Length
inches to mm Converter
1 in = 25.4 mm. Enter any value and the result updates instantly.
Convert
Accuracy and rounding
Use the decimal result for specifications. For tape measures, round only after you know the tolerance you need.
Inches and mm are tied back to the SI meter through fixed definitions, so the underlying conversion factor is stable.
For cutting, fitting, drawings, and product specs, keep extra decimals in mm and round only at the final step.
How to convert inches to mm
- Type the inches value in the calculator.
- Keep inches selected as the from unit and mm selected as the to unit.
- Use the instant result, or copy it with the copy button.
inches to mm chart
| inches | mm |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 100 in | 2,540 mm |
Formula
mm = in x 25.4
Example: 1 in = 25.4 mm.
Source
SI meter definitions and exact international inch, foot, yard, and mile relationships.
Common questions
How do I convert inches to mm?
Enter the inches value in the converter, or multiply by the factor shown in the formula. 1 in = 25.4 mm.
What should I watch out for?
Round only after converting if the measurement is used for cutting, fitting, or specifications.
Where does this length conversion come from?
SI meter definitions and exact international inch, foot, yard, and mile relationships. ConverterBase uses stable definitions and fixed conversion factors, not live or rounded market data.