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 basic and modified rating life?

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, where a1 accounts for the selected reliability and aISO for operating conditions including lubrication, contamination and fatigue load limit. This calculator computes only 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 L10h value should I require?

There is no universal acceptable L10h value. The required rating life must come from the machine specification and risk assessment, considering duty cycle, reliability target, maintenance strategy and the bearing manufacturer’s application guidance. Basic rating life is not a guarantee of service life.

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 281:2007 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

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

Worked example — stated catalog rating and load

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 L_nm = a₁ × a_ISO × L₁₀, with factors selected for the required reliability and operating conditions.