Objective: A reliable system is necessary for conducting effective dose (E) assessments for diagnosing coronary artery calcium (CAC) for patients with different weights undergoing computed tomography (CT) examination. Materials and Methods: A method has been designed to correlate effective dose and body weight using Rando and polymethylmethacrylate (PMMA) phantoms ranging from 10 to 90 kg. PMMA phantoms were derived from ICRU 48. All scans were conducted on the Toshiba 64-detector row CT scanner with fixed exposure conditions. E was measured in the organs and tissues of interest using thermoluminescent dosemeters (TLDs) and recommended by ICRP 103. Results: E of these phantoms was estimated. The E decreased exponentially in an inverse correlation with increasing patient weight. Conclusion: A simple equation of effective dose relative to different body weight was fitted and can be used as advisory for radiation protection and assessment in Taiwan.