Inch to Millimeter Converter (in to mm)
1 inch = 25.4 millimeter. Millimeters measure small things such as screw sizes, camera sensors and rainfall, while inches dominate US hardware, pipe and tool sizes.
Result
0.5 in = 12.7 mm
How to convert inch to millimeter
Millimeters measure small things such as screw sizes, camera sensors and rainfall, while inches dominate US hardware, pipe and tool sizes. One inch is exactly 25.4 mm.
Formula
mm = in × 25.4
Worked example
0.5 in × 25.4 = 12.7 mm
Inch to Millimeter quick-reference table
| Inch (in) | Millimeter (mm) |
|---|---|
| 0.125 in | 3.175 mm |
| 0.25 in | 6.35 mm |
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 12 in | 304.8 mm |
Real-life examples
A 1/2 in socket wrench is 12.7 mm and a 3/4 in pipe is about 19.05 mm. Use this when a US part has to match a metric drawing.
Frequently asked questions
How many mm is 1/4 inch?
1/4 in = 0.25 in = 6.35 mm.
Is 25 mm the same as 1 inch?
Almost. 25 mm is 0.984 in, so 1 inch is 25.4 mm. The 0.4 mm difference matters for precision parts.
What is 1 inch in millimeter?
1 inch = 25.4 millimeter (in to mm).
What is the formula to convert in to mm?
mm = in × 25.4. For example, 0.5 in × 25.4 = 12.7 mm.
How do I convert mm back to in?
Use the reverse converter: 1 millimeter = 0.0393701 inch. Check: 12.7 mm converts back to 0.5 in.
Reverse conversion
Need the other direction? Millimeter to Inch converter (mm to in): 1 millimeter = 0.0393701 inch.
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