Convert millimeters to inches instantly. Enter a value below, or use the formula and reference table further down the page.
In practice
Millimetres to inches divides by 25.4, because an inch is defined as exactly 25.4 mm. It is used for camera lenses and sensors, bolt and bit sizes, jewellery, and rainfall or snowfall measurements. A few anchors help: 25 mm is just under an inch, 10 mm is about 3/8 inch, and 6 mm is about 1/4 inch. Because decimals of an inch are awkward to read on a tape measure, the next step is usually to round to the nearest 1/16 or 1/32 inch.
How to convert millimeters to inches
Multiply the value by 0.03937007874.
in = mm × 0.03937007874Example: 10 mm = 0.3937 in.
Millimeters to Inches conversion table
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 mm | 0.0394 in |
| 2 mm | 0.0787 in |
| 3 mm | 0.1181 in |
| 4 mm | 0.1575 in |
| 5 mm | 0.1969 in |
| 10 mm | 0.3937 in |
| 15 mm | 0.5906 in |
| 20 mm | 0.7874 in |
| 25 mm | 0.9843 in |
| 50 mm | 1.9685 in |
| 100 mm | 3.937 in |
Frequently asked questions
How many inches is 1 millimeter?
1 millimeter equals 0.0394 inches.
What is the formula to convert mm to in?
To convert mm to in, multiply the value by 0.03937007874. The full formula is: in = mm × 0.03937007874.
How do I convert inches back to millimeters?
Use the same calculator above and type your value into the inches field instead — it converts in both directions. Or use the reverse formula: mm = in ÷ 0.03937007874.
Is the mm to in conversion exact?
The conversion factor used here (0.03937007874) is the standard internationally defined value. Results on this page are rounded to four decimal places for readability.