Millimeters and inches are two common ways to measure length, but one is part of the metric system, and the other is part of the imperial system. Being able to convert between them is essential in fields like engineering, manufacturing, and even for DIY projects around the house.
That’s why we’ve put together this guide, complete with a millimeter inches conversion chart, to help you easily switch between these two units of measurement. We’ll also break down the math behind the conversion so you can do it yourself.
Understanding millimeters and inches
If you’re like me, you sometimes get millimeters and inches mixed up. Here’s a quick guide to these two common units of measurement.
What’s a millimeter?
A millimeter (mm) is a metric unit of length. One millimeter is 1/1000th of a meter. Millimeters are commonly used in countries that use the metric system.
What’s an inch?
An inch (in) is a unit of length in the imperial and U.S. customary measurement systems. An inch is 1/12 of a foot, or 1/36 of a yard.
One inch equals 2.54 centimeters.
How to convert millimeters to inches
Want to convert from millimeters to inches? It’s easy! Here’s the formula:
inches = millimeters ÷ 25.4
The number 25.4 is the conversion factor because there are exactly 25.4 millimeters in one inch. For example, to convert 50 millimeters to inches:
50 mm / 25.4 = 1.9685 inches
Millimeter to Inch Conversion Chart
Need to convert millimeters to inches? Here’s a handy chart with some common conversions. Keep in mind that while we’ve included fractional inch equivalents, these are approximations.
Decimal Inch Equivalents
- 1 mm = 0.03937 inches
- 2 mm = 0.07874 inches
- 10 mm = 0.39370 inches
- 25 mm = 0.98425 inches
- 25.4 mm = 1 inch
Here’s a more extensive table demonstrating the conversion from 1mm to 50mm:
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.03937 |
| 2 | 0.07874 |
| 3 | 0.11811 |
| 4 | 0.15748 |
| 5 | 0.19685 |
| 6 | 0.23622 |
| 7 | 0.27559 |
| 8 | 0.31496 |
| 9 | 0.35433 |
| 10 | 0.39370 |
| 11 | 0.43307 |
| 12 | 0.47244 |
| 13 | 0.51181 |
| 14 | 0.55118 |
| 15 | 0.59055 |
| 16 | 0.62992 |
| 17 | 0.66929 |
| 18 | 0.70866 |
| 19 | 0.74803 |
| 20 | 0.78740 |
| 21 | 0.82677 |
| 22 | 0.86614 |
| 23 | 0.90551 |
| 24 | 0.94488 |
| 25 | 0.98425 |
| 26 | 1.02362 |
| 27 | 1.06299 |
| 28 | 1.10236 |
| 29 | 1.14173 |
| 30 | 1.18110 |
| 31 | 1.22047 |
| 32 | 1.25984 |
| 33 | 1.29921 |
| 34 | 1.33858 |
| 35 | 1.37795 |
| 36 | 1.41732 |
| 37 | 1.45669 |
| 38 | 1.49606 |
| 39 | 1.53543 |
| 40 | 1.57480 |
| 41 | 1.61417 |
| 42 | 1.65354 |
| 43 | 1.69291 |
| 44 | 1.73228 |
| 45 | 1.77165 |
| 46 | 1.81102 |
| 47 | 1.85039 |
| 48 | 1.88976 |
| 49 | 1.92913 |
| 50 | 1.96850 |
Fractional Inch Equivalents (Approximations)
- 1 mm ≈ 3/64″
To find the approximate fractional equivalent, multiply the decimal part by the denominator you want (e.g., 16 for 1/16″). For example, if the decimal is 0.15625 inches, then 0.15625 16 = 2.5, which rounds to 2/16 or 1/8 inch.
How to Convert Millimeters to Fractional Inches
To convert from millimeters to fractional inches, first convert to decimal inches by dividing your millimeter measurement by 25.4.
Inches = Millimeters / 25.4
The next step depends on the level of precision you need. For example, to convert to the nearest 1/16th of an inch, multiply the decimal portion of your result by 16. Then round to the nearest whole number to get your numerator.
Example: Convert 100 mm to the nearest 1/16th of an inch.
100 mm / 25.4 = 3.937 inches.
0. 937 16 = 14.992 ≈ 15
100 mm ≈ 3 15/16 inches.
Frequently Asked Questions
How do you convert mm to inches chart?
A mm to inches conversion chart provides a quick and easy way to find the equivalent inch value for a given measurement in millimeters. To use one, simply locate the millimeter value you want to convert and read the corresponding inch value from the chart. Remember, these charts often provide approximations, so for precise conversions, it’s best to use a calculator or online converter.
Is 40 mm one inch?
No, 40 mm is not one inch. One inch is equal to 25.4 millimeters. Therefore, 40 millimeters is approximately 1.57 inches. To get an exact conversion, divide 40 by 25.4. It’s a common mistake, so always double-check your conversions!
Is 7 mm the same as 1/4 inch?
No, 7 mm is not exactly the same as 1/4 inch. One-quarter of an inch (1/4″) is equal to 6.35 millimeters. Therefore, 7 mm is slightly larger than 1/4 inch. While the difference might seem small, it can be significant in applications requiring precise measurements.
Putting It All Together
Knowing how to convert millimeters to inches accurately is important in many fields and everyday situations.
You can use the formula: inches = millimeters ÷ 25.4. Or, for a quick reference, you can use a millimeter to inch conversion chart.
Whether you’re working on a DIY project, doing engineering work, or just need to know the equivalent, you now have the tools to make accurate conversions between millimeters and inches.