What is L10 Life?

Bearings are simple, but they’re essential to keeping machines running. Bearings reduce friction between moving parts and support loads. For industrial equipment, bearings ensure equipment runs smoothly. When a bearing fails too soon, it can lead to expensive downtime. Often, predictive measures can cut down on the likelihood of bearing failure.

Predicting a bearing's lifespan can help in implementing predictive measures. That’s why it’s important to specify how long a bearing will last. One of the best ways to do that is by using the L10 life calculation the preferred method of the American Bearing Manufacturers Association.

What Does L10 Life Mean?

With 90% reliability, L10 life can estimate how long a bearing will last under specific conditions. It means that 90% of bearings in a group will last at least that long when used at a certain speed and load. The other 10% may fail early due to fatigue, which usually shows up as pitting, or small pits on the bearing’s surface.

It’s important to know that L10 life only covers fatigue-related failures. It does not include problems caused by:

• dirt,
• poor lubrication,
• misalignment, or
• general wear and tear.

How Is L10 Life Different from Average Life?

You might also hear the term Mean Time Between Failure (MTBF). This is the average lifespan of a bearing and is usually about five times longer than the L10 life. If you notice big differences in bearing life between machines, it could be because different methods were used to calculate reliability.

Some manufacturers use advanced methods like ISO 281 or their own formulas. These take into account things like oil quality, temperature, and contamination. To reach the predicted lifespan, you’ll need to keep the oil clean and at the right temperature. That might mean using filters or changing the oil often.

When you see a manufacturer quote bearing life, it's important to know how they calculate that value.

How Do You Calculate L10 Life?

The L10 life equation uses three main factors:

• The speed of the shaft (in RPM)
• The bearing’s dynamic capacity (the C Value found in manufacturer catalogs)
• Equivalent radial load: The applied load the bearing sees as a function of actual radial and axial loading as well as bearing geometry.

If you’re using an advanced method, multiply by a factor called aISO, which adjusts for lubrication and contamination.

This calculation gives you a theoretical lifespan. You should be able to calculate, with relative certainty, how many hours 10% of bearings will have failed under the calculated load. Note this equation is theoretical. It won’t reflect issues like poor installation or maintenance. But it is a solid starting point for planning.

Making Informed Bearing Decisions

When choosing a bearing, ask what factors go into the manufacturer's lifespan estimate. Ask what assumptions were made. Was the oil clean? Was the bearing installed correctly? These details matter.

For more help, check out the Regal Rexnord Bearings page. You’ll find manuals, videos, and product specs to guide you.

Last modified: October 22, 2025