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Mechanical reference

Bearing Life Calculator

Turn a bearing’s load rating and the applied load into its L10 life — in millions of revolutions and in hours at speed.

Short answerL10 (millions of rev) = (C ÷ P)^p, with p = 3 for ball bearings and 10/3 for roller bearings. Convert to hours: L10h = L10 × 10^6 ÷ (60 × rpm).

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How it's calculated

L10 is the life 90% of identical bearings will reach under a given load. C is the dynamic load rating from the catalog; P is the equivalent dynamic load combining radial and thrust. Because the exponent is 3 (or 10/3), a small load reduction sharply extends life — halving the load multiplies ball-bearing life about eightfold.

L10 (10^6 rev) = (C ÷ P)^p p = 3 (ball), 10/3 (roller) L10h = L10 × 10^6 ÷ (60 × rpm)
Worked example
  1. Ball bearing, C = 30 kN, P = 3 kN.
  2. L10 = (30/3)³ = 1,000 M rev.
  3. At 1,750 rpm → ≈ 9,520 h.

Reference tables

Load ratio vs L10 life (ball bearing, p = 3)

C ÷ PL10 (10^6 rev)
464
6216
8512
101,000
121,728

A number the tables do not give: cutting the load from P to P/2 multiplies a ball bearing’s L10 life about 8× (2³).

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FAQ

What is L10?

The life 90% of a bearing population is expected to exceed; 10% may fail earlier. It is a statistical rating, not a guarantee for one bearing.

Ball or roller exponent?

Use p = 3 for ball bearings and p = 10/3 for roller bearings — rollers have more contact area, so the exponent is higher.

How do I get equivalent load P?

Combine radial and axial loads with the bearing’s X and Y factors: P = X·Fr + Y·Fa. Pure radial load makes P = Fr.

Does lubrication change life?

Yes — the modified life (Lnm) adds reliability, contamination and lubrication factors on top of L10. Clean, well-lubricated bearings last far longer.

This page is a reference aid. Always verify against the bearing manufacturer data and ISO 281. Figures shown are for orientation, not a stamped design.

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