A general calculation model is presented to determine the Linke turbidity factor, starting from the experimental datum of global daily solar radiation on the horizontal plane. The model was validated using experimental data for the turbidity factor obtained at Arcavacata di Rende (Cosenza) and at Casaccia (Rome). Moreover, polynomial relations are presented for quick calculation of this parameter on different days of the year for those localities for which the European Solar Radiation Atlas supplies the maximum solar radiation values on clear days.