Bearing Load Calculator
Every Bearing Has an Expiration Date — This Calculates It
Rolling-element bearings don't fail at a fixed point in time; they fail statistically, wearing out through fatigue that accumulates with every revolution under load. The L10 rating life is the industry-standard way of putting a number on that: the number of hours 90% of a population of identical bearings would be expected to survive under a given load and speed.
The Formula
L10h = (L10 × 106) / (60 × N)
C is the bearing's dynamic load rating from its datasheet, P is the equivalent dynamic load actually being applied, and N is rotational speed in rpm. L10 comes out in millions of revolutions before it's converted to hours.
Worked Examples
| Type | Dynamic Rating C | Equivalent Load P | Speed | L10 (million rev) | L10 Life |
|---|---|---|---|---|---|
| Ball (p=3) | 15,000 N | 3,000 N | 1,500 rpm | 125.0 | 1,388.89 hours |
| Roller (p=10/3) | 20,000 N | 4,000 N | 1,000 rpm | 213.747 | 3,562.45 hours |
Because load is raised to the third power (or 10/3 for roller bearings), rating life is extremely sensitive to load — halving the equivalent load multiplies L10 life by roughly eight for a ball bearing.
Where This Calculation Matters
- Bearing selection — comparing candidate bearings against a target service life before committing to a part number.
- Maintenance interval planning — scheduling preventive replacement before the statistical failure window rather than waiting for a breakdown.
- Load path troubleshooting — diagnosing why bearings are failing early by checking whether the actual equivalent load exceeds what was assumed at the design stage.
How to Use This Calculator
- Enter Dynamic Load Rating C (N) from the bearing's datasheet.
- Enter Equivalent Dynamic Load P (N) — the actual combined radial/axial load on the bearing.
- Enter Rotational Speed (RPM).
- Select whether it's a Ball Bearing or Roller Bearing, since each uses a different load-life exponent.
- Select Calculate to get the L10 life in millions of revolutions and in hours.
Related Calculations
If the load itself comes from a rotating shaft, cross-check its sizing with the Shaft Diameter Calculator.