Contemporary decisions about the management of populations, public services, security, and the environment are increasingly made through knowledge gleaned from 'big data' and its attendant infrastructures and algorithms. Though often described as 'raw,' this data is produced by techniques of measurement that are imbued with judgments and values that dictate what is counted and what is not, what is considered the best unit of measurement, and how different things are grouped together and "made" into a measureable entity. In this paper, we analyze these politics of measurement and how they relate to action through two case studies involving high stake public health measurements where experts intentionally leverage measurement to change definitions of harm and health. That is, they use measurement for activism. The case studies offer a framework for thinking about of how the politics of measurement are present in user interfaces. It is usually assumed that the human element has been scrubbed from the database and that significant political and subjective interventions come from the analysis or use of data after the fact. Instead, we argue that human-computer interactions start before the data reaches the computer because various measurement interfaces are the invisible premise of data and databases, and these measurements are political.