Calculate the ISO 281 basic rating life (L10) for ball and roller bearings from dynamic load rating, applied load and shaft speed.
From bearing catalogue
P = X·Fr + Y·Fa from radial/axial loads
Enter C and P from bearing catalogue to calculate L10 life.
ISO 281 basic rating life: L10 = (C/P)^p × 10⁶ revolutions. L10 = 90% survival probability. Actual service life affected by lubrication, contamination, misalignment.
L10 is the basic rating life at which 10% of a group of identical bearings will have failed due to fatigue, and 90% will still be running. It is expressed in millions of revolutions or operating hours. The L10 life is used as a design baseline; actual bearing service life depends heavily on lubrication, contamination, misalignment and temperature.
The C value (dynamic load rating in kN) is published in the bearing manufacturer's catalogue for every bearing designation. It is listed alongside bearing dimensions and is the load under which the bearing achieves exactly one million revolutions of L10 life. SKF, NSK, FAG and NTN all publish this in their catalogues and online product selectors.
P is the hypothetical constant radial load that would cause the same fatigue as the actual combined radial (Fr) and axial (Fa) loads. For radial ball bearings: P = X·Fr + Y·Fa, where X and Y are load factors from the bearing catalogue depending on the Fa/Fr ratio. For purely radial loads with no axial component, P = Fr.