We measure everything, from the length of a room to the size of a screw. And depending on where you are in the world, you’re likely using either the metric system (millimeters) or the imperial/US customary system (inches).
Maybe you need to figure out how many inches 6.3mm is. Or maybe you need to know the reverse! Whatever your reason, this article is your guide to converting between millimeters and inches.
We’ll cover the definitions of each unit, the conversion formula, how to deal with fractional inches, and some practical applications of these conversions.
Understanding Millimeters (mm)
Let’s break down what a millimeter actually is. A millimeter (mm) is a unit of length in the metric system. If you took one meter and divided it into 1000 equal parts, each of those tiny parts would be a millimeter.
Millimeters are part of a larger system. You’ve probably also heard of centimeters (cm). There are 10 millimeters in every centimeter. So, millimeters are even smaller than those!
Millimeters are useful for measuring small things. You’ll see them used in technical drawings, photography (for lens sizes, for example), and for measuring small objects. For context, a U.S. dime is about 1.35 mm thick. So, 6.3 mm isn’t very much at all!
Understanding Inches
An “inch” is a unit of length in the imperial and U.S. customary measurement systems.
Think of it this way:
- 12 inches equals 1 foot.
- 36 inches equals 1 yard.
Inches are extremely common in the United States. You’ll hear people use inches to measure all kinds of things.
For example, you might use inches to measure the size of a TV screen, the diameter of a pipe, or the length of a piece of furniture.
Millimeters to Inches: The Conversion Factor
To convert from millimeters to inches, you need to know the conversion factor. Here it is:
1 inch = 25.4 millimeters
To convert millimeters to inches, you divide the number of millimeters by 25.4. The formula looks like this:
inches = millimeters ÷ 25.4
So, let’s convert 6.3mm to inches:
6. 3mm / 25.4 = 0.248 inches (approximately)
Because we rounded the answer, this conversion is approximate. Depending on your needs, you may need to use more decimal places to achieve a greater level of precision.
How to convert millimeters to inches
If you want to convert millimeters to inches, you need to divide the millimeter value by 25.4. The formula looks like this:
inches = millimeters / 25.4
For instance, if you want to convert 10 mm to inches, you would perform the following calculation:
10 mm / 25.4 = 0.3937 inches
Or, to convert 50 mm to inches:
50 mm / 25.4 = 1.9685 inches
Keep in mind that when you’re performing these calculations, you may need to consider significant figures and rounding to get the most accurate result.
Converting millimeters to fractional inches
Sometimes, you need a measurement in fractional inches, like you’d find on a ruler. Here’s how to convert millimeters to fractional inches.
Understanding fractional inches
Inches are often expressed as fractions, such as 1/2, 1/4, 1/8, 1/16, 1/32, and 1/64. The denominator of the fraction indicates the precision of the measurement. For example, 1/2 inch is less precise than 1/64 inch.
Converting to fractional inches involves approximating the decimal inch value to the nearest fraction.
Converting and rounding to fractional inches
To convert millimeters to fractional inches, use the methods described above to convert to decimal inches. Then:
- Figure out the level of precision you need (1/16, 1/32, 1/64, etc.).
- Multiply your decimal inch value by the denominator of your desired fraction.
- Round to the nearest whole number.
- Place that number over the denominator you chose.
- Simplify the fraction if possible.
For example, say you’ve converted 6.3 mm to 0.248 inches, and you want to convert that to the nearest 1/16th of an inch.
Multiply 0.248 by 16, which gives you 3.97. Round that to 4. So, 0.248 inches is approximately 4/16 inches, which simplifies to 1/4 inch.
If you needed greater precision, you could follow the same steps with 1/32 or 1/64. Just remember that the more precise you are, the more cumbersome the fraction becomes. It’s important to choose the right level of precision for your particular application.
When do you need to convert millimeters to inches?
Converting between millimeters and inches comes in handy in lots of situations. You might need it for DIY projects around the house, woodworking, engineering plans, or even manufacturing processes. Basically, anytime you’re working with measurements from different systems, you’ll probably have to do a conversion.
Luckily, there are tons of tools to help you out. You can use online converters, calculators, or even just a ruler or tape measure. Online converters are especially useful because they’re fast and accurate.
Frequently Asked Questions
Is 5/16 the same as 6mm?
Not exactly, but it’s close! 5/16 of an inch is approximately equal to 7.94mm. So, while it’s not a direct equivalent to 6mm, it’s often used interchangeably in situations where precision isn’t critical. Always double-check the required measurement for your specific application.
How many mm is 1/8 inch?
One-eighth (1/8) of an inch is equal to 3.175 millimeters. This is a common conversion to know, especially when working with smaller measurements or needing to convert between imperial and metric systems. Remember that 1 inch is exactly 25.4 millimeters, making the math relatively straightforward.
What size is 6.3 mm?
6.3mm is approximately equivalent to 1/4 inch (0.248 inches to be precise). This is a fairly standard measurement, and understanding its imperial equivalent can be helpful depending on the context. You’ll often encounter 6.3mm in applications where both metric and imperial measurements are used.
Putting It All Together
Knowing how to convert millimeters to inches — and inches to millimeters — is essential in many fields. Remember the formula: 1 mm = 0.03937 inches. You can use this figure to convert to decimal inches. Or, for greater precision, you can convert to fractional inches.
With this information, you’re well-equipped to make accurate and efficient conversions between metric and imperial units.