Population density in urban districts should bear specific determined values to produce interaction among community's individuals; contributing as well establishing sense of safety for individuals and achieve standardizations of social sustainability. Yet, the majority of the urban districts suffer either an increase or a decrease in density rate, affecting negatively the accomplishment of social sustainability criteria in those communities and consequently the ability to fulfill their citizens' needs. For the previous, this current paper drives at examining the relationship between population density and standardizations of social sustainability to reach a model specifies the appropriate population density in urban districts inside great Cairo, achieving in turn the social sustainability criteria. The research methodology depends upon two basic axes: the first axis is crystallized in considering the concept of social sustainability as well as the most significant standardizations of its implementation within urban population districts; focusing as well on population density as one of the standardizations of social sustainability. The second axis stands for examining the correlation between population density and standardizations of social sustainability through making a field study on several population districts inside Great Cairo, using statistical programmes in order to establishing a model for determining the appropriate density inside urban areas in Great Cairo in terms of accomplishment of social sustainability. The research concludes to defining the concept of social sustainability in urban districts in Great Cairo and the role of population density as one of the most important standardizations for achieving social sustainability. In addition, the research comes to designing this model through the field study that specifies the convenient values of density to be used to establish social sustainability within urban districts in Great Cairo.