The known amplitude-sensitive eddy-current method for measuring the thickness of a non-conductive coatings on a conductive non-magnetic base metals does not satisfy the accuracy requirements. A primary consideration is the significant influence of a change in the specific elec-trical conductivity of the base metals on results of measurements. In this study we develop a tech-nique for measuring the thickness of a non-conductive coatings on a non-magnetic conductive base metals by using the eddy-current amplitude-phase method, and implement algorithms to process obtained information. Our method takes into account the influence of the specific electrical con-ductivity of the base metals by forming a two-dimensional graduation characteristic of the thick-ness gauge by using several base metals with different electrical conductivity. The algorithm for point-in-polygon determination is applied, which allows us to measure the thickness of the coat-ings and the specific electrical conductivity of the base metals as independent values. The equip-ment necessary to construct the two-dimensional graduation characteristic and the algorithm for calculation of the thickness are described in detail.