Bearing L10 Life Calculator — Basic and ISO 281 Adjusted Bearing Life
Calculate L10h bearing life using dynamic load rating, equivalent dynamic load, rotational speed, bearing type, reliability, and aISO factor.
Enter the known values and review the calculated result
Input parameters
Use consistent values and select the intended engineering units.
Load definition
Bearing parameters
Equivalent load
Load components
Reliability & operating conditions
Results
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Method, application and limitations
Review the calculation method, intended application and engineering assumptions before using the result in a design decision.
Formula and calculation method
L10h formula:
P = Peq
For direct load input:
P = P
For component load input:
P = X · Fr + Y · Fa
When automatic load factors are enabled:
- If Fa / Fr < 0.3, then X = 1 and Y = 0
- If Fa / Fr ≥ 0.3, then X = 0.56 and Y = 1.6
C / P = C / Peq
L10 = (C / P)p
L10,rev = L10 · 106
L10h = L10,rev / (60 · n)
Lna formula:
Lna = a1 · aISO · L10
Lna,rev = Lna · 106
Lna,h = Lna,rev / (60 · n)
Bearing life exponent:
- Ball bearing: p = 3
- Roller bearing: p = 10 / 3
Reliability factor:
- 90% reliability: a1 = 1.00
- 95% reliability: a1 = 0.62
- 96% reliability: a1 = 0.53
- 97% reliability: a1 = 0.44
- 98% reliability: a1 = 0.33
- 99% reliability: a1 = 0.21
where:
- L10h — Basic rating life at 90% reliability (h)
- Lna,h — Adjusted rating life according to ISO 281 (h)
- L10 — Basic rating life (106 revolutions)
- Lna — Adjusted rating life (106 revolutions)
- C — Dynamic load rating (N)
- P — Equivalent dynamic load (N)
- Peq — Equivalent dynamic load calculated from the selected load mode (N)
- Fr — Radial load (N)
- Fa — Axial load (N)
- X — Radial load factor (-)
- Y — Axial load factor (-)
- n — Rotational speed (rpm)
- p — Bearing life exponent (-)
- a1 — Reliability factor (-)
- aISO — Operating condition factor (-)
When to use this calculator
When to use this calculator:
- Estimate basic bearing rating life from dynamic load rating, equivalent dynamic load, bearing type, and rotational speed.
- Compare ball bearing and roller bearing life using the exponent selected by bearing type.
- Calculate adjusted bearing life using reliability level and operating condition factor.
- Convert bearing life from million revolutions to operating hours using rotational speed.
- Calculate equivalent dynamic load from radial and axial load components using radial and axial load factors.
How to interpret the result
L10h bearing life is defined as the basic rating life in operating hours at 90% reliability. Lna adjusted bearing life is defined as the ISO 281 adjusted rating life in operating hours after applying reliability and operating condition factors.
Bearing life depends on the ratio between dynamic load rating and equivalent dynamic load, bearing type, rotational speed, reliability level, and operating condition factor. Increasing dynamic load rating increases bearing life. Increasing equivalent dynamic load decreases bearing life. Increasing rotational speed decreases life expressed in hours.
- Safe — Used when none of the warning, unsafe, or invalid conditions are triggered.
- Warning — Used when dynamic load rating divided by equivalent dynamic load is below 1.5, or when L10h is below 5000 h.
- Unsafe — Used when L10h is below 1000 h, or when adjusted bearing life is below 1000 h.
- Invalid — Used when the selected load mode, bearing type, load values, speed, dynamic load rating to equivalent dynamic load ratio, or load utilization violates the calculator validation rules.
The result is used to evaluate whether the selected bearing has sufficient calculated operating life for the entered load, speed, reliability, and operating condition factor.
Calculation example
Example:
A user needs to estimate the service life of a ball bearing operating in a machine shaft under combined radial and axial load.
- Dynamic load rating: 25 000 N
- Radial load: 5 000 N
- Axial load: 2 000 N
- Load factors: automatic (based on load ratio)
- Rotational speed: 1 500 rpm
- Reliability level: 90%
- Operating condition factor: 1.0
The calculated basic rating life is approximately 9 900 hours, and the adjusted rating life is also approximately 9 900 hours under these conditions.
Assumptions and limitations
- The bearing type is limited to ball bearing or roller bearing.
- The bearing life exponent is 3 for ball bearings and 10 / 3 for roller bearings.
- The equivalent dynamic load is either entered directly or calculated from radial load, axial load, radial factor, and axial factor.
- When automatic load factors are enabled, radial and axial factors are selected from the axial-to-radial load ratio rule implemented in the calculator.
- The reliability factor is selected from the reliability table implemented in the calculator.
- If the operating condition factor is not finite or is not greater than zero, the calculator uses 1.00.