Bearing Load Calculator
Estimate the L10 bearing life in hours based on radial and axial loads, operating speed, and dynamic load rating. Essential for engineers selecting bearings and predicting maintenance intervals.
About this calculator
Bearing life is predicted using the ISO 281 standard L10 formula, which estimates the number of hours that 90% of a group of identical bearings will survive. The equivalent dynamic load P is first computed from radial and axial components: P = √(radialLoad² + axialLoad²). Then L10 life in hours is: L10 = (C / P)³ × (16,667 / speed), where C is the dynamic load rating (N), P is equivalent load (N), and speed is in RPM. The exponent 3 applies to ball bearings; roller bearings use 10/3. The constant 16,667 converts from millions of revolutions to hours at the given speed. A higher dynamic rating relative to the applied load dramatically extends bearing life — doubling the C/P ratio multiplies life by eight.
How to use
Example: A ball bearing has a dynamic load rating C = 20,000 N, radial load = 3,000 N, axial load = 4,000 N, and operates at 1,500 RPM. Step 1 — Compute equivalent load: P = √(3,000² + 4,000²) = √(9,000,000 + 16,000,000) = √25,000,000 = 5,000 N. Step 2 — Compute L10: L10 = (20,000 / 5,000)³ × (16,667 / 1,500) = 4³ × 11.11 = 64 × 11.11 = 711 hours. This means 90% of these bearings are expected to last at least 711 hours under these conditions.
Frequently asked questions
What does L10 bearing life mean in practical terms?
L10 life is the number of operating hours after which 10% of a population of identical bearings, running under identical conditions, will have experienced fatigue failure. Stated differently, 90% of bearings will survive beyond this point. It is a statistical estimate based on Hertzian contact fatigue theory, not a guaranteed lifespan for any individual bearing. In practice, proper lubrication, cleanliness, and alignment can extend actual bearing life well beyond the calculated L10 value.
How do radial and axial loads affect bearing life differently?
Radial loads act perpendicular to the shaft axis and are the primary load type for most ball and roller bearings. Axial (thrust) loads act parallel to the shaft axis and are handled differently depending on bearing type — deep groove ball bearings can take moderate axial loads, while angular contact or thrust bearings are specifically designed for them. In the equivalent load formula P = √(Fr² + Fa²), both loads combine into a single value; higher combined loads drastically reduce life because of the cubic (or 10/3 for roller bearings) relationship in the L10 equation. Minimizing unnecessary axial loads through proper shaft alignment is one of the most effective ways to extend bearing life.
Why does doubling the dynamic load rating C increase bearing life by so much?
Because the L10 formula raises the C/P ratio to the third power for ball bearings, even modest improvements in the load rating yield large life gains. Doubling C increases (C/P)³ by a factor of 2³ = 8, meaning the bearing lasts eight times longer. This non-linear sensitivity means that selecting a slightly larger bearing with a higher C rating is often more cost-effective than frequent replacement. It also explains why overloading a bearing even briefly can cause disproportionately rapid fatigue damage.