inches to mm | Exact Decimal + Formula
1 Inch = 25.4 Millimeter
Converting inches to millimeters is essential in machining, industrial design, and woodworking to adapt imperial measurements to global metric standards.
About Inch and Millimeter
Inch (in)
In typography, an inch is exactly 72 points or 96 CSS pixels.
Where it's used: Print dimensions and DPI (dots-per-inch) calculations.
Millimeter (mm)
In typography, a millimeter is 1/25.4 of an inch, about 2.835 points.
Where it's used: International print specifications.
Advertisement
Typography Converter
Tab Switch fieldsS SwapC Copy
Formula
mm = in × 25.399999994
To convert Inch to Millimeter, use the formula displayed above.
Pinned Favorites
No pinned converters yet. Click the star button to pin common pairs.
Recent History
Conversions you copy will be recorded here.
Advertisement
Inch to Millimeter: Quick Reference Table
| Inch | Millimeter (Decimal) | Fraction |
|---|---|---|
| 0.001 in | 0.0254 mm | - |
| 0.01 in | 0.254 mm | - |
| 0.1 in | 2.54 mm | - |
| 0.5 in | 12.7 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 | 1270 mm | - |
| 100 in | 2539.999999 mm | - |
| 250 in | 6349.999998 mm | - |
| 500 in | 12699.999997 mm | - |
| 1000 in | 25399.999994 mm | - |
in to mm Formula and Examples
Direct Formula
mm = in × 25.399999994 Inverse Formula
in = mm × 0.03937 Mental Math Shortcut
Multiply the value by roughly 25.4 to calculate the equivalent amount in your head.
Common Inch to Millimeter Calculations
Precision & Practical Use
For example, 10 in = 254 mm — roughly width of a small smartphone.
Results are computed to up to 9 decimal places. Round to the precision of your measuring instrument — for most typography applications, 2–3 significant figures are plenty.
Advertisement
Related Reading
Related Article
Precision in Construction Math Why 1/16 of an inch matters: tolerances, nominal vs. actual lumber, and how rounding errors stack across a build.
Related Article
Metric vs. Imperial Systems Which countries use which system, the exact conversion factors, and the US/UK differences that trip people up.
How to Convert Inch to Millimeter
How many millimeters are in one inch?
One Inch (in) equals 25.4 Millimeter (mm). To convert inches to millimeters, multiply the inch value by 25.4.
How do I convert Inch to Millimeter?
Multiply your inch value by 25.4 to get the result in Millimeter: mm = in × 25.4. For example, 5 in = 127 mm.
What is the formula for converting in to mm?
The conversion formula is mm = in × 25.4. Use the calculator above for any value, and see the reference table below for common inputs from 0.001 to 1000.
Is there a quick mental estimate for in to mm?
Multiply the value by roughly 25.4 to calculate the equivalent amount in your head.
Advertisement