How to convert inches to millimeters
To convert inches to millimeters, multiply the value by the conversion factor 25.4. To go the other way, multiply by 0.0393700787 (or divide by 25.4).
Worked example: 25 in to mm
- Write the value: 25 in
- Multiply by 25.4: 25 × 25.4
- Result: 635 mm
Inch to Millimeter conversion table
Quick reference values, rounded to 6 significant digits.
| Inch (in) | Millimeter (mm) |
|---|---|
| 0.1 in | 2.54 mm |
| 0.25 in | 6.35 mm |
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127 mm |
| 6 in | 152.4 mm |
| 7 in | 177.8 mm |
| 8 in | 203.2 mm |
| 9 in | 228.6 mm |
| 10 in | 254 mm |
| 12 in | 304.8 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 30 in | 762 mm |
| 40 in | 1,016 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 |
Millimeter to Inch
| mm | in |
|---|---|
| 1 mm | 0.0393701 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.393701 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.93701 in |
1 Inch in other length units
About Inch and Millimeter
What is a inch (in)?
An inch is exactly 2.54 centimeters. Inches are used for screen sizes, pipes, tyres, paper and body measurements.
What is a millimeter (mm)?
A millimeter is one thousandth of a meter, used for precise measurements such as rainfall, engineering drawings, screws and phone thickness.
Where inch to millimeter conversion is used
Length conversions are needed for measuring height, furniture, rooms, travel distances, screen sizes, fabric and construction materials. Converting between inches and millimeters is especially common when you compare products, read foreign specifications, or fill in forms that expect a specific unit.
Need every unit at once? Use the full Length Converter.
Frequently asked questions
How many millimeters are in 1 inch?
1 Inch equals 25.4 mm.
How do I convert inches to millimeters?
Multiply the number of inches by 25.4. For example, 25 in × 25.4 = 635 mm.
What is 25 in in mm?
25 in = 635 mm.
How many inches are in 1 millimeter?
1 Millimeter equals 0.0393701 in. Use the MM to Inch converter for the reverse direction.
Is this Inch to Millimeter converter accurate?
Yes. It uses exact internationally defined conversion factors, calculated with full floating-point precision. Results are displayed rounded for readability.