inches to mm Converter
1 in = 25.4 mm. Enter a value. The result updates immediately.
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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
- Enter the value in inches.
- Select inches as the source unit.
- Select mm as the target unit.
- Read or copy the result.
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.