How to convert inches to millimeters
Common in engineering drawings, screen sizes, and metric fabrication. Multiply the inch value by the exact unit relationship shown below. CalcOS evaluates through the meter so this route and its inverse always share one certified definition.
mm = in × 25.4
Worked example: 3 in = 76.2 mm.
inches to millimeters conversion table
| inch (in) | millimeter (mm) |
|---|---|
| 1 | 25.4 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
Definitions and precision
The international inch, foot, yard, and mile are exact consequences of 1 inch = 0.0254 meter. Metric prefixes are exact powers of ten. Results may still display rounded decimals because many inverse relationships are repeating numbers.
Related length conversions
Sources: BIPM SI Brochure and NIST Handbook 44, Appendix C. Also see the complete Length Converter guide.