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August 2026 14 min read

Bearing Life Calculator

Free online Bearing Life Calculator for mechanical engineering. Compute L₁₀ and L₁₀h bearing life in revolutions and hours using ISO 281 with reliability adjustment factors for ball and roller bearings.

Bearing Life Calculator

Bearing Loading Details

Unit System

Force unit for C, P and C₀ (math is unit-agnostic as long as all three match)

Dynamic Load Rating C (kN)
kN

Basic dynamic load rating from the manufacturer catalogue

Equivalent Dynamic Load P (kN)
kN

Combined radial/axial load P = XF_r + YF_a

Static Load Rating C₀ (kN)
kN

Basic static load rating for deformation check

Rotational Speed (RPM)
RPM

Operating speed of the shaft

Bearing Type
Ball (p=3) Roller (p=10/3)
Target Reliability

Higher reliability reduces the adjusted life via the a₁ factor

Decimal Precision
Auto-calculate instantly

Basic Rating Life L₁₀

694hours

L₁₀ basic rating life at C/P = 5.00, ball bearing, 3,000 RPM.

Bearing life and static safety adequate
Dynamic Load C

25,000kN

Equivalent Load P

5,000kN

Life Exponent p

3.00

L₁₀ (revolutions)

125,000,000rev

L₁₀h (hours)

694h

Adjusted Life L_na

694h

Reliability Factor a₁

1.00

Static Safety s₀

3.00

Dynamic Load C

25,000kN

Basic dynamic load rating

Equivalent Load P

5,000kN

Combined radial/axial load

Life Exponent p

3.00

Ball (p=3)

L₁₀ (revolutions)

125,000,000rev

Basic rating life in revolutions

L₁₀h (hours)

694h

Basic rating life in operating hours

Adjusted Life L_na

694h

At 90% reliability (a₁=1)

Reliability Factor a₁

1.00

Reduction from L₁₀ baseline

Static Safety s₀

3.00

C₀ / P₀

Result Summary

Dynamic Load Rating C25,000 kN
Equivalent Load P5,000 kN
Life Exponent p3 (ball)
L₁₀ (revolutions)125,000,000 rev
L₁₀ (hours)694 h
Adjusted Life L_na694 h
Reliability90% (a₁=1)
Static Safety s₀3.00
VerdictAdequate
Estimated Result — Results follow the ISO 281 L₁₀ methodology with material (a₂) and operating-condition (a₃) factors held at 1.0 (standard steel, clean lubrication). Real bearings deviate with contamination, misalignment, variable loading and specialist steels — consult manufacturer catalogues and apply code/relubrication factors before final selection.

Interactive Diagram

Radial / axial load Rolling elements Status (s₀)

Cross-section updates with your inputs — the corner badge shows the static safety factor and overall adequacy.

Visualizations

Adjusted Life at Selected Reliabilities (hours)

694h90%
431h95%
368h96%
306h97%
229h98%
146h99%

Static Safety Factor Utilization

C₀ / P₀3

Formula

The basic rating life L₁₀ follows the ISO 281 load-life relationship: life scales with the load ratio raised to the fatigue exponent p. Converting revolutions to hours divides by 60·N. The adjusted life L_na multiplies L₁₀ by reliability, material and operating-condition factors for a duty-specific prediction.

L₁₀ = (C/P)^p · 10⁶ rev | L₁₀h = L₁₀ / (60 · N)

Alternative Form

L_na = a₁ · a₂ · a₃ · L₁₀ (adjusted rating life)

Variables

SymbolNameUnitDescription
CDynamic load ratingkN / lbfBasic dynamic load rating from the manufacturer catalogue
PEquivalent dynamic loadkN / lbfCombined radial + axial load (P = XF_r + YF_a)
pLife exponent—3 for ball bearings, 10/3 for roller bearings
NRotational speedRPMOperating speed of the shaft
a₁Reliability factor—1.0 at 90%, 0.62 at 95%, 0.21 at 99%
a₂Material factor—1.0 for standard 52100 steel; higher for vacuum-degassed
a₃Operating condition factor—1.0 for clean lubrication; lower for contamination
L₁₀Basic rating liferevLife that 90% of bearings reach or exceed
L₁₀hBasic rating lifehoursL₁₀ expressed in operating hours

