Spatial perception in virtual reality (VR) has been a hot research topic for years. Most of the studies on this topic have focused on visual perception and distance perception. Fewer have examined auditory perception and room size perception, although these aspects are important for improving VR experiences. Recently, a number of studies have shown that perception can be calibrated to information that is relevant to the successful completion of everyday tasks in VR (such as distance estimation and spatial perception). Also, some recent studies have examined calibration of auditory perception as a way to compensate for the classic distance compression problem in VR. In this paper, we present a calibration method for both visual and auditory room size perception. We conducted experiments to investigate how people perceive the size of a virtual room and how the accuracy of their size perception can be calibrated by manipulating perceptible auditory and visual information in VR. The results show that people were more accurate in perceiving room size by means of vision than in audition, but that they could still use audition to perceive room size. The results also show that during calibration, auditory room size perception exhibits learning effects and its accuracy was greatly improved after calibration.