<p>This article proposes an approach to operationalizing Relative Deprivation (RD) in the context of the study of perceptions of economic inequality, offering a framework that shifts the focus from individual comparisons to societal-level perceptions of fairness. Grounded in Social Justice Theory and the Justice Evaluation Function, this study conceptualizes RD as the discrepancy between the economic inequality individuals perceive and the level they consider just. Unlike traditional RD measures, which centre on individuals’ relative standing within a social hierarchy, this approach captures how economic inequality itself can generate deprivation feelings. Using data from the International Social Survey Programme (ISSP), this article demonstrates the applicability of the proposed measure through an empirical analysis of Chile, a country marked by persistent economic disparities and recent large-scale social mobilizations against inequality. The findings reveal that deprivation feelings arise when perceived inequality exceeds an individual’s tolerable threshold of fairness, influencing attitudes toward economic justice. This operationalization advances RD theory by providing a continuous, quantitative measure applicable to cross-national studies and regression models. By bridging subjective perceptions regarding economic inequality and the development of deprivation feelings, this study contributes to a deeper understanding of how economic disparities shape social attitudes and potential collective action in contemporary societies.</p>