We define a notion of ‘sensing capacity’ that characterizes the ability of a sensor network to successfully distinguish among a discrete set of targets. Sensing capacity is defined as the maximum ratio of target positions to sensors for which inference of targets within a certain distortion is achievable. We demonstrate a lower bound on this capacity. Unlike previous work on ‘sensor network capacity’, our notion of sensing capacity is defined by the sensing task itself, as opposed to external resource constraints such as power, communications, and processing.