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In this tutorial I have explained method of converting a drawing from inches to millimeter unit. The same method can be used to convert drawings from other units as well adn you can also use this method to convert AutoCAD drawings from imperial to metric and vice versa.

For more on -DWGUNITS command and drawing unit convertion tip visit http://www.thesourcecad.com/how-to-change-units-of-existing-drawing-in-autocad/