A realistic approach for determining the pore size distribution of nanofiltration membranes

•Various methods of determining the membrane pore size are discussed.•The probability density function (PDF) is the most suitable method which determines the mean pore size along with the pore size distribution (PSD).•A few important points to be contemplated for standardization of the PDF method have been deliberated.•The standardized PDF method will enable the comparison of results from different studies.