In the 2012 PIAAC Survey of Adult Skills of 23 industrialised countries, the UK (England & NI) scored below average on adult numeracy. Several recommendations focus on the need for (some) individuals in the population to undergo training. Yet, even in "high-performing countries" like the Netherlands, many adults (1.5M) score at or below PIAAC Level 1 (sometimes designated as "functionally innumerate"). The question arises as to how all of these people manage in important domains of their lives. In this article we aim to consider the context of the exercise of numeracy by adults, drawing on earlier research in mathematics education. We examine a recent conception of an adult's "literate environment" (EU HLG on Literacy, 2012), and extend this to reflect on the idea of an adult's "numerate environment". We consider the range of practices that particular adults may engage in, and the demands that these may make on the adult, the affordances the practices may offer; the latter include the opportunities, and the supports and/or barriers produced within these practices, and in cultures more generally, that may foster or impede an adult's ongoing numerate development. We give examples of each of these aspects of adults' numerate practices, and consider implications for the teaching, learning and development of numeracy.