Bearing Life Calculator

Basic rating life from catalog load and real load: L10 in hours, with ball and roller exponents handled.

Calculator

Dynamic load rating C (kN) From the bearing catalog — the 90%-survival load at 1 million revolutions.

Equivalent dynamic load P (kN) P = X·Fr + Y·Fa. Pure radial on a deep-groove ball bearing: P = radial load.

Speed (rpm) Shaft speed under load.

Bearing type Deep-groove and angular-contact are ball; cylindrical, spherical, tapered are roller.

About this calculator

This bearing life calculator applies the ISO 281 basic rating life equation: how long until fatigue spalling starts in 90% of an identical bearing group. It is the fatigue ceiling — contamination and lubrication shortfalls cut real field life below L10. Motor sizing that drives the shaft: motor torque calculator.

Calculation Results

592.6 h

L10 hours · 64.0 million revs · median L50 ≈ 2,963 h

Formula: L10 = (C/P)³ × 10⁶ / (60 × RPM)

(10/2.5)³ × 1,000,000 / 108,000 = 592.6 h. Ball exponent 3 — load ratio drives everything.

How to use this result

Compare against your maintenance cycle, not against infinity: 592 hours at 8 h/day is about 10 working weeks — too short for anything but test rigs. The cube law is your lever: raising the load ratio C/P just 25% (from 3.2 to 4.0) roughly doubles life, and the cheapest wins are load reductions — better balance, lighter preload, cleaner alignment. If the number is embarrassingly small, first question is whether P is real: shock loads and misalignment hide in the gap between the catalog number and the field.

Continue Your Calculation

The load on this bearing comes from the shaft — check the motor side.

Motor torque →

Ball bearing L10 life chart (hours)

L10 = (C/P)³ × 10⁶ / (60 × n). Roller bearings (10/3 exponent) run longer at the same C/P.

Load ratio C/P	900 rpm	1,800 rpm	3,600 rpm
1.5	62.5	31.3	15.6
2.0	148.1	74.1	37.0
2.5	289.4	144.7	72.3
3.0	500.0	250.0	125.0
4.0	1,185.2	592.6	296.3

Bearing life formula

In revolutions: L10 = (C / P)^k million revolutions, with k = 3 for ball and k = 10/3 for roller bearings.

In hours: L10 hours = (C/P)^k × 10⁶ / (60 × n). Example: C = 10 kN, P = 2.5 kN, 1,800 rpm, ball: (4)³ × 1,000,000 / 108,000 = 592.6 h.

The cube law in practice: load ratio 2 gives 8× the life of ratio 1; ratio 4 gives 64×. Halving the load multiplies life by 2³ = 8× (ball) or 2^(10/3) = 10.1× (roller).

Motor side of the shaft: motor torque calculator. Power conversions: HP to kW.

Typical L10 design targets

Application	Common L10 target (h)
Hand tools, intermittent duty	5,000–10,000
General industrial motors (IEC standard basis)	20,000–40,000
Continuous fans, pumps, compressors	50,000–100,000
Critical unattended plant	100,000+

Target against the maintenance cycle you actually run. A 20,000 h bearing in a machine overhauled every 5 years at 4,000 h/yr never reaches its rating in service — spending money on the next rating size is wasted unless duty or reliability requirements grow.

Frequently Asked Questions

How do you calculate bearing life in hours?

L10 h = (C/P)^k × 10⁶ / (60 × RPM), k = 3 ball, 10/3 roller. Example: C 10 kN, P 2.5 kN, 1,800 rpm ball: (4)³ × 10⁶ / 108,000 = 592.6 h.

What does L10 life actually mean?

90% of an identical group reaches or exceeds L10 before fatigue spalling starts. It is statistical, not a warranty: 1 in 10 fails earlier, and the median (L50) runs about 5× longer for ball bearings.

Why does halving the load multiply bearing life by eight?

Ball life scales with the cube of the load ratio: life ∝ (C/P)³. Halving P doubles the ratio, 2³ = 8×. Rollers (10/3): 10.1×. Small load reductions buy enormous life.

What is the difference between L10 and L50 life?

L10 = 90% survival; L50 ≈ 5 × L10 (ball) or ~4 × L10 (roller) is where half survive. Catalogs quote L10 because it is the conservative, spec-friendly number.

When is the basic L10 formula not enough?

When something other than subsurface fatigue limits life: contamination, thin lube film, water, misalignment all cut life below L10. ISO 281's a_ISO modification factor adjusts for these — treat L10 here as the fatigue ceiling, not field life.

How do I handle combined radial and axial loads?

Convert with catalog X/Y factors: P = X·Fr + Y·Fa. Mostly-radial on a deep-groove ball bearing: P ≈ Fr. Angular-contact designs change X and Y substantially with axial share.

Do roller bearings really last longer for the same rating?

They use the 10/3 exponent, so life grows faster as load drops — but their ratings differ for the same shaft size. Compare by catalog C and equivalent P, then apply the right exponent — never one exponent for all types.

What L10 life should I design for?

Common targets: 20,000–40,000 h industrial motors, 50,000+ continuous fans/pumps, 5,000–10,000 hand tools. Match the maintenance cycle you actually run — see the design-target table above.

Review & sources

Reviewed: CalcPanel Rotating Equipment Team

Updated: 2026-11-10