7 millimetres (mm) is about 0.27559 inches (inches). 9/32 of an inch is the same as this value. If you have a ruler, 7 mm is almost 1/4 of an inch, but not quite. To understand how to convert millimetres to inches, it helps to know how to do a few basic conversions.

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## How Many Inches Are There in a Millimeter?

One millimetre is equal to 0.03937 of an inch. When this amount is turned into a fraction, it is written as 3/64. Once you know how many inches are in one millimetre, you can use this information to figure out how many inches are in any other number of millimetres. All you have to do is multiply 0.03937 by how many millimetres you have. For example, multiplying 7 by 0.03937 gives you 0.27559 inches, which is equal to 7 millimetres.

## How Many Millimeters Are There in an Inch?

You might want to do conversions to help you go from millimetres to inches. For this, you need to know that 1 inch is equal to 25.4 millimetres. If you need to convert inches to millimetres, multiply the number of inches by 25.4. If you want to know how many millimetres 7 inches is, you multiply 7 by 25.4, which gives you 177.8 millimetres.

## How to Check if Your Conversions Work

You might worry about how accurate your results are when you change from one unit to another. Luckily, there is a simple way to make sure that your calculations are correct.

In the last example, you changed 7 mm to inches and got 0.27559. To make sure your work is correct, divide the result by 7. (the number you were converting). When you divide 0.27559 by 7, you get 0.03937, which is how many inches there are in 1 millimetre. This is the number you used when you first did your math. When checking your work, divide the final answer by the amount you were converting to get the other value you used in your conversions.

## How to Figure Out How Many Digits to Keep After the Decimal Point

When going from one unit of measurement to another, you’ll notice that some of the conversions are “messy.” They lead to numbers with a lot of digits after the decimal point. You can round your numbers to a certain number after the decimal point to make your calculations easier.

Which number you round to after the decimal point depends on how exact you want your numbers to be and how clean you want them to look. If you want to use numbers in a project or presentation, round them to the tenths or hundredths place. This will make sure that your numbers are clear and easy to read. If your numbers add up to 4.5678, for example, rounding to the tenths place will give you 4.6. 4.57 is the answer when you round to the hundredths place.

If you want to be exact, round up or down to the thousandths or ten-thousandths place. The better your calculations are, the more numbers you keep after the decimal point. If you take 4.5678 and round it to the thousandths place, you get 4.568.

Make sure you remain consistent. Choose a place after the decimal point and stay there.

## Advice on Choosing Between Inches and Millimeters

Both millimetres and inches are used to measure things that aren’t very long. But millimetres are better because they are more precise. For these very small things, it is easier to read a metric ruler than an imperial ruler. In a lab, it is common to use metric measurements like the millimetre when taking measurements.

If your audience doesn’t know about the metric system or if your item is at least 1 inch long, you should use inches.

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