Converting measurements from inches to millimeters is a fairly easy math job. Here's how to do it.
Step
Method 1 of 4: Basic Equations
Step 1. Understand the relationship between inches and millimeters
Internationally, one inch is recognized as equivalent to 25.4 millimeters.
- Written as an equation, this relationship is written as: 1 in = 25.4 mm
- This official and standardized measurement has been regulated in international rules since 1959.
- Both inches and millimeters are units of measurement. The inch belongs to the British system of measurement, while the millimeter belongs to the metric system of measurement.
- If the inch is used in the United States, United Kingdom, and Canada, you will often have to convert these units of measurement to the metric system (such as millimeters) for scientific purposes.
- In contrast, there are 0.0393700787402 inches in one millimeter.
Step 2. Write down the inch measurement
To change a measurement in inches, you'll need to start by writing down your original measurement.
- This measurement will then be converted to millimeters by comparing it to the relationship between inches and millimeters.
- Example: 7 inches
Step 3. Multiply this measurement by 25, 4
You will need to multiply that inch measurement by the ratio of millimeters per inch, or 25.4 mm / 1 in.
- The inch value in this comparison should be put in the denominator because it will omit the inch value in your original measurement. Once all the inches are removed, the millimeter will be the only unit of measurement remaining.
- Example: 7 in * (25.4 mm / 1 in) = 177. 8 mm * (in/in) = 177. 8 mm
Step 4. Write down the final answer
If you do the problem correctly, the answer you get will be your final answer in millimeters.
Example: 177, 8 mm
Method 2 of 4: The Short Way
Step 1. Check a ruler
The ruler is 12 inches or 1 foot long. Many rulers write inches on one side but also write centimeters and millimeters on the other. If your initial measurement was 12 inches or less, you can use one of these rulers to measure the same distance in millimeters.
Note that the millimeter mark on the ruler is the small line between the larger centimeter measurements. There should be 10 mm every 1 cm
Step 2. Use the website to automatically change the measurements
If you need to quickly find the millimeter measurement equivalent to inch measurement, you can do so using an automated conversion website.
- Go to the website and look for the conversion box.
- Type a number into each box and select the unit you want to convert, if needed.
- Press the Calculate button or another button to show the answer.
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Websites that will help you do this calculation include:
- MetricConversions. Org (https://www.metric-conversions.org/length/inches-to-millimeters.htm)
- CheckYourMath. Com (https://www.checkyourmath.com/convert/length/inches_mm.php)
- In addition, you can type a question (eg 7 in = mm) directly into many search engines, including Google and Bing, and the search engine will modify the problem and return the answer to you on the results page.
Step 3. Take a look at the frequently used conversion tables
For smaller inch measurements, you can look up the measurements in a conversion table, such as the table below. Find the inch measurement and look next to it to see the millimeter measurement that is equivalent to the inch.
- 1/44 in = 0.3969 mm
- 1/32 in = 0.7938 mm
- 1/16 in = 1.5875 mm
- 1/8 in = 3, 1750 mm
- 1/4 in = 6.3500 mm
- 1/2 in = 12, 7000 mm
- 3/4 in = 19, 0500 mm
- 7/8 in = 22, 2250 mm
- 15/16 in = 23, 8125 mm
- 31/32 in = 24, 6062 mm
- 63/64 in = 25.0031 mm
- 1 in = 25, 4001 mm
- 1 1/8 in = 28.5750 mm
- 1 1/4 in = 31, 7500 mm
- 1 3/8 in = 34, 9250 mm
- 1 1/2 in = 38, 1000 mm
- 1 5/8 in = 41, 2750 mm
- 1 3/4 in = 44, 4500 mm
- 2 in = 50, 8000 mm
- 2 1/4 in = 57, 1500 mm
- 2 1/2 in = 63.5000 mm
- 2 3/4 in = 69, 8500 mm
- 3 in = 76, 2000 mm
- 3 1/4 in = 82.5500 mm
- 3 1/2 in = 88, 9000 mm
- 3 3/4 in = 95, 2500 mm
- 4 in = 101, 6000 mm
- 4 1/2 in = 114, 3000 mm
- 5 = 127,000 mm
- 5 1/2 in = 139, 7000 mm
- 6 in = 152, 4000 mm
- 8 in = 203, 2000 mm
- 10 in = 254, 0000 mm
Method 3 of 4: Related Work
Step 1. Convert inches to centimeters
There is 2.54 cm in 1 inch, so to convert inches to centimeters, you need to multiply the original inch measurement by 2.54 centimeters.
- Example: 7 in * (2.54 cm / 1 in) = 17.78 cm
- Note that the centimeter measurement has one decimal place larger than the millimeter measurement. If you have a millimeter measurement, you can also find a centimeter measurement by moving the decimal one place to the left.
Step 2. Convert inches to meters
There are 0.0254 m in 1 inch, so to convert inches to meters, you need to multiply the original inch measurement by 0.0254 m.
- Example: 7 in * (0.0254 m / 1 in) = 0.1778 m
- Note that meter measurements have three decimal places greater than millimeter measurements. If you have a millimeter measurement, you can also find the meter measurement by shifting the decimal three places to the left.
Step 3. Convert millimeters to inches
If you want to calculate the inch measurement when you have a millimeter measurement, you can do this by multiplying the millimeter measurement by 0.0393700787 inch or dividing the millimeter measurement by 25.4 millimeters.
- Example: 177.8 mm * (0.0393700787 in/1 mm) = 7 in
- Example: 177.8 mm * (1 in/25.4 mm) = 7 in
Method 4 of 4: Examples
Step 1. Answer the question: How many millimeters are in 4.78 inches?
To find the answer, you have to multiply 4.78 inches by 25.4 millimeters.
4.78 in * (25.4 mm / 1 in) = 121, 412 mm
Step 2. Convert 117 inches to millimeters
Make the conversion by multiplying 117 inches by 25.4 millimeters.
177 in * (25.4 mm / 1 in) = 4495, 8 mm
Step 3. Determine how many millimeters are in 93.6 inches
This answer can be found by multiplying 93.6 inches by 25.4 millimeters.
93.6 in * (25.4 mm / 1 in) = 2377.44 mm
Step 4. Know how to convert 15, 101 inches to millimeters
Find the answer by multiplying 15, 101 and 25.4 millimeters.
