Rolling Bearing Life Calculator
Estimate how long a rolling bearing will last under real operating conditions. Enter load ratings, speed, and reliability factor to get predicted bearing life in hours.
About this calculator
Rolling bearing life is predicted using the ISO 281 standard L10 life formula, which relates the dynamic load rating C to the applied load P and operating speed n. The basic rating life in hours is: L10h = (a1) × (C / P)³ × (1,000,000 / (60 × n)), where C is the dynamic load rating (N), P is the applied load (N), n is the speed in RPM, and a1 is the reliability factor (1.0 for 90% reliability by default). The exponent 3 applies to ball bearings; for roller bearings it is 10/3. A higher C/P ratio dramatically extends life — doubling it increases life eightfold. The reliability factor a1 scales life for survival probabilities above 90%, dropping to 0.21 for 99% reliability.
How to use
Suppose a ball bearing has a dynamic load rating C = 20,000 N, an applied load P = 5,000 N, an operating speed n = 1,500 RPM, and a reliability factor a1 = 1.0 (90% reliability). Plug into the formula: L10h = 1.0 × (20,000 / 5,000)³ × (1,000,000 / (60 × 1,500)). First, (20,000 / 5,000)³ = 4³ = 64. Then, 1,000,000 / 90,000 ≈ 11.11. So L10h = 1.0 × 64 × 11.11 ≈ 711 hours. This means 90% of identical bearings running at these conditions are expected to survive at least 711 hours.
Frequently asked questions
What is the L10 bearing life and how is it defined?
L10 life is the number of operating hours (or millions of revolutions) that 90% of a group of identical bearings will reach or exceed before the first signs of fatigue failure appear. In other words, 10% of bearings are expected to fail before this point. It is the industry-standard metric defined by ISO 281 for comparing and selecting bearings. Engineers use L10 as a conservative design target because most applications cannot tolerate widespread early failures.
How does the applied load affect rolling bearing life expectancy?
Bearing life is extremely sensitive to load — it follows an inverse cube law for ball bearings. This means that doubling the applied load reduces bearing life to 1/8 of its original value, while halving the load increases life eightfold. For roller bearings the exponent is 10/3, making them slightly less sensitive but still strongly affected by overloads. This is why accurate load calculation is critical during design, and why shock or misalignment loads that seem modest can drastically shorten service life.
When should I use a reliability factor other than 1.0 in bearing life calculations?
The default reliability factor a1 = 1.0 corresponds to L10 life at 90% reliability, which is appropriate for most general engineering applications. You should reduce a1 when the application demands higher confidence — for example, medical equipment, aerospace, or safety-critical machinery might require 95% or 99% reliability, corresponding to a1 values of approximately 0.62 and 0.21 respectively. Conversely, if early replacement is planned and cost is a concern, a lower reliability target may be acceptable. Always consult the bearing manufacturer's catalog for exact a1 values for your specific bearing series.