Bearing Life Calculator (L10 Rating Life, Hours)
By Santaji GadepatilinUpdated November 3, 2026
Rolling bearings eventually fail by fatigue of the raceways, and their life is quoted statistically as L10 — the life that 90% of identical bearings will reach. This bearing life calculator applies the ISO 281 basic rating life equation L10 = (C ÷ P)^p and converts it into operating hours at the shaft speed.
How to use the bearing life calculator
Choose ball or roller bearing, then enter the basic dynamic load rating C from the catalogue, the equivalent dynamic load P acting on the bearing and the speed. The calculator returns the L10 life in millions of revolutions and in operating hours. To pick a bearing, enter the required hours and clear C to get the load rating you need.
Bearing life formula (ISO 281)
L10 = (C ÷ P)p · L10h = 10⁶ ÷ (60 n) × L10
p = 3 for ball bearings, 10/3 for roller bearings. When both radial and axial loads act, P = X Fr + Y Fa with the X and Y factors from the catalogue.
Example
A deep-groove ball bearing with C = 32.5 kN carries 4 kN at 1,500 rpm:
- L10 = (32.5 ÷ 4)³ = 536.4 million revolutions
- L10h = 10⁶ ÷ (60 × 1500) × 536.4 = 5,960 hours
Life versus load ratio at 1,500 rpm
| C/P | Ball L₁₀ (million rev) | Ball L₁₀h | Roller L₁₀ (million rev) | Roller L₁₀h |
|---|---|---|---|---|
| 2 | 8 | 89 h | 10 | 112 h |
| 3 | 27 | 300 h | 39 | 433 h |
| 4 | 64 | 711 h | 102 | 1,129 h |
| 5 | 125 | 1,389 h | 214 | 2,375 h |
| 6 | 216 | 2,400 h | 392 | 4,361 h |
| 8 | 512 | 5,689 h | 1,024 | 11,378 h |
| 10 | 1,000 | 11,111 h | 2,154 | 23,938 h |
| 12 | 1,728 | 19,200 h | 3,956 | 43,957 h |
Notes
- Modern catalogues add a modified life Lnm = a₁ aISO L₁₀, which accounts for lubrication, contamination and the required reliability.
- Real bearings often fail early from poor lubrication, misalignment or contamination rather than fatigue. On inverter-fed motors, shaft currents from VFDs can also damage the raceways.
Frequently asked questions
What is L10 bearing life?
The number of revolutions (or hours at constant speed) that 90% of a group of identical bearings will complete or exceed before the first sign of fatigue. Median (L50) life is roughly four to five times L10.
What is the bearing life formula?
L10 = (C ÷ P)^p million revolutions, with p = 3 for ball bearings and 10/3 for roller bearings. In hours, L10h = 10⁶ ÷ (60 n) × L10, where n is the speed in rpm.
How does load affect bearing life?
Very strongly. For a ball bearing, doubling the load cuts life to one-eighth; halving it raises life eightfold.
What life should I design for?
Typical targets are 8,000–12,000 h for machines used intermittently, 20,000–30,000 h for 8-hour-a-day machinery, and 40,000–60,000 h or more for continuous 24-hour service such as pumps and fans.