Length · in → mm
Inches to Millimetres
Enter any value below to convert inches to millimetres instantly.
To
1 in = 25.4 mm
Conversion formula
How to convert in to mm
mm = in × 25.4
Multiply the inches value by 25.4 to get millimetres. The converter keeps extra precision internally and rounds only the displayed answer.
Converting inches to millimetres is useful when comparing dimensions, travel distances, building measurements or product specifications written in different measurement systems.
Worked example
Convert 10 in10 in = 254 mm
Calculated with the published formula. No estimated exchange rates or hidden rounding.
Common inches to millimetres values
| Inches (in) | Millimetres (mm) |
|---|---|
| 1 in | 25.4 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 100 in | 2,540 mm |
Quick answer
How many millimetres are in one inche?
One inche equals 25.4 mm.