We often encounter the necessity and difficulty for calculation of area and volume of certain object or model; for example, calculation for degree of dural sac compression in lumbar disc herniations or bursting fracture of the spine, for degree of injured area ratio in epiphyseal plate injury, for involved volume of bone and soft tissue tumor etc. So we have made various experiments in calculation of cross sectional areas and total volume for objects or models (cuboid, cylinder, elliptic cylinder, sphere, free form models) using two or three dimensional computerized tomogram, digitizer and auto-CAD (computer aided design) in comparison with principle of Archimedes, with calculation formula of area and volume. The results were as follows; Calculation of cross sectional area and volume using CT scsnner, digitizer and auto-CAD proved very accurate in comparision with other methods.