Rolling Bearing Life Calculator (L10)

The basic rating life of a rolling bearing in millions of revolutions and in hours.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

The basic rating life L10 is the life that 90 percent of identical bearings reach or exceed under the same conditions. It is L10 = (C / P)^p millions of revolutions, where C is the basic dynamic load rating from the catalogue, P the equivalent dynamic load, and p = 3 for ball bearings and 10/3 for roller bearings.

The life in hours follows from the speed. The calculation is the classic one. Real life also depends on lubrication, contamination, temperature and reliability, which modified rating life methods in the catalogue include.

Formulas used

  • L_{10} = \left(\frac{C}{P}\right)^p\ \text{million revolutions}
  • L_{10h} = \frac{10^6\,L_{10}}{60\,n}

Worked example

With the default numbers in the calculator above:

  1. Life in millions of revolutions: 125 million rev
  2. Life in hours: 1389 hours

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

What does L10 mean?

Ten percent of bearings are expected to fail by that life, and ninety percent to last longer.

Where do I get C?

From the bearing catalogue or data sheet, for the exact bearing number.

How do I find P?

Combine the radial and axial loads with the factors in the catalogue. For a purely radial load, P is the radial load.

Related calculators

Further reading: Shigley, Mechanical Engineering Design (rolling-contact bearings); ISO 281 (the standard itself is licensed).

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