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How to Convert Millimeters to Inches

Converting millimeters (mm) to inches (in.)

To convert mm to in, multiply the number in mm by 0.039. This works for most applications.

If you need a more more precise conversion factor, then multiply by 0.0393700787.

Below are some additional resources to help with all of your metric to standard conversion needs.

Instructions

Use Google

Did you know that Google will do conversion calculations for you? For example, if you have a measurement of 51.2 mm and want to know what that corresponds to in inches, try going to Google and typing "51.2 mm to inches" into the search box.

The result you get will be a value of 2.01574803 inches, which is correct, but needs to be rounded to three significant digits because the original measurement only had three significant digits.

Use this printable conversion table

This table will allow you to quickly look up a number in mm and find its equivalent in inches, or vice versa, with the hassle of typing numbers into a calculator or doing a computation by hand. You can print out the table and post it in a classroom or workshop, or even carry it in your pocket for handy reference.

Significant digits

When converting between units, how do you decide when to round? This video helps explain the concept of significant digits.

Learn the basics of the metric system

Millimeters in an inch

photo by theilr

by Mark Sugrue

The international inch is defined exactly as 25.4 mmAt one time an 'inch' was a imprecise measurement. Often each town or region would have its own version, an this itself would change from time to ti...More>
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