CloudCalcAppMillimeters to Inches Converter
Convert millimeters to inches accurately. 1 inch equals exactly 25.4 millimeters, so 1 millimeter is approximately 0.0394 inches - enter a length in millimeters below to get the equivalent in inches.
Quick answer
Formula
inches = millimeters ÷ 25.4
Quick mental-math estimate
Worked Example: Convert 10 mm to Inches
- Given1 inch = 25.4 millimeters, exactly.
- Formulainches = millimeters ÷ 25.4
- Substituteinches = 10 ÷ 25.4
- Answer10 millimeters approximately equals 0.3937 inches.
Quick Examples
1 mm approximately equals 0.0394 in
1 mm ≈ 0.0394 in.
5 mm approximately equals 0.1969 in
5 mm ≈ 0.1969 in.
12 mm approximately equals 0.4724 in
12 mm ≈ 0.4724 in - see the Detailed Worked Example above for how 10 mm is calculated step by step.
25.4 mm = 1 in
25.4 mm = 1 in - the exact definition this converter uses.
50 mm approximately equals 1.9685 in
50 mm ≈ 1.9685 in.
100 mm approximately equals 3.937 in
100 mm ≈ 3.937 in.
Conversion Table
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.0394 |
| 2 | 0.0787 |
| 3 | 0.1181 |
| 5 | 0.1969 |
| 6 | 0.2362 |
| 8 | 0.315 |
| 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 |
| 75 | 2.9528 |
| 100 | 3.937 |
Millimeters to Nearest Fractional Inch
The exact decimal-inch result is shown in the calculator and table above. This reference rounds that value to the nearest 1/16 inch - a common general-purpose precision, not an exact equivalent.
| Millimeters (mm) | Inches (in) | Nearest 1/16 Inch |
|---|---|---|
| 1 | 0.0394 | 1/16 in |
| 2 | 0.0787 | 1/16 in |
| 3 | 0.1181 | 1/8 in |
| 5 | 0.1969 | 3/16 in |
| 6 | 0.2362 | 1/4 in |
| 8 | 0.315 | 5/16 in |
| 10 | 0.3937 | 3/8 in |
| 12 | 0.4724 | 1/2 in |
| 15 | 0.5906 | 9/16 in |
| 20 | 0.7874 | 13/16 in |
| 25 | 0.9843 | 1 in |
Unit Definitions
Millimeters (mm)
One thousandth of a meter - the smallest metric length unit in common everyday use.
metric system
- Machining and engineering tolerances
- Paper and material thickness
- Rainfall measurement
Inches (in)
A US customary and imperial unit equal to exactly 2.54 centimeters.
imperial system
- Screen and display sizes
- Woodworking and construction
- Paper sizes and printing
FAQ
How do you convert millimeters to inches?
Divide the length in millimeters by 25.4. For example, 50 mm ÷ 25.4 ≈ 1.9685 inches.
How many inches are in 1 millimeter?
1 millimeter is approximately 0.0394 inches.
Is a fractional-inch conversion like 3/8 in exact?
No. A fractional-inch approximation (e.g. the nearest 1/16 inch shown in the reference below) is a rounded reference, not a second exact conversion - only the decimal-inch result from dividing by 25.4 is exact to the calculator's own precision. 3/8 in itself equals exactly 9.525 mm, which is a different, more precise number than a metric value merely rounded near it.
Is 25.4 mm exactly 1 inch?
Yes. The international inch has been defined as exactly 25.4 millimeters since 1959, so this conversion is exact, not a rounded approximation.
When are millimeters and inches commonly converted?
This comes up when working with precision parts, tools, or drawings specified in millimeters that need to be compared against inch-based specifications, or vice versa.
Displayed results are rounded to a maximum of 4 decimal places for readability (extended only in the rare case a nonzero value would otherwise display as “0”), and whole-number results are shown without unnecessary decimals. The conversion factor and formula above are the exact relationship - only the calculator's displayed output is rounded.
Need a different unit? Length Converter supports many other unit conversions.