Generally speaking, engineers learn that the bearing L 1 0 life can be estimated using the so called “C/P
method” also known as the “basic rating life” of the bearing. This method finds its root in the 1 940s when
Swedish engineers G. Lundberg and A. Palmgren developed their mathematical model for the bearing life
calculation. In the following decades, this theory has been refined based on a better understanding of the
fatigue life phenomena, as well as improvements in the material, design and manufacturing of the
bearing. These findings were implemented in ISO 281 standard in 1 977, under the title of “adjusted rating
life”. Clearly, bearing manufacturers and industry acknowledged the need to adjust the basic rating life,
taking into account the most important influencing factors affecting bearing performance. Since that time,
further developments have led to what is called today the “modified rating life”, as released in ISO
281 :2007, which includes the a iso life modification factor. In the paper, the succession of equations used
for bearing life ratings are reviewed and current bearing life rating practices are discussed in detail.