X-ray photoelectron spectroscopy (XPS) is a widely used technique for analysing the chemical composition and thickness of thin film surfaces. In this study, the Simulation of Electron Spectra for Surface Analysis (SESSA) software is used to simulate XPS spectra for three different sample overlayers that are widely used in the semiconductor industry: gold (Au), silicon dioxide (SiO2), and hafnium oxide (HfO). The simulations are performed for a source energy range from 1000 eV to 10 keV, and a range of film thicknesses between 10 ̊A and 50 ̊A. In order to study the influence of elastic scattering effects on the prediction of surface thickness for low to high source energies, we compare two approaches: the straight line approximation (SLA) and the full elastic scattering (ES) model. We analyse the difference in the simulated peak area intensities in the two approaches used to predict film thickness as the source energy is varied. We find that the thickness can be predicted perfectly in the SLA, while significant deviations are observed in the ES model, even at high energies due to elastic scattering effects. In addition, by analysing the single scattering albedo i.e. the ratio between the inelastic mean free path and the transport mean free path, we can quantify the importance of elastic scattering effects at high energies for predicting the film thickness for the three materials. Furthermore, the SESSA software is used to investigate the influence of the detector solid angle on the prediction of the film thickness prediction for the two different approaches. We briefly demonstrate how variations in the detector’s solid angle in the range of 0◦to 60◦affect the accuracy and reliability of the thickness estimation, even when elastic scattering effects are neglected. Overall, this research contributes to the field of X-ray photoelectron spectroscopy by exploring the impact of elastic scattering effects at low and high source energies and highlights the importance of SESSA as a powerful tool for simulating and analysing XPS data. The results of this study improve our understanding of the underlying elastic scattering physics and provide practical guidelines for more reliable and accurate thin film characterisation using XPS.