The Math.com conversion table states that one inch is the equivalent of .0254 meters which is 25.4 millimeters. It is possible to convert any length in inches into millimeters by multiplying the number of inches by 25.4.
Since inches are a form of standard measure and millimeters are used in the metric system, conversion is not as straightforward as converting millimeters to centimeters, for example. Further calculation allows for conversion of inches into meters by dividing the resulting number of millimeters by 100 or converting millimeters into feet by first dividing the number of millimeters by 25.4, then multiplying it by 12.
There are just over 25 millimeters in every inch. That means, in one foot there are almost 300 millimeters. And in every yard, 900 millimeters.
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1 inch = 25.4 millimeter.
http://wiki.answers.com/Q/How_many_inches_equal_mi...

1 inch equals 25.4000mm. Thanks for using ChaCha!
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In every inch, there are 25.4 millimeters. Count carefully! By the way, there are 10mm in a cm!
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