Convert Millimeter to Inch.
Input the value of millimeters below to convert instantly to inches with standard conversions, definitions, and equations.
About converting millimeters to inches
Millimeters to inches is the precision conversion — used in engineering, manufacturing, and DIY where metric drawings meet imperial tools and hardware.
There are exactly 25.4 millimeters in an inch, so to convert millimeters to inches you divide by 25.4. A 10 mm bolt is 0.3937 inches, and a 50 mm bracket is 1.9685 inches. Because hardware is often sold in one system but installed in another, this is one of the most common conversions in workshops and on construction sites.
Millimeters are the preferred unit on technical drawings worldwide because they avoid decimals for small parts — 3.5 mm reads more cleanly than 0.138 inches. When those drawings reach an imperial-tooled shop, the millimeter-to-inch conversion is what lets a machinist pick the right drill bit or tap.
- Common shop equivalents worth memorizing: 25.4 mm = 1 inch, 12.7 mm = 1/2 inch, 6.35 mm = 1/4 inch.
- When matching drill bits, round to the nearest available fractional or number bit rather than the exact decimal.
How to Convert Millimeters to Inches
To convert millimeter to inch, we use the official conversion formulas. Below is the mathematical formula, plain-English explanation, and a worked example.
Millimeter (mm)
One-thousandth of a meter. Common metric unit for small lengths.
Inch (in)
Imperial and US customary unit equal to exactly 2.54 centimeters.
Millimeter to Inch Conversion Table
| Millimeter (mm) | Inch (in) |
|---|---|
| 1 mm | 0.03937 in |
| 2 mm | 0.07874 in |
| 3 mm | 0.11811 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.3937 in |
| 15 mm | 0.59055 in |
| 20 mm | 0.7874 in |
| 25 mm | 0.98425 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.93701 in |
| 250 mm | 9.84252 in |
| 500 mm | 19.68504 in |
| 1000 mm | 39.37008 in |
Inch to Millimeter Conversion Table
| Inch (in) | Millimeter (mm) |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1270 mm |
| 100 in | 2540 mm |
| 250 in | 6350 mm |
| 500 in | 12700 mm |
| 1000 in | 25400 mm |