This study was designed as a bottom-up approach to understand what kind of changeable functions people desire in transformable garments by analyzing a wardrobe database, participants' perceptions of garment varieties, and their values related to transformable garments. The wardrobe database (2009-2011) was analyzed using data quantification and descriptive analysis. Seven style-conscious professional working women, between the ages of 20 and 40 were interviewed focusing on their perceptions and values related to tops. Versatility was the most important reason for preferring specific changeable design functions. Participants had three expectations for transformable garments: functional, hedonic, and social. Functional expectations included ease of matching, ease of layering, comfort, usability, ease of care, and durability. Among functional expectations, usability, care, and durability, were requirements for frequent and long-term use of transformable garments. Participants wanted to have fun and be able to experiment with various styles in hedonic expectations. Social expectations were context aptness, and modesty. In this study, several models regarding transformable garments and criteria for evaluating transformable garment design were suggested. Among candidates for changeable design functions, the most preferred functions were transforming colors/patterns and sleeve lengths. Transformable garments have the potential to lead consumers' natural engagement with sustainable acts by satisfying their various needs and wants. In an effort to motivate consumers to care more about the sustainability of their clothing, many researchers have suggested educating consumers. However, transformable garments are expected to influence consumers to wear these pieces over longer periods of time and more frequently due to their ability to serve multiple needs. Even though consumers may lack knowledge or indicate little concern about sustainability, transformable garments have the potential to encourage them to engage in sustainable behavior without their awareness. Designers can support this behavior by encouraging consumers to naturally consider versatile, transformable fashion while still satisfying their needs and wants.