Convert millimetres to inches
Enter a value in millimetres (mm) to get inches (in). One millimetre is 0.03937 inches; one inch is 25.4 millimetres.
How to use the Millimetre to inch
- Type the number of millimetres.
- Click Convert.
- Read the result in inches, plus the same value in every other length unit.
mm to in formula
inches = millimetres × 0.03937. To go the other way, millimetres = inches × 25.4 (see inches to millimetres).
Worked example
12 mm × 0.03937 = 0.472441 in.
Millimetres to inches conversion table
| Millimetres | Inches |
|---|---|
| 0.1 mm | 0.003937 in |
| 0.5 mm | 0.019685 in |
| 1 mm | 0.03937 in |
| 2 mm | 0.07874 in |
| 3 mm | 0.11811 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.393701 in |
| 20 mm | 0.787402 in |
| 25 mm | 0.984252 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.937 in |
| 250 mm | 9.8425 in |
| 500 mm | 19.685 in |
| 1,000 mm | 39.3701 in |
About the millimetre
One thousandth of a metre. Used for engineering drawings, paper sizes and small measurements; a credit card is about 0.8 mm thick.
About the inch
Exactly 25.4 mm since the 1959 international yard and pound agreement. Screens, tyres and paper in the USA and UK are still sized in inches.
Related conversions
Frequently asked questions
How many inches in a millimetre?
0.03937 inches.
How many millimetres in a inch?
25.4 millimetres.
Is the factor exact?
The factor 0.03937 is derived from the units' exact definitions; only the display is rounded.
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Last updated 2026-09-23.