In some cases, bearing loads are purely radial or axial; however, in most cases, they are a combination of both. In addition, such loads usually fluctuate in both magnitude and direction. In such cases, the loads actually applied to bearings cannot be used for bearing life calculations; therefore, a hypothetical load that has a constant magnitude, passes through the center of the bearing, and will give the same bearing life that the bearing would attain under actual conditions of load and rotation should be estimated. Such a hypothetical load is called the equivalent load.