L10 bearing life is the number of revolutions (or hours) that 90% of identical bearings will complete before the first sign of fatigue. It is the industry standard for comparing bearing durability.
Basic L10 formula
L10 = (C/P)^p million revolutions
Where: C = dynamic load rating (kN, from the bearing datasheet), P = equivalent dynamic load on the bearing (kN), p = 3 for ball bearings, 10/3 for roller bearings.
What this means for MRO buyers
Higher C means longer life for the same load. When comparing a replacement bearing to the original:
- If the replacement has the same or higher Cr rating, life will be equal or better.
- A 6205 bearing (Cr 14.0 kN) running at 2.0 kN load gives approximately 343 million revolutions L10.
- Converting to hours: at 1500 RPM, that equals about 3,800 hours of continuous operation.
What L10 does NOT tell you
L10 is fatigue life only. It does not account for contamination, poor lubrication, misalignment, or corrosion. These factors cause most real-world bearing failures.
What to ask your supplier
When requesting a quote, provide:
- Operating speed (RPM)
- Radial and axial load (kg or N)
- Operating temperature
- Desired service life (hours)
This lets the supplier confirm the bearing is sized correctly for your application — not just dimensionally compatible.