How to convert millimeters to inches
One inch is exactly 25.4 millimeters. To turn millimeters into inches, divide by 25.4. Small parts, drill bits, screws and paper are often measured in millimeters in one country and inches in another.
Formula: inches = mm ÷ 25.4
Example: 10 mm ÷ 25.4 = 0.394 inches (just over 3/8 in)
mm to in table
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.039 |
| 2 | 0.079 |
| 3 | 0.118 |
| 4 | 0.157 |
| 5 | 0.197 |
| 6 | 0.236 |
| 8 | 0.315 |
| 10 | 0.394 |
| 12 | 0.472 |
| 13 | 0.512 |
| 15 | 0.591 |
| 16 | 0.63 |
| 19 | 0.748 |
| 20 | 0.787 |
| 22 | 0.866 |
| 25 | 0.984 |
| 25.4 | 1 |
| 30 | 1.181 |
| 40 | 1.575 |
| 50 | 1.969 |
| 75 | 2.953 |
| 100 | 3.937 |
Values are rounded to 3 decimal places.
Close inch fractions
- 3 mm ≈ 1/8 in (0.125)
- 6 mm ≈ 1/4 in (0.25)
- 10 mm ≈ 3/8 in (0.375)
- 13 mm ≈ 1/2 in (0.5)
- 19 mm ≈ 3/4 in (0.75)
- These are close, not equal — for a snug fit (a wrench on a bolt), use the right system
How to use it
- Type a number in the From box — the answer appears straight away
- Click Swap (⇄) to convert the other way, from inches to millimeters
- Change the units or the category to convert anything else — length, weight, temperature, volume, speed and more
Frequently asked questions
How many mm are in an inch?
Exactly 25.4 millimeters.
Is 10 mm the same as 3/8 inch?
Almost. 10 mm is 0.394 inches and 3/8 inch is 0.375 inches — about half a millimeter apart. Close enough for most things, but not for a tight-fitting wrench.
How do I convert mm to cm?
Divide by 10: 25 mm = 2.5 cm.
Is my data sent anywhere?
No. The conversion runs in your browser, on your own device.
Related tools
- Unit Converter — every unit in one place
