A standardized protocol for identifying the pore size of membranes is crucial for ensuring consistency and facilitating comparisons across different studies. Here, we introduce a comprehensive methodology that outlines the steps and necessary precautions for determining the pore size distribution of porous membranes. Our approach relies on a pre-developed probability density function (PDF) model, utilizing rejection values of electroneutral solutes by the membrane. For a comprehensive understanding of alternative methods of pore size estimation and their comparative analysis with the approach presented here (PDF model), please refer to our earlier work, Sutariya and Karan [1]. The data presented here are taken from our work, Puhan et al. [2], which can be referred to for the execution of this protocol.