Morphological productivity is difficult to define and describe. Nevertheless have several measures been proposed by scholars, in order to quantify this notion. This paper investigates ten common English prefixes with meanings related to degree or size. The aims of the study are (1) to review several measures of morphological productivity, (2) via a sample of corpus occurrences of ten prefixes, to calculate productivity figures using five different measures of productivity, and (3), perhaps most importantly, to discuss the differences and similarities of the five measures. The results suggest that while several of the measures are quite similar (e.g. type frequency and hapax legomena frequency), other measures are different (e.g. 'Productivity in the narrow sense'). While three of the measures could be said to provide information concerning past or 'factual' productivity, two of the measures seem instead to indicate an aspect of productivity that is referred to as 'potential' productivity.