Bearing Life Calculator
This bearing life calculator finds the basic rating life of a ball or roller bearing from its dynamic load rating and the equivalent load, using the ISO 281 L10 formula. Add the speed and it returns the life in hours, the life adjusted for higher reliability, and the service life in years at your daily operating hours.
Results
The Bearing Life Calculator is part of our Machinery collection. Browse more machinery to size, convert, and check your work alongside this tool.
What the bearing life calculator does
Rolling bearings wear out by fatigue: after enough load cycles, the raceways start to flake. The L10 life is the number of revolutions that 90% of identical bearings reach before that happens. The bearing life calculator uses the load rating C from the bearing catalog and the equivalent load P on the bearing, applies the ISO 281 life equation, and converts the result to hours and years at your speed and duty.
Bearing life formula
The ISO 281 basic rating life and its conversion to hours:
n is the speed in RPM and a1 the reliability factor: 1 at 90%, 0.64 at 95%, 0.55 at 96%, 0.47 at 97%, 0.37 at 98%, and 0.25 at 99%.
Bearing life calculator example
A ball bearing with C = 30 kN under P = 3 kN at 1,500 RPM:
At 8 hours a day that is about 3.8 years. A roller bearing with C = 52 kN under 6.5 kN at 900 RPM gives 18,963 hours, or 12,136 hours at 95% reliability.
How to use the bearing life calculator
Choose ball or roller bearing. Enter the basic dynamic load rating C from the catalog and the equivalent dynamic load P, both in kN. Enter the shaft speed in RPM, the reliability you need, and the hours of operation per day. Press Calculate to read L10 in million revolutions, L10h in hours, the reliability adjusted life, and the service life in years.
Reading L10 bearing life
L10 is a statistical life: 10% of bearings may fail before it, and half last about five times longer. Compare L10h with the design life your machine needs, commonly 20,000 to 30,000 hours for machines running one shift and 40,000 to 60,000 hours for continuous plant. Because life depends on the load ratio cubed, a small change in load shifts the result a lot: halving the load on a ball bearing raises its life eight times.
When to use an L10 life calculation
- Selecting a bearing size for a new shaft
- Checking a replacement bearing for a heavier load
- Planning maintenance intervals
- Comparing ball and roller bearing options
- Estimating life at a higher reliability for critical machines
Common bearing life calculator mistakes
- Using the static rating C0. Life uses the dynamic rating C.
- Ignoring axial load. Combine it into the equivalent load P.
- Mixing units. Enter C and P in the same unit.
- Treating L10 as a guarantee. It is a 90% survival figure.
Tips for longer bearing life
- Keep lubricant clean; contamination cuts life fast.
- Avoid oversize belt tension.
- Align shafts and housings within the bearing maker limits.
ISO 281 bearing life and the modified life
The basic L10 formula assumes clean lubricant, normal temperature, and correct mounting. ISO 281 adds a modified rating life, Lnm = a1 × aISO × L10, where aISO accounts for lubrication film thickness, contamination, and the fatigue load limit of the material. Good lubrication and clean oil can multiply life several times over the basic figure, while dirty grease or a thin oil film can cut it below. Bearing makers publish calculators for aISO because it depends on their materials. For most design checks, the basic life with a sensible target is enough to choose a size. The shaft that carries the bearing must be sized for the same loads; the shaft diameter calculator handles that check.
How to calculate bearing life with belt and gear loads
Belt drives add a radial load from belt tension, often 1.5 to 2.5 times the effective pull for V-belts and less for timing belts, while helical gears add axial load as well. Work out the shaft reactions at each bearing, combine radial and axial into the equivalent load with the catalog factors, then run the bearing life calculator for each bearing. Check the drive torque first with the torque calculator, since the tooth or belt forces follow from it.
Bearing life hours chart
L10h at 1,500 RPM for different load ratios C/P:
| C / P | Ball bearing L10h | Roller bearing L10h |
|---|---|---|
| 2 | 89 | 112 |
| 3 | 300 | 433 |
| 5 | 1,389 | 2,375 |
| 8 | 5,689 | 11,378 |
| 10 | 11,111 | 23,938 |
| 15 | 37,500 | 92,483 |
Bearing Life Calculator FAQ
What is L10 bearing life?
It is the life in revolutions or hours that 90% of a group of identical bearings reach under the same conditions before fatigue appears.
How do you calculate bearing life in hours?
Compute L10 = (C/P)^p in million revolutions, then multiply by one million and divide by 60 times the speed in RPM. C = 30 kN, P = 3 kN at 1,500 RPM gives 11,111 hours.
Why is the exponent different for roller bearings?
Roller bearings have line contact instead of point contact, which spreads the load and changes how life falls with load, so ISO 281 uses 10/3 instead of 3.
What is the equivalent load P?
It combines radial and axial loads into one radial load, P = X × Fr + Y × Fa, with X and Y factors from the bearing catalog.