A plan view pattern control method for use in plate rolling called Mizushima Automatic Plan View Pattern Control System (MAS) or Dog Bone Rolling (DBR) was developed. In this method, slab is given a nonuniform thickness profile in the width direction to obtain nonuniform elongation. In order to make the plate more rectangular under various rolling conditions, the prediction of elongation is necessary. In this research, the influence of the width of the dog-bone (overly thick part at the slab width edge) on the fish-tail length (over-elongation at the slab end) is investigated. The fish-tail length increases as the dog-bone width increases and the dog-bone width ratio decreases. These phenomena are related to the following behavior of the restriction of excessive elongation at the dog-bone. As the dog-bone width increases and the dog-bone width ratio decreases, the working length of restricting stress increases. Hence restricting stress is released earlier and the rolling length of fish-tail formation increases. As a result, the fish-tail length increases. Therefore, in the prediction of the plan view pattern, not only the dog-bone thickness, but also the dog-bone width should be considered.