Diffusion coefficients of adsorbed gases on porous solids can be obtained by analyzing solely experimental data derived from impedance spectra. In order to calculate it, a new approach has been developed in this study by fitting imaginary data with the imaginary part of the Warburg elements in case of the finite-length diffusion. Accordingly, two important diffusion parameters including the diffusion time constant and diffusion length are determined. This method along with the effective permittivity model is going to show significant parameters of diffusion process, e.g. Debye length, diffusion length, diffusion resistance, relaxation time, diffusion time constant, and diffusion coefficients. These values are also evaluated by making comparison of literature and the author's own experimental data. (c) The Author(s) 2018. Published by ECS.