This chapter draws on the example of the English planning system to examine the role of lawyers and planning law structures and judgements in shaping local decisions. It focuses, in particular, on the growing reliance on quantitative evidence in understanding urban problems, which have an impact on how cities are governed. The chapter shows how the calculative approach to viability illustrates the technocracy currently so prevalent in the English planning system. A reliance on numbers runs throughout the framework: in objective assessments of housing need, efficiency targets for local planning authorities, governance by statistics, and annual reports. It is viability assessments, however, that are so dominated by commercial calculative practices, particularly profit and loss.