Bearing life (L10) calculator
Pick a bearing or type its dynamic load rating C, enter the equivalent load P and the speed, and get the basic rating life in million revolutions and in hours.
Worked example
Inputs: 6308 deep groove ball bearing (C = 42.3 kN), equivalent load P = 8.5 kN, 1,500 rpm, 90% reliability.
- C / P = 4.98, life exponent p = 3.
- 0.2 years of 24-hour running at the basic reliability.
This is the live calculator output for the default values above.
The formula
L10 = (C / P)p million revolutions, with p = 3 for ball bearings and 10/3 for roller bearings. L10h = L10 × 1,000,000 ÷ (60 × rpm) hours. L10 is the life that 90% of a group of identical bearings reach or exceed. For higher reliability multiply by the factor a1: 0.64 for 95%, 0.55 for 96%, 0.47 for 97%, 0.37 for 98% and 0.25 for 99%.
What it leaves out
Basic life assumes a clean bearing, correct fit, good alignment and adequate oil film. Real life can be longer or much shorter. The Verify a Bearing tool in Rotec AI adds the oil film (kappa), contamination and the SKF life modification factor, and checks relubrication.
How to find P
P is the equivalent dynamic load, combining radial and axial loads. See the load calculator guide for where the loads on a shaft come from.
Browse bearings with rated life
Each bearing page has a life table: for example the 6308, 6205 or 22210 E.
Related tools and guides
Questions
How do you calculate bearing life?
L10 = (C/P)^p million revolutions, where C is the dynamic load rating, P the equivalent load, p = 3 for ball and 10/3 for roller bearings. Divide by 60 × rpm for hours.
What does L10 life mean?
It is the life reached or exceeded by 90% of identical bearings under the same conditions.
Why is my bearing failing before its calculated life?
Contamination, poor lubrication, bad fits and misalignment cut life far below the basic calculation. See the failure mode guides.
Results are starting points from standard engineering practice. Confirm critical selections with the bearing or lubricant maker.