The quasi-Gaussian entropy (QGE) theory was used to formulate a statistical mechanical model describing the thermodynamics of the folding/unfolding process of single-domain proteins. The model was parametrized using experimental data obtained from differential scanning calorimetry (DSC) of a set of proteins. The results showed that the model is able to reproduce the experimental behavior in the usual temperature range, for all the analyzed proteins. Furthermore, a remarkable similarity of some parameters of the model, when normalized per residue and corresponding to well-defined physical properties, was found. Interestingly, at low temperature, the model provides cold denaturation features for all the proteins. Finally, a general description of the folding/ unfolding process and stability, based on the physical view provided by the model, is discussed.