Inches to millimeters
Type a value in inches to see it in millimeters straight away, or type in the second box to convert back.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the inches box.
- Read the result in millimeters as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
mm = in × 25.4
Multiply the value in inches by 25.4 to get millimeters.
Example
To convert 25 in to millimeters: 25 × 25.4 = 635 mm.
Conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 5 | 127 |
| 10 | 254 |
| 20 | 508 |
| 25 | 635 |
| 50 | 1,270 |
| 100 | 2,540 |
| 250 | 6,350 |
| 500 | 12,700 |
| 1,000 | 25,400 |
About the units
- Inch
- An inch is exactly 2.54 centimeters under the 1959 agreement, used for screens, tyres and pipes.
- Millimeter
- A millimeter is one thousandth of a meter, common in engineering drawings and thickness measurements.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many millimeters are in one inch?
1 in = 25.4 mm exactly.
How do I convert inches to millimeters?
Use mm = in × 25.4. For example, 25 in = 635 mm.
How many inches are in one millimeter?
1 mm = 0.0393701 in.
Are the inch, foot and mile factors exact or rounded?
They are exact by definition. Since the 1959 agreement one inch is exactly 2.54 cm, one foot 0.3048 m and one mile 1609.344 m.
What is the difference between a mile and a nautical mile?
A statute mile is 1609.344 meters and is used on roads. A nautical mile is 1852 meters and is used at sea and in aviation.