This dissertation explores the development of quantitative dietary standards and their socio-economic consequences in modern Japan. By incorporating insights from the history of knowledge, I examine diverse and multilingual sources, both qualitative and quantitative, to elucidate how knowledge of dietary standards for the Japanese population were produced, circulated, and applied to people’s lives from the 1880s to the 1950s. This study reveals a close linkage between nutrition science and the food economy at both familial and national levels, which Japan scholars have often studied separately. I argue that the establishment of dietary standards paved the way for both micro- and macro-level applications of quantitative logic to the rationalization of individual nutrition and food economy, thereby reshaping food and nutrition policy making in modern Japan. The government compared agricultural production with the caloric needs of the entire population. During wartime and the occupation period, governing authorities and public health professionals developed nutritional and food policies to nourish a hungry population. People were encouraged to adhere to numerical standards of daily nutrient intake to optimize nutrition. The ideas and practices of calculated eating by standards, strenuously promoted by generations of nutrition professionals and embraced by many women responsible for household nutrition, transformed the nutritional awareness and dietary habits of the Japanese populace.