Converting Mils and Microns to Pounds and Kilograms. Converting Mils and Microns to Pounds and Kilograms. The conversion factor for mils ( 1 /1000th of an inch ) to microns ( 1/1000th of a millimeter) is 25.4. In other words, there are 25.4 microns in a mil. MILS THICKNESS: SQUARE INCHES PER POUND: