimeters ÷ 25.4. For example, 20 mm = 0.787 in. The mm to in converter does this for you.