This article looks at the manner in which knowledge of slums in Delhi has been collected, assembled and circulated in two different moments of urban improvement to explore the relationship between calculation and governmentality. Based on an extended study of slum enumeration and the politics of slum demolitions in Delhi, I show that each of these two moments relied on an epistemologically different set of calculative practices – one statistical, the other aesthetic – to render the slum intelligible and secure rule. I specifically show how the statistically rigorous calculative practices of the first moment encountered various technical difficulties and political challenges in producing a governing intelligibility, thus leading to the unruliness of slum space. In response, a new set of governmental techniques operating through the dissemination of aesthetic norms and codes re-secured rule over slums. I describe this shift in governmental technique to demonstrate that the dissemination of aesthetic norms can be both more governmentally effective and practically implementable than the statistical deployment of governmental truths. This suggests the need to expand our understanding of the epistemology of government to include attention to a more diverse array of governmental technologies, some more aesthetic than strictly calculative.