Abstract Human organs have a certain dose tolerance to receive X-ray radiation, one of which can be received from radiodiagnostic radiation using a CT scan. The aim of this research is study to estimate the effective dose received by CT scan thorax patients then compare it with the Dose Limit Value (DLV) advised by the Nuclear Energy Regulatory Agency (BAPETEN). An estimated effective dose value can be created by calculating the dosage that an organ got from radiation during irradiation using a CT scan. IndoseCT v20b software and manual calculations using empirical tissue weight factors are used in this study to estimate the effective dose received by CT scan thorax patients. This estimated effective dose is then compared with the Dose Limit Value (DLV) advised by the Nuclear Energy Regulatory Agency (BAPETEN) for CT scan thorax patients. The effective dose also can be used to identify cancer risk factors as well as organs at risk in the chest cavity. The basic patient data for this study, including the computed tomography dose index vol (CTDIvol) and dose length product (DLP) values, were collected through observation. Then, on the basis of patient data from a thorax CT scan, data processing was done using the IndoQCT and IndoseCT v20b software programs as well as manual calculations utilizing empirical tissue weight factors. According to this information, the patient who received the greatest effective dose according to calculations made manually and using the IndoseCT program was 38.61 mSv and 35.75 mSv. The results of this study show that the both effective dose value from the two calculation results is still below the DLV recommended by BAPETEN so it is acceptable and considered safe for patients. The thymus gland, heart, and trachea-bronchi are the three organs that receive the highest effective dose values, which increases the possibility of damage after CT scan of the thorax in patients.