Background: The present study intended to determine and report patient effective dose on the basis of patients and exposure data. Materials and methods: A nationwide computed tomography (CT) survey was provided as a report of patient doses in 2015-2016. Scan details were collected for nearly 2,000 adults and children in four age groups subjected to CT examinations. From total 565 CT scanners in different models in Iran, 120 different scanners were sampled. ImpactDose software was used to calculate the effective dose (ED) by collecting the necessary data also as an alternative fast method, the ED was estimated by multiplying dose length product (DLP) and a conversion factor. Results: There was a high variation in doses received by patients. The estimated EDs by the DLP and conversion factor were lower (except for sinus protocol) than those by ImpactDose software (p=0.014). The mean EDs were 1.09, 0.66, 7.70 and 13.29 mSv for adult patients’ procedures of head, sinus, chest and abdomen-pelvis, respectively. In terms of CTDIvol and DLP, in Iran the mean effective doses were significantly lower than other countries. Conclusion: Publishing guidelines and exposure tables according to patient situations is necessary to decrease variations in doses and exposure parameters. Since the DLP conversion factor leads to a considerable discrepancy in calculating ED, when there is a need for precise dose calculations, the DLP conversion factor should not be used. Furthermore, it is suggested that ED be used as DRL, instead of CTDIvol.