Free Engineering Tool
Bearing L10 Life Calculator
Calculate bearing basic rating life L10 per ISO 281. Enter the dynamic load rating C, equivalent dynamic load P, bearing type, and rotational speed.
Results
Applicability warning: C/P is below 2. Public manufacturer guidance states that conventional rating-life theory is no longer fully valid in this range. The mathematical result is shown, but bearing-specific guidance and a more complete analysis are required.
Basic Rating Life (ISO 281)
The basic rating life in revolutions:
The basic rating life in hours:
- C — basic dynamic load rating (kN) from bearing catalog
- P — equivalent dynamic bearing load (kN)
- n — rotational speed (RPM)
- p — life exponent: p = 3 for ball bearings, p = 10/3 for roller bearings
Choosing a Required Life
ISO 281 supplies a rating-life calculation, not a universal minimum life for each machine type. Select the required life from the machine specification and risk assessment, using the actual duty cycle, reliability target, maintenance strategy and bearing manufacturer’s application guidance.
Scope: Basic rating life is a statistical fatigue rating under conventional conditions. ISO 281 does not address every service-life cause; wear, corrosion and electrical erosion can end service life earlier.
Practical Example
Given: C = 42.3 kN, P = 8.5 kN, Speed = 1500 RPM, Ball bearing (p = 3)
C/P = 42.3 / 8.5 = 4.976
L₁₀ = (4.976)³ × 10⁶ = 123.24 × 10⁶ = 123,244,000 rev
L₁₀ₕ = 123,244,000 / (60 × 1500) = 1,369 hours
ℹ️ Note: This calculator computes basic L₁₀ life only. ISO 281 expresses modified rating life as Lnm = a₁ × aISO × L₁₀, with factors selected for the required reliability and operating conditions.
L10 life is the basic rating life defined by ISO 281 — the number of revolutions (or hours at a given speed) that 90% of a group of identical bearings will complete or exceed before the first evidence of fatigue damage appears. In other words, there is a 10% probability of failure before L10 is reached.
It is the industry-standard metric for comparing and selecting bearings.
L10 is the basic rating life based on C/P and the life exponent. ISO 281 expresses modified rating life as Lnm = a₁ × aISO × L₁₀.
The factors account for the selected reliability and operating conditions including lubrication, contamination and fatigue load limit. This calculator computes only basic L10 life.
The life exponent p reflects the contact geometry between rolling elements and raceways. Ball bearings have point contact (small elliptical contact area), giving p = 3. Roller bearings have line contact (rectangular contact area), giving p = 10/3 ≈ 3.333.
The higher exponent for rollers means their life is more sensitive to load changes — a small load increase causes a proportionally larger reduction in life compared to ball bearings.
Equivalent dynamic load reduces the actual load case or duty cycle to the load used by the rating-life equation. The applicable equation, factors and thresholds depend on bearing type, arrangement, load direction and manufacturer data.
Use the catalog method for the exact bearing and combine variable operating conditions correctly; P = X·Fr + Y·Fa is not a universal one-line rule for every bearing and load case.
There is no universal acceptable value. Derive the requirement from the machine specification and risk assessment, including duty cycle, reliability target, maintenance strategy and bearing manufacturer guidance.
Basic rating life is a statistical fatigue rating, not a guarantee of actual service life; wear, corrosion, electrical erosion and other mechanisms can end service life earlier.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional portable balancers, vibration analyzers, and condition monitoring systems. Extend bearing life through precision balancing. Used in 50+ countries.
