How to Convert Millimeters to Thou (Mils) Millimeters are commonly used in metric engineering. To express them in thou (mils), divide by 0.0254. The Mathematical Formula To convert millimeters to thou, divide the millimeter value by 0.0254: Thou = Millimeters ÷ 0.0254 Millimeters to Thou Table Millimeters (mm) Thou (mil) 1 mm39.37 thou 0.5 mm19.685 thou 2.54 mm100 thou 25.4 mm1000 thou
