Inches to Millimeters Converter
Convert inches (in) to millimeters (mm) instantly. Type a value above and the result updates while you type. 1 inch equals 25.4 millimeters.
Result updates as you type. Values are calculated locally in your browser — nothing is sent to a server.
The formula
1 inch = 25.4 millimeters
Multiply the inches value by 25.4 to get millimeters. Or divide by 0.03937 to go the other way.
Inches to millimeters conversion table
| in | mm |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127 |
| 6 | 152.4 |
| 7 | 177.8 |
| 8 | 203.2 |
| 9 | 228.6 |
| 10 | 254 |
| 15 | 381 |
| 20 | 508 |
| 25 | 635 |
| 50 | 1270 |
| 75 | 1905 |
| 100 | 2540 |
Worked examples
- 0.5 in × 25.4 = 12.7 mm
- 6 in × 25.4 = 152.4 mm
- 12 in × 25.4 = 304.8 mm
Conversion factors follow the exact international definitions (SI/BIPM; imperial units per the 1959 International Yard and Pound Agreement, maintained by NIST). NIST unit conversion reference
Factors last verified August 2026 · Built by Jeffrey Tepper.
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Frequently asked questions
How many millimeters are in 1 inch?
1 inch equals 25.4 millimeters (in → mm).
How do you convert inches to millimeters?
Multiply the number of inches by 25.4. For example: 10 in × 25.4 = 254 mm.
What is 50 in in mm?
50 in equals 1270 mm.
Which is bigger: 1 inch or 1 millimeter?
1 inch is bigger: it equals 25.4 millimeters.