Bearing L10 Life Calculator
L10 life is the number of revolutions that 90% of a group of identical bearings should reach before fatigue appears. It is a design number, not a guarantee for a single bearing, but it is the starting point for judging whether a bearing is sized sensibly or likely to be the next failure.
Your numbers
From the bearing catalogue.
Combined radial and axial load as an equivalent radial load.
Your results
This is the basic rating life with a simple reliability factor. It excludes the modified life factor aISO for lubrication and contamination, which can raise or lower real life substantially. Use the bearing manufacturer calculation for design decisions.
Life at selected reliability vs equivalent load
Sweeps Equivalent dynamic load P from 2 to 30, holding your other inputs fixed.
Compare calculated life with real failures
Optional review of how bearing replacement history in your ERP can be analysed against design life.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter the basic dynamic load rating C from the catalogue and the equivalent dynamic load P on the bearing. Choose ball or roller type, enter the shaft speed and pick the reliability you need. The calculator returns life in million revolutions, hours and years at your daily running time. The chart shows how quickly life drops as load rises, which is often a revealing picture for overloaded drives.
The formula
Basic rating life is L10 = (C/P) to the power p, in million revolutions, where p is 3 for ball bearings and 10/3 for roller bearings. In hours, L10h = L10 times 1,000,000 divided by (60 times rpm). The adjusted life multiplies by a1 for reliability, as in ISO 281 values such as 0.64 for 95%. A bearing with C/P of 6.9 on a ball bearing at 1480 rpm gets 328 million revolutions or about 3,700 hours.
- Doubling the load cuts ball bearing life by a factor of 8
- Doubling the speed halves life in hours
- Moving from 90% to 99% reliability cuts life to a quarter
Using the result in a reliability program
Compare calculated life with the actual lifetime in your failure history. If bearings fail far earlier than L10h, look for contamination, lubrication problems, misalignment, electrical damage or incorrect loads rather than blaming the bearing quality. If calculated life is shorter than your required life, the answer is a different bearing, lower load or a different arrangement, not a tighter lubrication schedule alone.
Common mistakes
People often use the static rating by mistake, use the shaft load rather than the bearing reaction, forget to combine axial load into P, or mix kN with lbf. P values near a quarter of C are heavy duty. Another is treating L10 as a minimum when it is a statistical median-like value for the 90th percentile of survival.
Frequently Asked Questions
What is the difference between L10 and L10h?
L10 is measured in millions of revolutions, while L10h expresses the same life in operating hours at the given speed. Hours are easier to compare with maintenance history and planned run time.
Is L10 the average life?
No. L10 is the life that 90% of a large group should survive. The median life is about five times higher for ball bearings, and a single bearing can fail much earlier or later.
How do I get the equivalent load P?
P combines radial and axial forces using factors X and Y from the bearing catalogue: P equals X times Fr plus Y times Fa. The factors depend on the bearing type and the ratio of axial to radial load.
Does lubrication change the result?
In real life yes. The ISO 281 modified life includes the aISO factor for lubricant film, cleanliness and fatigue limit. This calculator uses only basic life, so treat it as a first screening value.
Netray can help compare calculated bearing life with actual replacement history held in your ERP maintenance records.
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