Bearing Life Calculator
Enter the bearing's C rating, the actual applied load and RPM to get L10 life — the standard (C/P)³ fatigue calculation for ball bearings.
Open calculatorLast updated: 2026-09-15
How the calculation works
- Bearing fatigue follows (C/P)^k: halve the load and ball bearing life rises 8-fold.
- L10 means 90% of an identical bearing population exceeds that life — it's statistics, not a guarantee.
- Converting to hours uses the operating speed.
Worked example
Interpreting the result
The cubic law is the designer's lever: modest load reductions buy enormous life. But the model assumes clean lubrication, correct mounting and alignment — contamination and misalignment dominate real failures. For machine design, target L10 ≥ 30,000 h industrial, 100,000+ h for continuous-duty units.
Assumptions
- Constant radial load; combined loads need the equivalent-load (X/Y) method first.
- Proper lubrication, mounting and alignment.
Limitations
- Does not account for contamination, misalignment, shock loads or vibration damage.
- Axial loads on deep-groove bearings need the X/Y equivalent conversion.
L10 life is a probability, not a warranty
The rating life this calculator computes is L10: the hours at which 90% of an identical group of bearings survives. Half the group will outlast the figure substantially; 10% will not reach it. Designing a spindle to its L10 life means one machine in ten fails first — which is why critical machinery uses L1 or L5 life (more conservative) and why a bearing that fails before L10 is not proof of a defective part, while one that fails at 20% of L10 usually indicates contamination, misalignment or overloading rather than a bad calculation.
Frequently asked questions
What does L10 life mean?
90% of identical bearings under identical load will exceed that life before fatigue spalling. It's a 90% reliability rating, not a service interval.
How do I extend bearing life?
Reduce load (larger bearing or better alignment), lubricate correctly, keep contamination out, and avoid shock loading. The cubic law means halving load = 8× life.