This study details cost accounting practices at a number of UScotton mills in the 1820s. While some extant literature suggeststhat these practices were akin to management accounting, wetake a different view. Drawing on an institutional lens and reverseengineering of cost calculations, we argue that these practiceswere indeed institutionalised, but that a merchant mindset oncosts and profits was engrained within them. Cost calculationswere based on the comparative quality of cloth, and costs werenot traced to a particular product. However, gradual change tookplace from about 1830 on, when cost calculations became morespecific to particular products, possibly as a consequence ofexternal economic forces.