Bearing life calculator: basic rating life L10 and L10h from load and speed
This bearing life calculator uses the catalogue method of ISO 281 as NSK explains it: L10 = (C/P)^p million revolutions, with p = 3 for ball bearings and 10/3 for roller bearings. A ball bearing with C = 30 kN under P = 3 kN reaches 1000 million revolutions – at 1500 rpm that is 11,111 hours, reached or exceeded by 90 % of identical bearings.
Example: Bearing type: ball bearing (p = 3) · Dynamic load rating C 30 kN · Equivalent dynamic load P 3 kN · Speed n 1,500 rpm · Reliability: 90 % (L10, a1 = 1.00) · Bearing temperature: up to 125 °C (ft 1.00) → Rating life: L10h = 11,111 h. Source: NSK Europe, Technical Insight TI/E/0102 “Bearing life – Calculating the basic fatigue life expectancy of rolling bearings”: L10 = (C/P)^p, L10h = 10⁶/(60n)·(C/P)^p, p = 3 (ball) or 10/3 (roller), reliability factor a1, temperature factor ft (read 09.10.2026). Updated: .
How it is calculated
L10 = (C/P)^p and L10h = 10⁶ ÷ (60 × n) × (C/P)^p. C is the dynamic load rating from the bearing catalogue – the load a bearing can carry for one million revolutions – and P the equivalent dynamic load. The exponent p is 3 for ball bearings and 10/3 for roller bearings. L10 is the life that 90 % of a group of identical bearings reach or exceed.
Examples at 1000 rpm
| C/P | Ball: L10 | Ball: L10h | Roller: L10 | Roller: L10h |
|---|---|---|---|---|
| 2 | 8.0 | 133 h | 10.1 | 168 h |
| 3 | 27.0 | 450 h | 38.9 | 649 h |
| 5 | 125.0 | 2,083 h | 213.7 | 3,562 h |
| 8 | 512.0 | 8,533 h | 1,024.0 | 17,067 h |
| 10 | 1,000.0 | 16,667 h | 2,154.4 | 35,907 h |
L10 in million revolutions. Halving the load gives a ball bearing eight times the life (2³).
Reliability and temperature
For a higher reliability NSK multiplies by a1: 0.64 at 95 %, 0.55 at 96 %, 0.47 at 97 %, 0.37 at 98 % and 0.25 at 99 %. The example bearing (11,111 h) therefore has 7,111 h at 95 % and 2,778 h at 99 %. Above 150 °C the load rating drops: Ct = ft × C with ft 0.95 at 175 °C, 0.90 at 200 °C and 0.75 at 250 °C – at 200 °C the example falls to 8,100 h. For speed ratios in gearboxes use the gear ratio calculator; for force units the force calculator.
Frequently asked questions
How do you calculate bearing life?
L10 = (C/P)^p in million revolutions. C = 30 kN, P = 3 kN, ball bearing: 10³ = 1000 million revolutions.
How do I convert L10 to hours?
L10h = L10 × 10⁶ ÷ (60 × n). 1000 million revolutions at 1500 rpm are 11,111 hours.
What does L10 mean?
The life that 90 % of identical bearings reach or exceed under the same conditions; 10 % fail earlier.
Why 10/3 for roller bearings?
NSK gives the life exponent p = 3 for ball bearings and 10/3 for roller bearings, so at C/P = 5 a roller bearing reaches 213.7 instead of 125 million revolutions.
How do I calculate life at 99 % reliability?
Multiply by a1 = 0.25: 11,111 h become 2,778 h.
Does temperature change the bearing life?
Above 150 °C, yes: the load rating is multiplied by ft (0.90 at 200 °C). In the example the life drops from 11,111 to 8,100 h.
Sources and legal basis
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