In this study, we describe and adapt the relevant methods of computed tomography (CT) and stereology to estimate renal cell carcinoma (RCC) volume and volume ratio and compare the RCC volume estimations with the tumor stage. The study included 126 (82 men, 44 women) patients with RCC. The patients were evaluated by CT. The volume and volume ratio of the entire RCC was estimated by the following formula of Cavalierie's principles. According to TNM (tumor, nodes, metastasis) classification, there were 56 (44.4%), 30 (23.8%), and 40 (31.7%) cases in the stage T1, T2, T3, respectively. The results of the volume measurements which obtained from the Cavalier method were assessed according to the stages and were found as 125.52 +/- 102.18 (25-394) cm(3), as 346.25 +/- 112.55 (181-545) cm(3) and 694.88 +/- 405.46 (142-1546) cm(3) in stage T1, T2 and T3, respectively. The volume ratios between the stages were compared statistically and a significant difference were found between the stage T1 and stage T2, stage T2 and the stage T3 and stage T1 and stage T3, respectively. The average tumor volume ratios was found as 28.44% +/- 14.37% (8.69%-61.26%), 55.42% +/- 12.73% (25.78%-73.86%), and 72.48% +/- 17.15% (48.80%-97.15%) in stage T1, T2 and T3, respectively. The present evaluation of RCC volume can be done on any complete set of CT images, where plane scan distance and magnification factor is known, which already take place on to CT images.