Parametric study of the thin shell solution of internally pressurized spherical vessel–cylindrical nozzle juncture is used to develop simplified closed-form formulas of stress concentration factor (SCF) as functions of the key vessel–nozzle geometric parameters known to influence the solution. The SCF values are not based on the vessel stresses alone; nozzle stresses are also analyzed and the corresponding SCF determined. Therefore, for a given vessel–nozzle juncture, the designer will be left with adequate information upon which to decide the controlling SCF. Predictions by the proposed equations are validated using finite element method (FEM). Consequently, design charts are presented based on both the vessel's and nozzle's SCF as predicted by the proposed expressions.