This chapter examines the complicated and frequently disputed connection between justice and well-being in the context of empirical cooperation. It espouses an epistemologically sound, ethically reflective approach to metrics of justice in refutation of the false dichotomy between normativity and data. The chapter shows how the results of empirical traditions in various fields, including economics, psychology, sociology, and development studies, underpinned by a critical approach to these traditions and their assumptions, can be used to help illustrate patterns of structural inequality, confirm personal experiences, and guide public discourse about justice-related indicators. It challenges the main methodological issues, including cultural translation, reification of measures, and the boundaries of quantification, and promotes a mixed methods approach with narrative, participatory, and ethnographic epistemology. This chapter also provides case studies on the operationalization of justice in the global policy context, such as the Capability Approach, redistributive programs, and empowerment initiatives. It ends by reformulating empirical inquiry not as a special form of inquiry about the descriptive facts that empirical studies seek to determine but rather as a variant of moral reflection and public reasoning, which prefigures the sectoral applications of justice measures in the following chapter.