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Bearing life L10 calculator

Enter the bearing load rating, loads, speed and required reliability to get L10 life, the ISO 281 modified life and how many years of operation it represents.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

Pre-sizing
Bearing

Example: deep groove ball bearing 6309 (C = 55.3 kN; C0 = 31.5 kN). Use the catalog values of your bearing.

Loads and speed

When Fa/Fr ≤ e, use X = 1 and Y = 0. For deep groove ball bearings, e ranges from 0.2 to 0.45 depending on Fa/C0.

Service factor: 1.0 to 1.2 for smooth machines (motors, pumps); 1.2 to 1.5 for fans and gearboxes; 1.5 to 3 for crushers and shock loads.

Reliability and conditions
—Modified rating life Lnm
—

Life versus load

L10 life in hours for loads from 20% to 200% of the current one, on a log scale.

Tap the chart to see the values.

Share of bearings failed over time

Weibull distribution with β = 1.5, consistent with the ISO 281 a1 factor.

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The report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. In the print dialog, choose Save as PDF.

Method, assumptions and references

Equations used

Equivalent load: P = max(X·Fr + Y·Fa, Fr) × service factor
L10 = (C ÷ P)ᵖ [million revolutions], p = 3 (ball) or 10/3 (roller); L10h = L10 × 10⁶ ÷ (60 × n)
Lnm = a1 × aISO × L10h; a1 = 0.95 × [ln(100/R) ÷ ln(100/90)]^(1/1.5) + 0.05
Static safety: s0 = C0 ÷ P0, with P0 = max(Fr, 0.6·Fr + 0.5·Fa) for ball bearings (ISO 76)

Assumptions and limits

  • Constant load and speed; for variable duty use the cubic mean load and weighted mean speed.
  • The aISO factor is entered by the user; the full ISO 281:2007 calculation depends on lubricant viscosity, contamination (eC) and the catalog fatigue limit Cu.
  • The calculated life is material fatigue life; failures from poor lubrication, gross contamination, misalignment or mounting are not included.

Standards and technical documents

  • ISO 281:2007: Rolling bearings — Dynamic load ratings and rating life
  • ISO 76:2006: Rolling bearings — Static load ratings
  • ISO/TS 16281:2008: Methods for calculating the modified reference rating life
  • ABNT NBR ISO 281: Rolamentos — Capacidade de carga dinâmica e vida nominal

U.S. regulations

  • OSHA 29 CFR 1910.219: guarding of mechanical power-transmission apparatus
  • No legal minimum bearing life; design life comes from equipment standards (for example API 610 and NEMA MG 1)

Frequently asked questions

How do you calculate bearing L10 life?

L10 = (C ÷ P)³ million revolutions for ball bearings, with exponent 10/3 for roller bearings. For hours, multiply by 10⁶ and divide by 60 times the speed. A 6309 under 6.5 kN at 1,480 rpm lands near 6,900 h.

What does L10 mean?

It is the life that 90% of identical bearings reach before fatigue. So 10% fail earlier; the mean life of a batch is about five times L10.

How can bearing life be extended?

Load reduction has a cubic effect: 20% less load almost doubles life. Correct lubrication and cleanliness raise the aISO factor, which can multiply life several times.