Determination of the effective capacitance of passive films remains a difficult challenge and mostly relies on the assumption the contribution of the double layer can be neglected. Such an approximation is easy to verify a posteriori when data analysis is performed assuming that each of the contributions is a capacitance and that the order of magnitudes for the double layer capacitance is between 10 to 50 µF cm-2 for a wide range of electrolyte concentrations and over a large potential window. However, both the electrochemical impedance of passive film and double layer relaxation usually exhibit a non-ideal behavior, thus resulting in the use of constant-phase elements (CPE) to account for the distribution of dielectric properties of the interface as well as experimental factors (position of the reference electrode, adsorption of impurities…). We have previously shown that the analysis of impedance data by the representation of complex capacitances makes it possible to determine certain interface properties, especially thanks to the exploitation of the high-frequency domain 1-3. In this work, a special attention is paid to the graphical analysis of the experimental data in the different frequency ranges, including the low-frequency domain, in order to determine the values of the capacitances without resorting to fitting procedures involving complex functions. It will be shown that such an approach allows determination of the thickness of a thin layer at the interface, independently of the use of a CPE to describe the distribution of time constants. (1)Benoit, M.; Bataillon, C.; Gwinner, B.; Miserque, F.; Orazem, M. E.; Sanchez-Sanchez, C. M.; Tribollet, B.; Vivier, V. Comparison of different methods for measuring the passive film thickness on metals. Electrochim. Acta 2016, 201, 340. (2)Chakri, S.; Frateur, I.; Orazem, M. E.; Sutter, E. M. M.; Tran, T. T. M.; Tribollet, B.; Vivier, V. Improved EIS Analysis of the Electrochemical Behaviour of Carbon Steel in Alkaline Solution. Electrochim. Acta 2017, 246, 924. (3)Chakri, S.; Patel, A. N.; Frateur, I.; Kanoufi, F.; Sutter, E. M. M.; Tran, T. T. M.; Tribollet, B.; Vivier, V. Imaging of a Thin Oxide Film Formation from the Combination of Surface Reflectivity and Electrochemical Methods. Anal. Chem. 2017, 89 (10), 5303.