The measurement of total body calcium is an important tool in the diagnosis and treatment of many diseases associated with bone. This measurement is done by IVNAA or DEXA. A knowledge of normal bone mineral mass for a given person, is necessary to determine whether or not a measured quantity is normal or low. The factors that determine bone mineral mass in a person are not clearly known. IVNAA indicates that bone mineral mass is a function of height but not the age whereas the reverse is indicated by DEXA. In this work, we have measured the bone mineral mass of over 200 normal volunteers by IVNAA and DEXA and have developed a methametical model for DEXA (for lumbar spine and femoral neck) as a function of height, age, weight and years after menopause. In determining the bone mineral mass, height is the predominant factor under 20 years of age and age appers to be the dominant factor for over 20 years. The equation derived is useful in calculating the normal bone mineral mass in a patient against which the measured value can be compared.