Abstract A method for internal calibration of ESCA (XPS ) spectra is described that permits the use of a simple relation between binding energy ( E b) and atomic charge ( q) : E b = kq + E b0. This relation has been shown to hold for a large number of elements. So far the relation for carbon has, however, not been very well established. A method is now described that allows the use of carbon charges determined from E b, vs. q correlations for other elements and has also made it possible to establish a linear relation for carbon. The method does not use carbon charges determined directly from quantum chemical calculations. As an essential part of this procedure we investigated empirically the possible relation between the difference between the gas phase calibration standard and that for the same element in the solid state, “a”, and the molar polarizability of the substance, P. It was found that “a” decreases with increasing polarizability, tentatively as a=4.15+8.30 P − 1 3 . Therefore, knowledge of the polarizability of carbon-containing molecules from the literature made it possible to determine “a” and then the charge of all other atoms in the molecule. In this way a set of E b and qc date was obtained. These data were complemented by another set using theoretical q c snd solid state E b of phenyl compounds previously made. The results of the investigation show a linear relation between E b(Cls) and q c valid for the solid state: E b,(Cl s) = 4.68 q c + 286.2 eV with a correlation coefficient of 0.945. This brings the previously obtained k value for carbon, which seemed anomalously high, down to a value of similar magnitude as for other light elements.