Precise knowledge of the local sample thickness is often required for quantitative scanning (transmission) electron microscopy (STEM). The local sample thickness can be determined by the comparison of measured intensities from high-angle annular dark-field (HAADF)-STEM at low energies (<30 keV) with Monte-Carlo simulations. However, a suitable choice of the scattering cross-section (CS) used in the simulations is necessary to gain reliable thickness results. In this work, simulations using different CS, including the Screened Rutherford CS and different Mott CSs, were performed. The results were then compared with measurements on samples with known thickness and composition, for which an SEM equipped with a STEM detector was used. In most cases, the Screened Rutherford CS describes the experiment better than other CSs.