What is L10 bearing life?

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.

What is the difference between L10 and L10a (adjusted) life?

L10 is the basic rating life based solely on the load ratio (C/P) and the life exponent. L10a (or Lna per ISO 281) is the modified rating life that includes additional factors: a1 for reliability other than 90%, and aISO for lubrication, contamination, and fatigue load limit. L10a = a1 × aISO × L10. This calculator computes the basic L10 life.

Why is the life exponent different for ball and roller bearings?

The life exponent p reflects the contact geometry. Ball bearings have point contact (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. These values are established in ISO 281.

How do I determine the equivalent dynamic bearing load P?

The equivalent dynamic load P combines radial (Fr) and axial (Fa) forces into a single value that would give the same bearing life. For radial bearings: P = X·Fr + Y·Fa, where X and Y are factors from the bearing catalog depending on the contact angle and Fa/Fr ratio. For purely radial loads, P = Fr. Always consult the bearing manufacturer's catalog for exact X and Y values.

What is a good L10h value for bearings?

Acceptable L10h depends on the application. General guidelines: 3,000–5,000 hours for household appliances; 10,000–25,000 hours for general industrial machinery running 8 hours/day; 40,000–60,000 hours for continuous 24/7 operation; 100,000+ hours for critical infrastructure like power plants. Machine designers typically aim for 20,000 hours minimum for standard industrial equipment.

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.

ISO 281 Ball & Roller L10 / L10h

Results

Basic Rating Life L₁₀ₕ

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L₁₀ (millions of revolutions)

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L₁₀ (years, 24/7 operation)

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C/P Ratio

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Life Exponent p

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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

Typical Bearing Life Guidelines

Application	Required L₁₀ₕ (hours)
Household appliances	3,000 – 5,000
Electric hand tools	1,000 – 2,000
Agricultural machinery	3,000 – 6,000
Conveyor rollers	20,000 – 30,000
General gearboxes	10,000 – 30,000
Electric motors (general)	20,000 – 40,000
Pumps, compressors	40,000 – 60,000
Critical / continuous 24/7	100,000 – 200,000

Practical Example

Example — 6308 Deep Groove Ball Bearing

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 = 123.23 × 10⁶ = 123,230,000 rev

L₁₀ₕ = 123,230,000 / (60 × 1500) = 1,369 hours

ℹ️ Note: This calculator computes the basic L₁₀ life. For modified life L₁₀ₐ (including lubrication, contamination, and fatigue load limit factors), multiply by a₁ × a_ISO per ISO 281.