A new multi-scale curved beam based model was developed for piston-ring designs. This paper describes the free-shape, force in circular bore and ovality distributions related parts. Knowing any one of these distributions, this model determines the other two. This tool is useful in the sense that the characterization of the ring is carried out by measuring its ovality distribution which is more accurate than measuring its free shape or force distribution in circular bore. Thus, having a model that takes the ovality as an input is more convenient and useful based on the experiments carried out to characterize the ring.