In response to an increasing demand for rigorous monitoring of states in meeting their human rights obligations, a growing literature has emerged on measuring human rights fulfillment. Data are increasingly used in human rights assessment and advocacy but with an ad hoc approach, with three common limitations: frequent use of subjective indicators; focus on the right bearer enjoyment of right without taking account of duty bearer conduct; and event or country specific analysis that does not allow comparisons over time or space. This paper explores a methodology for measuring economic and social rights fulfillment that is reliable and authoritative. It proposes a composite index that: uses available survey-based objective, rather than subjective, data; focuses on state obligations rather than solely on individual enjoyment of rights; and captures progressive realization of human rights subject to maximum available resources. Two calculation methods are proposed: the ratio approach and the achievement possibilities frontier approach. The paper identifies key conceptual and data constraints. Recognizing the complex methodological challenges, the aim of this paper is not to resolve all the difficulties, but rather to contribute to the process of building rigorous approaches to human rights measurement. The proposed index provides important new information compared with other measures of economic and social rights fulfillment; although it still does not fully capture some desired features such as the right to nondiscrimination and equality, and the right to social security. The paper also outlines an agenda for longer term research and data collection that would make more complete measurement possible.