Millimeters to Inches
One millimeter equals 0.03937 inches.
Inches = millimeters ÷ 25.4
By Piero Nanni · Last checked
Millimeters to Inches Calculator
1 Millimeters = 0.03937008 Inches
How to Convert Millimeters to Inches
Formula:
Inches = millimeters ÷ 25.4
Worked example:
12 millimeters ÷ 25.4 = 0.4724 inches
Millimeters to Inches Conversion Table
| mm | in |
|---|---|
| 1 | 0.0394 |
| 1.5 | 0.0591 |
| 2 | 0.0787 |
| 2.5 | 0.0984 |
| 3 | 0.1181 |
| 4 | 0.1575 |
| 5 | 0.1969 |
| 6 | 0.2362 |
| 7 | 0.2756 |
| 7.5 | 0.2953 |
| 8 | 0.315 |
| 9 | 0.3543 |
| 10 | 0.3937 |
| 12 | 0.4724 |
| 15 | 0.5906 |
| 20 | 0.7874 |
| 25 | 0.9843 |
| 25.4 | 1 |
| 30 | 1.1811 |
| 40 | 1.5748 |
| 50 | 1.9685 |
| 60 | 2.3622 |
| 70 | 2.7559 |
| 75 | 2.9528 |
| 80 | 3.1496 |
| 90 | 3.5433 |
| 100 | 3.937 |
| 150 | 5.9055 |
| 200 | 7.874 |
| 250 | 9.8425 |
| 300 | 11.811 |
About This Conversion
Millimeters to inches is the workshop conversion: drill bits, sheet thickness, bolt diameters, 3D printer nozzles, camera lens filters. Metric hardware is specified in whole millimeters while imperial hardware uses fractions, and the two systems interleave without ever quite lining up.
That near-miss causes real damage. A 10 mm socket is 0.3937 in and a 3/8 in socket is 9.525 mm, close enough to seat on a fastener and round it off. The only pair that is genuinely interchangeable is 25.4 mm and 1 inch, because that is the definition.
Frequently Asked Questions
How many inches is 1 mm?
One millimeter is 0.03937 inches, about 1/25 of an inch.
How many mm is 1 inch?
Exactly 25.4 millimeters.
Is a 10 mm socket the same as 3/8 inch?
No. 3/8 in is 9.525 mm against 10 mm. Using one for the other risks rounding off the fastener.
What is 5 mm in inches as a fraction?
5 mm is 0.1969 in, closest to 13/64 in and near enough to 3/16 in (0.1875 in) for rough work.