Direct conversion
Convert inch [in] to millimeter [mm] instantly with formula, examples, chart, and FAQs.
1 inch [in] = 25.4 millimeter [mm]
1 inch [in] = 25.4 millimeter [mm]
Example: 1 inch [in] equals 25.4 millimeter [mm].
Length conversions use the metre as the reference unit. Common imperial relationships are exact where standardized, such as 1 inch = 0.0254 metre and 1 foot = 0.3048 metre.
Displayed results are rounded for readability. The calculator keeps enough precision for everyday use and switches to scientific notation for very large or very small values. Last reviewed: 2026-05-21.
The inch is an imperial and US customary length unit equal to exactly 2.54 centimeters.
HistoryThe inch has older customary origins and was standardized internationally as exactly 25.4 millimeters.
Current useInches are widely used for screen sizes, construction, product dimensions, clothing, tools, and household measurements.
The millimeter is a metric length unit equal to one thousandth of a meter.
HistoryMillimeters come from the decimal metric system and are useful for precise small measurements.
Current useMillimeters are used in engineering drawings, product dimensions, machining, printing, and medicine.
| inch [in] | millimeter [mm] |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 5 | 127 |
| 10 | 254 |
| 20 | 508 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
| 1000 | 25400 |
Use this formula: 1 inch [in] = 25.4 millimeter [mm] Enter your value in the calculator and the result updates instantly.
1 inch [in] equals 25.4 millimeter [mm].
Yes. Use the swap button in the calculator or open the related reverse conversion link when it is listed on this page.