Explanation

Each bearing type has a characteristic fatigue exponent: ball bearings (point contact) use p = 3, roller bearings (line contact) use p = 10/3, making them more load-sensitive. The L₁₀ life assumes 90% reliability; higher reliability cuts available life through the a₁ factor. The adjusted life L_na folds in material and lubrication quality to give a realistic, duty-specific figure, while the static safety factor s₀ guards against permanent deformation when the bearing is stationary or shock-loaded.

Derivation

The ISO 281 relationship derives from the Lundberg–Palmgren fatigue model, where the probability of survival to life L under load P is governed by a Weibull distribution with slope e ≈ 1.5. Integrating the sub-surface stress-life relation yields L ∝ (C/P)^p · 10⁶ revolutions, with p = 10/3 for roller and p = 3 for ball contact derived from the contact-stress exponent. Hours follow from L/(60N), and reliability adjustment uses the quantile L_n = a₁·L₁₀ with tabulated a₁ values.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Identify the bearing type to set the fatigue life exponent.

p = 3 (ball) ; p = 10/3 (roller)
Bearing type:Ball
Intermediate: Exponent p = 3.000
Result: Life exponent selected
Step 2

Compute the basic rating life in revolutions using the load ratio.

L₁₀ = (C/P)^p × 10⁶ rev
C/P:5.00
p:3.000
Intermediate: (5.00)^3.000 × 10⁶
Result: L₁₀ = 125,000,000 rev
Step 3

Convert revolutions to operating hours at the running speed.

L₁₀h = L₁₀ / (60 · N)
N:3,000 RPM
60·N:180,000
Intermediate: 125,000,000 / 180,000
Result: L₁₀h = 694 h
Step 4

Apply the reliability factor to obtain the adjusted rating life.

L_na = a₁ · a₂ · a₃ · L₁₀
a1:1
a2:1
a3:1
rel:90%
Intermediate: a₁·a₂·a₃ = 1
Result: L_na = 694 h
Step 5

Evaluate the static safety factor against the static load rating.

s₀ = C₀ / P₀
C0:15,000 kN
P0:5,000 kN
Intermediate: 15,000 / 5,000
Result: s₀ = 3.00 → Adequate
Step 6

Compare results to application targets and standards.

Check L_na ≥ target hours ; s₀ ≥ 1.0
Intermediate: Reliability 90%, adjusted life 694 h
Result: Verdict: Design adequate
Final Answer
694 hours

Worked Examples

See how the calculator works with different scenarios.

Scenario

A small ball bearing in a light-duty conveyor idler running at moderate speed.

Inputs

Bearing type:Ball (p=3)
C:25 kN
P:5 kN
C₀:15 kN
N:3000 RPM
Reliability:90%

Calculation

L₁₀ = (25/5)³ × 10⁶ = 125 × 10⁶ rev; L₁₀h = 125×10⁶ / (60×3000) = 694 h; s₀ = 15/5 = 3.0

Result

L₁₀ ≈ 694 h, L_na = 694 h (90%), s₀ = 3.0 (good)

Interpretation

Static safety is comfortable, but the fatigue life is short — acceptable only for intermittent or low-duty service.

Understanding Your Result

Your Result: 694 hours

Typical range: Electric motors target 10,000–30,000 h; pumps and gearboxes 20,000–50,000 h; wind turbines 100,000–200,000 h. Your adjusted life is 694 h at 90% reliability, with s₀ = 3.00.

What This Means

Your ball bearing delivers a basic rating life of 694 hours (125,000,000 revolutions), dropping to 694 adjusted hours at 90% reliability. The static safety factor is 3.00.

