Whether you’re working on a DIY project or trying to figure out the size of something you’re buying online, you’ve probably needed to convert millimeters (mm) to inches (in) at some point.
The metric system is used worldwide, but in the United States, we still use the imperial system for many measurements. That makes converting between millimeters and inches a common, everyday need.
This article is a guide to understanding and converting mm to inches, with a focus on converting 39mm in inches. We’ll cover the definitions of each unit, the conversion formula, and some real-world examples.
Millimeters and inches: What’s the difference?
If you’re trying to convert millimeters to inches, it may help to know a bit more about these measurements.
What’s a millimeter?
A millimeter (mm) is a unit of length in the metric system, also known as the International System of Units (SI). One millimeter is one-thousandth of a meter.
Millimeters are often used to measure small objects or in technical specs. Lens sizes for cameras are usually given in millimeters.
What’s an inch?
An inch (in) is a unit of length in the imperial and U.S. customary systems of measurement. One inch is exactly 25.4 millimeters.
Inches are often used to describe the size of TV or computer screens. You may also see inches used in clothing measurements or in construction.
How to convert 39mm to inches
The key to converting millimeters to inches is knowing the conversion factor: 1 inch equals 25.4 millimeters. This number is important if you want an accurate conversion.
To convert millimeters to inches, you use this formula:
Inches = Millimeters / 25.4
So, to convert 39mm to inches:
39 mm / 25.4 mm/inch = 1.535 inches (approximately)
Therefore, 39 mm is about 1.535 inches.
How to convert millimeters to inches by hand
If you want to do the conversion yourself, here’s the process:
Using the conversion formula
To convert from millimeters to inches, use the formula: Inches = Millimeters / 25.4.
- First, identify the number of millimeters you want to convert. In this case, it’s 39 mm.
- Next, divide 39 by 25.4.
- The result is 1.535 inches (approximately).
Depending on what you’re measuring, precision may be important. If so, use the full decimal. If not, you can round to 1.54 or even 1.5 inches.
Understanding fractional inches
Sometimes it’s more useful to express the decimal portion of an inch as a fraction.
The decimal 0.535 inches is about 17/32 of an inch. So, 39 mm is just a hair over 1 and 1/2 inches. When precision isn’t paramount, you can use 1 and 1/2 inches as your measurement.
When might you need to convert 39mm to inches?
You may need to convert millimeters to inches in all sorts of situations. For instance, say you need to drill a 39mm hole, but your drill bit set is in inches. You’ll need to know the inch-equivalent to find the right bit.
Or, maybe you have an object that’s 39mm wide, and you need to know if it will fit in a space measured in inches. In both cases, you’ll need to convert 39mm to inches.
When you’re converting, think about how precise you need to be. In some cases, a rough estimate is fine. For more complex conversions, you can always use an online converter for a quick and accurate answer.
Conversion Charts and Tables
Another way to quickly find out what 39mm is in inches is by using a conversion chart or table. These charts give you the inch equivalent for millimeters, often showing both the decimal and fractional inch values.
If you regularly need to convert between millimeters and inches, these tables can be super handy. They’re easy to use and can save you time.
We can’t include a full conversion chart here, but you can find tons of them online with a quick search.
Frequently Asked Questions
Is 40 mm one inch?
Not quite. Since 1 inch equals 25.4 millimeters, 40 millimeters is a bit more than one and a half inches. To be precise, 40 mm equals approximately 1.5748 inches. So, while it’s close, it’s not exactly one inch.
What is 39 cm in inches?
Centimeters are bigger than millimeters, so 39 centimeters is quite a bit more than 39 millimeters! One inch is equal to 2.54 centimeters, so 39 cm is equal to 15.3543 inches.
What size is 35mm in inches?
Using our conversion again (1 inch = 25.4 mm), 35 millimeters is equal to approximately 1.37795 inches. So, just over one and a third inches. This is a common size, you may see this measurement when shopping for things like camera lenses.
Is 38mm 1 inch?
No, 38mm is not equal to one inch. Since 25.4 millimeters equals one inch, 38 millimeters is closer to one and a half inches. To be exact, 38 millimeters is about 1.496 inches.
Key Takeaways
Millimeters (mm) and inches (in) are two common units of measurement. To convert from millimeters to inches, you can use the formula: inches = millimeters / 25.4. That means 39 mm is about 1.535 inches.
Knowing how to convert between metric and imperial units like these is important in engineering, manufacturing, construction, and many other fields.
Now that you’ve learned how to convert from millimeters to inches, you can confidently make these conversions whenever you need to.