Film thickness is usually measured in mm or µm (micrometer, 1000 µm = 1 mm) or mil (1/1000 inch = 25.4 µm). Rough film surfaces can actually be deformed by measurement tools, which can press down surface peaks. Thickness measurement is not standardized. The result depends on the parameters of the measurement tools, including pressure force, and shape and diameter of the measurement heads.
Frequently used parameters are: flat/flat, AE 10 mm, force 1.2 N (Mitutoyo 543-250B) Micrometer screw: flat/flat, AE 6.25 mm, 5-10 N (Mitutoyo 293-521)