How it's calculated
in = mm ÷ 25.4 (reverse: mm = in × 25.4)
mm = millimetres, in = inches; 1 inch = 25.4 mm exactly.
Common values
| Millimetres | Inches |
|---|---|
| 1 | 0.03937 |
| 10 | 0.3937 |
| 25.4 | 1 |
| 100 | 3.93701 |
Common questions
How many millimetres are in an inch?
Exactly 25.4 millimetres. This is a defined value, not a rounded one.
How do I convert mm to inches by hand?
Divide the millimetre value by 25.4. For example, 50 mm divided by 25.4 is about 1.97 inches.