This paper addresses the issue of classification devices and their role in the shaping of markets. We depart from the notion that markets are shaped by multiple calculative agencies and examine how particular forms of calculation are made viable and sustainable. Classification devices, we argue, are the infrastructure that makes calculation possible and sustain particular forms of economic ordering. We illustrate these notions with an empirical, longitudinal study of a fuel retail company and its initiative to re-classify its network of petrol stations across Europe. Our study focuses on the extensive and protracted negotiations over what constitutes appropriate or relevant categories and the multiple perspectives that can be employed to define petrol station types. We illustrate how a store typology plays an important role in making assemblages of ideas (e.g. consumer-on-the-go), objects (e.g. store planograms), and managerial roles (e.g. category managers) coalesce around particular constellations of practices and impact upon the outline of markets.