Previous research has shown that parental involvement at home seems to be socio-economically stratified. To study this stratification, recent research has drawn a distinction between early and late parental literacy activities at home. Early parental literacy activities at home happen before primary school, whereas late parental literacy activities at home occur during the time at primary school. In this article, we focus on the relationships between early and late home-based parental literacy involvement and reading literacy in Western Europe. The goal is to advance our understanding of these relationships by formulating and testing equations that explain the level of parental literacy involvement and reading literacy within a specific range of uncertainty. So far, no efforts have been made in the literature on parental literacy involvement and reading literacy, to formulate, create and test such equations.