Bearing life L10 calculator
From the catalogue dynamic load rating C, the equivalent load P and the speed, calculate the basic rating life (million revolutions and hours), the adjusted life and the load rating needed for a target life; see in the table how life changes with load.
Life modification
The factors in brackets are commonly quoted ISO 281 values; verify them against your edition of the standard and your catalogue before publishing.
The calculation runs in your browser; the values you enter are not sent anywhere.
- Basic rating life L10h
- 800 hours
- ≈ 0.0913 years (About, in continuous operation)
- Basic rating life L10
- 69.57 million revolutions
- C / P ratio
- 4.113
- Equivalent load P
- 6.2 kN
Dynamic load rating needed for the target life
- Required C
- 93.95 kN
- Ratio to your C
- 368%
The C you entered is below the target; a bearing with a higher load rating or a lower load is needed.
Sensitivity: life as the load changes
| Load | P (kN) | L10h (hours) |
|---|---|---|
| −30 % | 4.34 | 2,331 |
| −20 % | 4.96 | 1,562 |
| −10 % | 5.58 | 1,097 |
| 100 % | 6.2 | 800 |
| +10 % | 6.82 | 601 |
| +25 % | 7.75 | 409 |
| +50 % | 9.3 | 237 |
Assumptions
- Load and speed are constant and the bearing is correctly mounted and lubricated. With varying load and speed, the equivalent load and mean speed must be worked out first.
- Life is a statistic of material fatigue: L10 is the life that 90 % of bearings reach (at most 10 % fatigue earlier); a single bearing can last much shorter or much longer.
- Early failure from wear, contamination, poor lubrication, misalignment or corrosion is outside this calculation; a23 only carries the factor you worked out with the catalogue method.
- The exponent p and the reliability factors are commonly known values; the accuracy of this tool depends on the accuracy of the catalogue values you enter.
L10 = (C/P)^p · L10h = L10 · 10⁶ / (60 · n) · Lnm = a1 · a23 · L10 · P = X·Fr + Y·Fa · required C = P · (Lh · 60 · n / 10⁶ / (a1 · a23))^(1/p)
A helper calculation; verify against the standard and the catalogue before publishing. The catalogue method (for example ISO 281 and the manufacturer's software) treats lubrication, contamination and load limits separately; this tool does not replace it. For critical applications, confirm the bearing selection with the manufacturer.
Let's set up monitoring where the life calculation and vibration measurement are used together.
Request a conversation01
How to use it
A
From your catalogue enter the dynamic load rating C, the speed and the equivalent load (or have it calculated from Fr, Fa, X and Y).
B
Choose the bearing type and the reliability level; enter the life modification factor you worked out from the catalogue for lubrication and contamination, or leave 1.
C
Read L10, L10h and the adjusted life; enter a target life to see the C needed, and use the sensitivity table to see the effect of a load change.
02
What is L10 and what does it tell you?
The basic rating life L10 is the life that 90 % of a group of bearings running under the same conditions reach without fatigue damage. It is calculated in million revolutions as (C/P)^p; at constant speed it is converted to hours by multiplying with 10⁶/(60·n). The exponent is 3 for ball bearings and 10/3 for roller bearings.
Because the exponent is high, load affects life very strongly: for a ball bearing a 26 % increase in load roughly halves the life. The sensitivity table shows this effect with your own values.
03
Reliability and adjusted life
L10 is for 90 % reliability. When a higher reliability is wanted, life is reduced by the factor a1; for 99 % the commonly quoted value is 0.25. The effects of lubrication, contamination and load are handled separately with a23 (a_ISO in ISO 281).
The adjusted life is Lnm = a1 · a23 · L10. This tool does not estimate a23: you must calculate it with the method in your catalogue and enter it; if you have not, leave 1.
04
Calculated life versus actual life
In the field most bearings fail before they fatigue, from lubrication problems, contamination, misalignment or mounting damage. The calculated life is therefore more a yardstick for comparison than a lower limit; it is most useful when comparing two bearing options or two load cases.
Vibration and temperature monitoring show early the failures that fall outside the calculation. When monitoring of a calculated bearing should start is best decided together with the monitoring data.
FAQ
- What is the difference between L10 and L10h?
- L10 is the same life expressed in million revolutions and L10h in operating hours. At constant speed L10h = L10 · 10⁶ / (60 · n).
- How do I find the equivalent load P?
- With purely radial load P = Fr for most bearings. When radial and axial load act together, P = X · Fr + Y · Fa is used; X and Y are given in the catalogue by bearing type and Fa/Fr ratio. This tool holds no such tables, so enter the values from your catalogue.
- When should I use the reliability factor a1?
- When your target is a reliability above 90 %. For example the commonly quoted value is 0.64 for 95 % and 0.25 for 99 %. Verify the values against the edition of the standard and the catalogue you use; manufacturers may apply different methods.
- Why does the P/C ratio matter?
- When the load exceeds half of the dynamic load rating the bearing is heavily loaded; the basic rating life relation may deviate from real behaviour here and static load safety must also be checked. The tool warns when P/C exceeds 0.5.
- Should I replace the bearing when the calculated life is reached?
- Not automatically. L10 is a statistic: 10 % of bearings fail before it and many last much longer. If the replacement decision follows measured vibration, temperature and lubricant condition, both early failures and unnecessary replacements are reduced.
Complete the life calculation with monitoring data
Let's look at which bearings warn before the calculation says so, using vibration and temperature data.