This chapter reviews existing studies of biodiversity offsetting (BDO), focusing on the development and application of metrics that create seemingly comparable measures of biodiversity to demonstrate measurable gains – or ‘yields’ in biodiversity unit value. It presents an example of how a conservation ‘valuation’ approach is mobilised in practice. From 2014 onwards, Department for Environment, Food and Rural Affairs (DEFRA) quietly let the spotlight fade from the BDO approach as a legislated policy requirement for the management of development impacts in England. Elements of both points suggest that the pressure of creating value for money in compensation strategies for conservation may be pushing BDO in directions that favour the growth of market values and exchanges for offset units, but that may work against the robust generation of conservation value. The biodiversity impact assessment spreadsheet operationalises the DEFRA BDO metric to arrive at biodiversity unit scores for each bounded habitat type on the development site.