Bearing L10 Life Calculator (ISO 281 Basic Rating Life)
The L10 life of a rolling bearing is the number of revolutions that 90% of a large group of identical bearings reach before fatigue spalling appears. Enter C, P and speed to get life in hours and years, and see how life collapses as load rises.
Your numbers
From the bearing catalogue or datasheet.
Combined radial and axial load converted to one equivalent value.
Your results
Basic rating life only. It ignores lubrication film, contamination and misalignment (the ISO 281 a_ISO modifier). Use the bearing maker's tool for final design decisions.
Rating life (hours) vs equivalent load
Sweeps Equivalent dynamic load P from 1 to 20, holding your other inputs fixed.
Bearing life vs actual failures review
Optional: compare calculated L10 against failure history in your ERP work orders.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Take the basic dynamic load rating C from the bearing datasheet and compute the equivalent dynamic load P from your radial and axial forces using the X and Y factors in the catalogue. Enter shaft speed, choose ball or roller exponent, and pick the reliability you need. The result is shown in million revolutions, operating hours and calendar years at your duty cycle. The chart sweeps P so you can see the sensitivity of life to load.
The formula behind it
The basic rating life is L10 = (C / P) to the power p, in million revolutions, with p = 3 for ball bearings and 10/3 for roller bearings. Hours follow from L10h = L10 x 1,000,000 / (60 x n) with n in rpm. The reliability factor a1 scales life for survival probabilities above 90%. Because of the exponent, a 20% increase in load cuts life by roughly 40% on a ball bearing.
- Life falls with the cube of load for ball bearings
- Doubling speed halves life in hours but not in revolutions
- a1 = 1 corresponds to the familiar L10 definition
Reading the result and common mistakes
A computed life is a statistical figure, not a guarantee. Many field failures happen far earlier because of contamination, poor lubrication, misalignment or electrical fluting, none of which appear in basic rating life. Use L10 to compare design options and to set a plausible replacement or inspection horizon, then let condition monitoring tell you when an individual bearing is actually degrading.
- Using the static rating C0 instead of the dynamic rating C
- Forgetting to convert axial load into equivalent load P
- Mixing kN and N between C and P
- Treating a 30-year computed life as proof that bearings will not fail
Frequently Asked Questions
What does L10 mean?
L10 is the life that 90% of a large group of identical bearings, run under the same conditions, will reach or exceed before the first sign of material fatigue. Ten percent are expected to fail sooner.
Why is the exponent 3 for ball bearings?
It comes from the empirical relationship between load and fatigue life of point-contact bearings. Roller bearings have line contact, which gives a slightly higher exponent of 10/3.
Is L10h the same as time to failure?
No. It is a statistical rating life for a group. Individual bearings can fail much earlier or last several times longer, and real life depends on lubrication, cleanliness and alignment.
How do I get P if I have radial and axial loads?
Use P = X Fr + Y Fa with the X and Y factors listed in the bearing catalogue for your bearing type and the ratio Fa / Fr. For pure radial load on many bearings, P equals Fr.
Netray can pull running hours and failure history from your ERP maintenance module so measured bearing life can be compared against these calculated figures.
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