The calculation of an individual’s reference weight utilizes diameter measurements (the distance between two bony landmarks) to estimate an appropriate (or normal) body weight based on skeletal size. 1 The reference weight is based on the assumption that diameters and height reflect frame size. In adulthood, frame size provides a stable characteristic from which to estimate how much an individual should weigh with respect to the size of his or her skeleton. The reference weight is the average weight for an adult with a given frame size. Thus, the reference weight can serve as the basis for determining whether an individual is underweight or overweight based on his or her frame size.