The various functions required for rolling bearings vary: depending on the bearing application. These functions must be performed for a long time. Even if bearings are properly installed and operated correctly, they end up not performing satisfactorily with increased noise and vibration, loss of accuracy in running, grease deterioration or fatigue spalling of the rolling surfaces. Bearing life, in the broadest sense, is the term bearing continues to meet its required function during operation. This bearing life may be defined as noise life, wear life, grease life or rolling fatigue life, depending on which cause the bearing is lost in service.

In addition to the natural deterioration of the bearing's functional failure, the bearing may fail under conditions such as scoring rings, damage to seals or cages or other damage occurs. These conditions should not be construed as normal bearing failures as they often occur as a result of bearing selection errors, improper design or manufacture of the bearing surroundings, improper installation or insufficient maintenance. Rolling fatigue life and basic rating life, when a rolling bearing is operated under load, the raceways of the inner and outer rings roll and the elements are subjected to repeated cyclic stress. Due to metal fatigue at the rolling contact surfaces, the raceways and rolling elements, scaly particles may separate from the bearing material. This phenomenon is called "peeling". Rolling fatigue life is represented by the total number of revolutions at which point the bearing surface will begin to peel off stressed. This is called fatigue life.

The various functions required by rolling bearings vary: even bearings that appear to be the same are of the same type, size and material, and are processed by the same heat treatment, etc., rolling fatigue life varies greatly under the same operating conditions. This is because the spall fatigue of a material is affected by many other variables. Therefore, "Basic Rating Life" where rolling fatigue life is considered a statistical phenomenon is superior to actual rolling fatigue life. It is assumed that some bearings of the same type are operated individually under the same conditions. After a period of time, 10% of which failed due to rolling fatigue induced spalling. Revolution at the moment is defined as base rating, life or if speed does not change, base rating life is often expressed in total operating hours when 10% of the bearing becomes inoperable due to spalling. The basic rating life is usually the only consideration when determining bearing life.