Rolling element bearings eventually become worn and develop surface defects, such as spalls, dents, and pits. Previous researchers have used bearings with defects that have sharp 90 ° rectangular edges to develop methods for the estimation of the size of a defect. However, these idealized rectangular defects do not occur in the real world, they are in fact sloped. Tests on bearings with sloped edges on the entry and exit of the defect exhibited similar vibration characteristics as bearing with sharp 90° edges. A new defect size estimation method was developed to improve the accuracy in estimating the size of a defect that has sloping leading and trailing edges. A large dataset was obtained and has been made publicly available.