Under the action of a certain load, the number of revolutions or hours the bearing experiences before pitting is called the bearing life. The life of a rolling bearing is defined in revolutions (or hours worked at a given speed) : within this life, a bearing shall undergo initial fatigue damage (peeling or defect) on any of its bearing rings or rolling bodies. However, no matter in the laboratory test or in the actual use, it can be clearly seen that the same appearance under the same working conditions, the actual life of the bearing is very different. In addition, there are several different definitions of the "life" of a bearing, one of which is the so-called "working life", which means that the actual life that a bearing can achieve before it is damaged is caused by wear, and the damage is usually not caused by fatigue, but by wear, corrosion, seal damage, etc.

Due to the difference of manufacturing precision and material uniformity, the life span of the same batch of bearings with the same material and same size will be different even if they are used under the same working conditions. If the statistical life is 1 unit, the longest relative life is 4 units, the shortest is 0.1-0.2 units, and the ratio between the longest and the shortest is 20-40 times.

In order to determine the standard of bearing life, the bearing life is linked with reliability.