The P.I.G paint inspection gauge 455 is used wherever conventional electromagnetic measurement methods fail (e.g. for coatings on wood, concrete, plastic and other non-metallic substrates). The P.I.G. 455 is based on the standardized wedge cut method: The coating is scratched through at a predetermined angle into the substrate. The coating thickness (s) is calculated from the cutting edge projection (b) (as determined by a measuring microscope) and the cutting angle (α). Similarly, the individual paint/coating thicknesses can also be determined for multi-layer systems.