The apparel retail industry is on the one hand facing challenges from increasing competition, consolidations, and thus increasing pressure to reduce costs. On the other hand, customers are getting more demanding, resulting in shorter fashion cycles, and demands for new customer experience. RFID technology is supposed to raise efficiency and to enable innovative customer service offerings. Besides cost savings, benefits are expected to arise from newly designed RFID applications and customer insights from analyses of shop floor data. Recently, apparel retailers started to investigate this technology, resulting in several trials and pilots world-wide. However, the business case of RFID in the apparel retail industry is not clear. Based on the findings of a real-world deployment, our contribution presents a cost-benefit calculator that is specifically designed to meet the requirements of apparel retail industry RFID implementations.