In this paper, a parametric study of the Stress Concentration Factor (SCF) has been carried out in cylindrical pressure vessels with circular holes. A three-dimensional finite element analysis has been carried out performing a variation of dimensionless parameters (thickness ratio, size ratio and aspect ratio) exploring a wider range than other investigations. It is observed that the maximum value of the SCF increases as the hole size ratio and the aspect ratio increase, although the location of the maximum SCF is located from the internal area of the vessel to the external part depending on the geometric configuration, defining thus three differentiated zones. Additionally, in the final part of the document, a fit model is defined to determine the value of the maximum SCF for different continuous values of the defined dimensionless parameters. This model allows to quickly calculate or locate from a contour map the maximum value of SCF for a specific geometry of pressure vessel.