Renal parenchymal volume is important for clinical interpretation. The phantom study was carried out to validate the volume calculation. The volume of kidney phantom was determined using reoriented single photon emission computed tomography (RSPECT). The phantom volume range was 20–300 ml. There are two major factors in the determination of volume which are radioactivity concentration and organ/background ratio. Our results showed that the effect of radioactivity concentration on the volume in the kidney phantom is −3.3 to 7.5% whereas the effect of organ/background ration was only 2.2%. Our relative volume deviation, therefore, from the real volume was 1.43%. We concluded that it is feasible to use kidney volume in clinical work.