Our study demonstrated that pelvic visceral fat (PVF) and working space (WS) in the pelvic cavity are factors that significantly affect operative time in robot-assisted radical prostatectomy (RARP). Diverse space volumes were measured using the Synapse Vincent® (FUJIFILM, Tokyo) 3D image analysis software. This technology allows calculation of the volume of any space using magnetic resonance imaging (MRI) or computed tomography (CT) scan images. Working space is the area in the pelvis in which surgeons work during RARP. PVF and WS only can be measured using specific software. Therefore, we explored the measurement of pelvic width (PW) and body mass index (BMI) as practical alternatives. BMI and PW were correlated with PVF and WS, respectively.