RAYSDE BearingsWhat Is the Basic Rating Life L10?
The basic rating life (L10) of a bearing is the number of revolutions (or hours) that 90% of a group of identical bearings will reach or exceed under the same operating conditions. It is the core concept defined by the international standard ISO 281:2007.
The Basic L10 Formula
L10 = (C / P)p × 106 revolutions
- C — basic dynamic load rating (kN), from the catalog
- P — equivalent dynamic load (kN), calculated from actual forces
- p — life exponent: p = 3 for ball bearings, p = 10/3 for roller bearings
Converting to Operating Hours
L10h = L10 / (60 × n)
where n is the rotational speed (rpm). Example: a 6206-2RS1 bearing with C = 19.5 kN, actual load P = 5 kN, n = 1800 rpm:
L10 = (19.5/5)3 × 106 = 58,800 thousand revolutions
L10h = 58,800,000 / (60×1800) = 544 hours
Correction Factors in Real Engineering
1. Reliability correction (a₁)
L10 by default corresponds to 90% reliability. For higher reliability:
| Reliability | a₁ factor |
|---|---|
| 90% (default) | 1.0 |
| 95% | 0.62 |
| 97% | 0.44 |
| 99% | 0.21 |
2. Material & lubrication correction (a₂₃)
Accounts for material quality, lubrication condition and contamination. For normal duty take a₂₃ = 0.8~1.0; with premium lubrication and vacuum-degassed steel it can reach 1.0~1.4.
3. Adjusted rating life
Lnm = a₁ × a₂₃ × L10
Selection Tips
- Light load, high speed: prefer deep-groove ball bearings — low friction, low temperature rise.
- Heavy load, shock: choose cylindrical or tapered roller bearings — high load capacity.
- Misalignment present: choose self-aligning ball or spherical roller bearings.
- Insufficient life?: go up a size, raise the precision grade, or improve lubrication.
Frequently Asked Questions
What exactly is L10 bearing life?
L10 is the basic rating life — the number of revolutions or hours that 90% of a batch of identical bearings will reach or exceed under identical conditions, per ISO 281:2007. Roughly 10% are expected to fail before L10.
How do I convert L10 from revolutions to hours?
Use L10h = L10 / (60 × n), where n is the shaft speed in rpm. For example, L10 = 58.8 million revolutions at 1800 rpm gives about 544 operating hours.
What is the difference between L10 and higher-reliability life?
L10 assumes 90% reliability. Higher reliability (95%, 97%, 99%) applies an a₁ factor below 1.0, which reduces the calculated life accordingly.
Can RAYSDE help with life calculation and selection?
Yes. Send us your load, speed, shaft size and operating temperature and our engineers will run the selection and quote an equivalent product. RAYSDE is an independent supplier and is not affiliated with any original manufacturer.
💡 RAYSDE note: life calculation is the starting point of selection, not the end. Temperature swings, vibration and mounting errors in real service all strongly affect actual life. Contact us for a complete selection plan for your equipment.