There is increasing interest in urban food production for reasons of food security, environmental sustainability, social and health benefits. In developed nations urban food growing is largely informal and localised, in gardens, allotments and public spaces, but we know little about the magnitude of this production. Here we couple own-grown crop yield data with garden and allotment areal surveys and urban fruit tree occurrence to provide one of the first estimates for current and potential food production in a UK urban setting. Current production is estimated to be sufficient to supply the urban population with fruit and vegetables for about 30 days per year, while the most optimistic model results suggest that existing land cultivated for food could supply over half of the annual demand. Our findings provide a baseline for current production whilst highlighting the potential for change under the scaling up of cultivation on existing land.Food security and agricultural sustainability are global issues of rising concern 1 . This is driven by the challenge of feeding a growing population from a finite and diminishing global soil resource 2,3 , and by the spatial disconnection between agricultural production and the urban systems in which an ever increasing proportion of that population live 4,5 . We expect changes at relatively local scales to be important in meeting these challenges 6 . The potential of own-grown urban food production (i.e. recreational or non-commercial gardening) as a local solution to a global problem has attracted increasing interest in recent years 5,7-15 , driven by a multitude of ecological, sustainability, social, recreational, therapeutic, mental and physical health, and well-being benefits to local areas and residents 3,11,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] .Whilst urban agriculture and own-growing have attracted considerable interest and advocacy, systematic evaluation of their proposed benefits remains limited 13,[36][37][38][39] . Quantitative estimates of actual and potential urban food production are key to such evaluations, but are rare 34,[40][41][42] . This stems from both the relatively recent interest in the subject and the specific challenges associated with obtaining such estimates. Nonetheless if the role of city-wide urban food production is to be assessed, and its relationships to urban form and to other ecosystem services are to be understood 35,43 , such data are crucial.Estimating urban food production is challenging, as it is spread over many highly fragmented and usually small growing spaces, managed by many different users growing a wide variety of often finely intermingled crops. Further, much of the consumption is direct, not passing through any transaction which would generate systematic records 40 . For example, in the United Kingdom, urban food production predominantly occurs in either private residential gardens or communally administered allotment sites. Allotments are generally managed by local authorities or o...