The demand for cooling in buildings is persistently escalating and is estimated to reach a relevant share of overall building energy consumption in the coming years. This increase, accompanied by a corresponding rise in greenhouse gas emissions, is leading to an active investigation of novel passive cooling technologies, such as Daytime Radiative Coolers (DRCs). Regrettably, a universally accepted sizing methodology for DRCs is presently lacking, with only a limited number of simulation models having been developed thus far. This thesis work endeavors to formulate a comprehensive sizing procedure for DRCs, tailored to real-world conditions, with the ultimate aim of ensuring their effective operation during the cooling season.