Between the 1930s and 1960s, the field of demography developed in close association with eugenics in the International Union for the Scientific Study of Population Problems, the United Nations Population Division, and the Population Council. Through a genealogy of transatlantic demographic theory and measurement practices, the paper illuminates the eugenic logic inscribed in demographic calculations of ‘natural’ fertility and prescriptions for biomedical interventions to control national population trends in the Global South. The paper argues that demography reaffirmed eugenic gender politics expressed in the singular concepts of the individual/the national interest and the human body/the body politic. It shows that demographic narratives/figures presume an (implicitly masculine) modern individual actor whose reproductive decisions encode market logic into national population dynamics. The other sex, women are merely the biological mediums through whom those reproductive decisions pass, and, therefore female bodily events (e.g. age of menarche, age of first birth, etc) become the objects of demographic measurement practices. Moreover, demographic narratives and population figures simultaneously refurbish eugenic tools for ranking men and nations on the scales of modernity. That is, demographic figures array nations on a progressive scale of improvement (triumph) over natural fertility and mortality trends, thereby making purposive regulation of national population trends a requisite feature of economic modernization. Such measurement practices obscure the gendered social relations of reproduction with naturalized scripts. Thus, pregnancy risk is calibrated to ovulation rather than intercourse, foreclosing scrutiny of the heterosexual practices, or any gender-based conflicts within them. Likewise, the demographic scales of modernity reinvigorate imperial eugenic regulatory scripts in their contrast of restrained modern (European) men, reflected in lower fertility rates, with unrestrained brutes of lesser nations, whose high fertility rates reflect disregard for women and economic backwardness.