This research uses GoGebra aided Realistic Mathematics Education activities to develop concept understanding. This research was design research and impelemented in class 8th at one of schools in Indonesia. The data collection techniques and analyzed data through video recording, test, interview, and documentation. The results showed that GeoGebra aided Realistic Mathematics Education can develop student’s concept understanding about determine circumference and wide of circle.

Keywords : Circle, Understanding Concepts, GeoGebra, RME.