Measuring and being measured are some of the fundamental aspects of our worlds. Without them, we cannot live in our environments or function as social beings. But how we measure, and are measured, and to what ends and purposes, matters a great deal. Measurement does not just record; it shapes, changes, and constitutes things. It is not merely descriptive. It is creative. This introduction to the special issue explores how these themes of measurement are played out in diverse settings, including counting fish stocks, migration, social resilience, local measures of sustainability, oil exploitation, forest conservation, calculating ecosystem services, and measuring heat. Collectively, they provide a better understanding of how crucial measurements are formulated, and how they are and can be contested.