Bearing Life (L10) Calculator

How is bearing life calculated?

The rating life of a rolling bearing is the number of revolutions it can make before the first sign of fatigue on the rolling surfaces. The basic equation in ISO 281 is L10 = (C / P)^p, giving the result in millions of revolutions. C is the dynamic load rating from the catalogue and P is the equivalent dynamic load on the bearing. The exponent is 3 for ball bearings and 10/3 for roller bearings.

Life in operating hours follows from the speed: L10h = 1 000 000 × L10 / (60 × n).

What does L10 mean?

L10 is a reliability limit, not an average. Ninety percent of identical bearings running under the same conditions reach or exceed it. The mean life is several times longer, but how long a single bearing will last cannot be known in advance.

Example

A ball bearing with a dynamic load rating of 30 kN carries an equivalent load of 3 kN at 1500 rpm. The load ratio is 10, so L10 = 10³ = 1000 million revolutions. In hours that is 1 000 000 × 1000 / (60 × 1500) = 11 111 hours.

With 6 kN instead of 3 kN the life would drop to one eighth, 1389 hours. That is why getting the load right matters so much in bearing selection.

Limits

This calculation gives fatigue life only. Real service life often depends on lubrication, contamination, mounting errors and sealing. The modified life calculation in the standard handles these with factors and is done with the manufacturer's catalogue. If there is axial load, calculate the equivalent dynamic load first.