AbstractA Monte Carlo code previously used in modelling x‐ray emission by incident electrons of several tens of kilo‐electronvolts has been extended up to 300 keV, which is typical of the present medium‐energy transmission electron microscopes. With the aid of a further numerical code, both the thickness and composition of thin self‐supporting films can be simultaneously determined. This code exploits the bootstrap statistical method, which provides a realistic error analysis of the final results from the precision of the experimental data. The potential of the two codes is illustrated through a simulated example of a single self‐supporting film. Such calculations can also be applied to two or more overlying films transparent to an elec