A measurement of 7 mm (millimeters) is about 0.27559 inches. This value is equal to 9/32 of an inch. If you have a ruler on hand, 7 mm is close to (but not exactly) 1/4 of an inch. To understand how to convert millimeters to inches, it’s useful to know how to do a few basic conversions.

**How Many Inches Are in a Millimeter?**

There is 0.03937 of an inch in 1 millimeter. This amount reads 3/64 when converted to fraction form. Once you know how many inches are in a single millimeter, you can use this info to determine the number of inches in any amount of millimeters. You just need to multiply 0.03937 by the number of millimeters you have. For example, the 0.27559 inches that’s equal to 7 millimeters is the same as multiplying 7 by 0.03937.

**H****ow Many Millimeters Are in an Inch?**

You may want to do conversions that assist you with converting millimeters to inches. To do these calculations, you must know that 1 inch contains 25.4 millimeters. If you need to convert inches to millimeters, you will multiply the number of inches by 25.4. Assume that you want to convert 7 inches to millimeters; when you multiply 7 by 25.4, the result is 177.8 millimeters.

**A**** Guide to Checking Your Conversions**

When converting from one unit to another, you may have concerns about the accuracy of your results. Fortunately, there is an easy way to check the results of your calculations.

Take the previous example where you converted 7 millimeters into inches, which gave a result of 0.27559. To check your work, divide the end result by 7 (the number you were converting). When you divide 0.27559 by 7, the result is 0.03937, which is the number of inches in 1 millimeter. This is the number that you used for your initial calculations. When checking your work, dividing the final answer by the amount that you were converting should give you the other value that you used for your conversions.

**T****ips for Deciding How Many Digits to Carry After the Decimal Point**

When you’re going from one unit of measurement to another, you’ll notice that some of the conversions are “messy.” They result in numbers with a lot of digits after the decimal point. To make your calculations a little simpler, you can round your figures to a certain figure after the decimal point.

Which spot after the decimal point you round to depends on the desired accuracy of your numbers and how clean you want the numbers to appear. If you’re going to use the numbers in a presentation or project, round your numbers to the tenths or hundredths place. This will ensure your numbers are easy for your audience to read. For example, if your figures reads 4.5678, rounding to the tenths place will yield 4.6. Rounding to the hundredths place gives you 4.57.

If accuracy is your goal, round to the thousandths or ten-thousandths spot. The more digits you keep after the decimal point, the more accurate your calculations. Rounding 4.5678 to the thousandths place yields 4.568.

Make sure you remain consistent. Pick a spot after the decimal point and stick with it.

**T****ips for Deciding Whether to Use or Inches or Millimeters **

Millimeters and inches are both used to measure items with short lengths. However, millimeters offer a higher level of precision. It’s easier to read a metric ruler than an imperial ruler for these excessively small items. If you’re using measurements in a lab setting, it’s usually customary to use a metric measurement like the millimeter.

Inches are ideal if you’re dealing with an audience that doesn’t know the metric system or for items that measure at least 1 inch in length.