Convert Inches to millimeters
1 inch = 25.4 millimeters · mm = in × 25.4
When you need this conversion
This conversion goes from inches, the US customary unit for screens, hardware, and short measurements, to millimeters, the metric unit used for hardware, engineering drawings, and anything needing sub-centimeter precision. Both measure the same physical quantity, so the conversion is exact — the difference is which unit your source, tool, or region happens to use.
Inches to millimeters conversion table
| Inches (in) | Millimeters (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 | 1,270 mm |
| 75 in | 1,905 mm |
| 100 in | 2,540 mm |
| 250 in | 6,350 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
The formula
mm = in × 25.4Because both units measure length, the conversion is a single multiplication by a fixed factor. That factor never changes, so the result is exact.
Convert the other way
Millimeters to inches →Related length conversions
- Inches to centimeters
- Micrometers to millimeters
- Millimeters to micrometers
- Centimeters to inches
- Centimeters to feet
- Meters to kilometers
- Kilometers to meters
- Feet to centimeters
- Feet to yards
- Yards to feet
- Centimeters to millimeters
- Meters to millimeters
Frequently asked questions
- How many millimeters are in a inch?
- There are 25.4 millimeters in 1 inch. The formula is mm = in × 25.4.
- How do you convert inches to millimeters?
- Use the formula mm = in × 25.4. For example, 10 inches equals 254 millimeters.
- Is the inches to millimeters conversion exact?
- Yes. Inches and millimeters are both units of length, related by an exact defined factor. Displayed results are rounded for readability.
- What is in short for?
- in is the standard symbol for inch (also written as in). mm is the symbol for millimeter.