Millimeters to Inches
Type millimeters (mm), see inches (in).
By Akash Yadav Updated 27 September 2026
Type a number above to see the answer.
Or tap a number:
The formula
How to convert millimeters to inches
To change millimeters into inches, divide by 25.4.
inches = millimeters ÷ 25.4
Going the other way: millimeters = inches × 25.4
1 millimeter = 0.03937008 inches. This factor does not end, so results on this page are rounded.
Worked example
You have 10 millimeters. Divide by 25.4. 10 ÷ 25.4 = 0.3937 in.
Common values
Millimeters to inches conversion table
| Millimeters (mm) | Inches (in) |
|---|---|
| 0.5 mm | 0.0197 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 |
| 6 mm | 0.2362 in |
| 8 mm | 0.315 in |
| 10 mm | 0.3937 in |
| 12 mm | 0.4724 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 |
Before you rely on it
Decimal inches, not fractions
1 inch is exactly 25.4 mm, so millimeters to inches is divide by 25.4. The answer is a decimal, and because 1/25.4 never ends, it is rounded.
Tape measures, drill bits and wrenches in the US are marked in fractions: 1/16, 1/8, 1/4 inch. To match a decimal answer to a fraction, multiply the decimal part by 16 and round: 10 mm is about 0.394 in, and 0.394 × 16 ≈ 6.3, so it is just over 6/16, or 3/8 inch.
Metric and imperial tools that look close are not interchangeable. A 10 mm socket and a 3/8 inch (9.525 mm) socket differ by about half a millimeter, enough to round off a bolt head.
Rainfall is reported in millimeters in most countries and inches in the US. 25 mm of rain is a little under an inch; 1 inch is 25.4 mm.
Common questions
Frequently asked questions
How many inches is 1 mm?
1 mm is about 0.0394 inches — roughly 1/25 of an inch.
How many inches is 10 mm?
10 mm (1 cm) is about 0.3937 inches — a little over 3/8 inch.
How many inches is 5 mm?
5 mm is about 0.1969 inches — a little over 3/16 inch.
How many inches is 20 mm?
20 mm is about 0.7874 inches.
How many inches is 50 mm?
50 mm is about 1.9685 inches — just under 2 inches.
How many mm are in an inch?
1 inch is exactly 25.4 mm.
Keep going
Related converters
- Inches to Millimeters in → mm
- Centimeters to Inches cm → in
- Inches to Centimeters in → cm
- All length converters
Every factor on this page is listed in our conversion methodology.