Windows is designed to use the metric system. It should be noted that:  


Many label manufacturer call their labels 4" x 6" , but they may in fact range in size from 100x150, 100x155, 100x160, etc.


For Windows, it is recommended to use millimeters as the measurement, so it will be necessary to convert from inches to mm.


To convert inches to millimeters on Google.

Please refer to this link: