There is a large body of evidence for Roman use of weights and measures. In theory, they would have been able to measure a variety of quantities with great precision, given the variety of different-sized units at their disposal and an elaborate system of fractional subdivisions of those units. Moreover, those measurements could have been accurate with respect to a shared system because of publicly available exemplary standards, a theoretical connection between the definitions of the most important measurements, and the existence of state officials who could enforce the standards. As a result, Romans could, in principle, have conveyed very specific metrological information across a great deal of space and time. In practice, measurement was considerably less predictable and less precise. Actual measurement did not necessarily avail itself of the full resources of the theoretical system, and sometimes did not appeal to any general system. Moreover, overtly competing systems coexisted with the “official” ones at all times. Finally, it is not clear how coherent that official system was, nor were the actual systems of enforcement particularly robust. As a result, measurement was often imprecise and/or tightly localized (which probably generated weak expectations of being able to replicate measurement across different contexts).