Abstract: In this exploratory study, we examined whether an online training program, STEM Fluency system, which was developed based on spaced retrieval and interleaved learning principles, helped students improve their mastery of an essential skill, metric conversion, through multiple mini sessions of spaced and interleaved online training. The study suggests that students significantly improved the accuracy in performing the three subskills of metric conversion. But the results were mixed when it comes to fluency. The implications of the study are discussed.