Increased use of scales in data-driven consumer digital platforms and the management of organisations has led to greater interest in understanding social and psychological measurement expertise and techniques as historically constituted ‘technologies of power’ in the making of what Stark has labelled the ‘scalable subject’. Taking a genealogical approach, and drawing on published and archival data, this article focuses on self-rated health, a scale widely used in population censuses, national health surveys, patient-reported outcome measurement tools, and a variety of digital (...) apps. The article suggests that the first methodological articulation of self-rated health by the investigators of the Cornell Study of Occupational Retirement (1951–58) provides a window into the key epistemic, institutional, and cultural uncertainties about psychological and social measurement, processes of adjustment to ‘old age’, and the capacity of individuals to value their own health. I propose that these uncertainties have become incorporated into extant and operational measurements of health. (shrink)