Why It Matters

Bearing failure is the most common cause of rotating-equipment downtime. Predicting L₁₀ and adjusted life lets you size bearings that meet service-interval targets, while the static safety factor prevents brinelling during standstill or shock loading.

Professional Interpretation

Both fatigue life and static safety are comfortable. Confirm lubrication κ and contamination class — improving a₃ could substantially extend service life at little cost.

Load Ratio Sensitivity

Doubling the load ratio C/P raises life by 2^3.00 ≈ 8.0×. Your ratio is 5.00, the dominant driver of the 694 h result.

Reliability Adjustment

At 90% reliability a₁ = 1.00, so the adjusted life L_na = 694 h versus the L₁₀ baseline of 694 h.

Static Deformation Check

s₀ = C₀/P₀ = 3.00. Values below 1.0 risk permanent raceway deformation (brinelling); 1.0–1.5 is the normal-duty floor.

Recommendations

  • •Match the bearing type to the load: roller bearings for high radial loads, ball bearings for high-speed or combined loads.
  • •At 90% reliability the adjusted life is 1.00× the L₁₀ — raise reliability only if the application truly needs it, since life drops sharply.
  • •Keep contamination out: sealed or shielded bearings and clean lubrication protect the a₃ factor and can multiply service life.
  • •Document the assumed X/Y factors and load combination — reviewer traceability matters for rotating machinery.

Educational Content

Introduction

Rolling bearings are the quiet workhorses of every rotating machine — motors, gearboxes, wheels, spindles and turbines all depend on them. A bearing life calculator translates catalogue load ratings and operating conditions into a statistically meaningful prediction of how long a bearing will run before fatigue, which is the foundation of reliable rotating-equipment design.

Concept Explanation

Bearing fatigue life follows the ISO 281 relationship L₁₀ = (C/P)^p · 10⁶ revolutions, where the load ratio C/P is raised to a fatigue exponent p (3 for ball, 10/3 for roller contact). Hours come from dividing by 60·N. Because failure is statistical, the L₁₀ life is defined as the life 90% of identical bearings survive. Higher reliability requirements apply the a₁ factor (0.62 at 95%, 0.21 at 99%), while material (a₂) and lubrication/contamination (a₃) factors produce the adjusted life L_na. A separate static safety factor s₀ = C₀/P₀ guards against permanent deformation when the bearing is stationary or shock-loaded.

Applications

▸Sizing bearings for electric motors, pumps and fans
▸Gearbox and transmission bearing selection
▸Wind-turbine and renewable-energy drivetrains
▸Machine-tool spindle and precision-rotation design
▸Automotive wheel hubs and powertrain bearings
▸Aerospace and medical equipment requiring high reliability

Benefits

  • •Predicts service intervals before hardware is built
  • •ISO 281 basis accepted across industry and standards
  • •Handles both ball and roller bearing fatigue exponents
  • •Includes reliability and static-safety adjustments in one tool
  • •Instant sensitivity to load ratio and speed

Limitations

  • •Assumes a₁·a₂·a₃ with a₂ = a₃ = 1.0 (standard steel, clean lubrication)
  • •Uses a single equivalent load; variable-mission loading needs equivalent-load integration
  • •Ignores misalignment, fit, clearance and housing effects
  • •Excludes lubrication film (κ) and contamination (e_c) detail of full ISO 281:2007
  • •Statistical L₁₀ says nothing about a single bearing’s exact failure time

Best Practices

  • •Compute the true equivalent load P = XF_r + YF_a from manufacturer X/Y tables, not just the radial load
  • •Specify reliability to match duty: 90% standard, 95% pumps, 98–99% critical/aerospace
  • •Keep static safety ≥ 1.5 (or 2.5–4.0 under shock) to avoid brinelling
  • •Pair life prediction with a lubrication plan that maintains κ ≥ 1
  • •Re-evaluate when speed, load or duty cycle change during service

Common Misconceptions

Myth: A higher L₁₀ always means a better bearing.
Truth: L₁₀ depends heavily on the assumed load ratio C/P; comparing bearings only makes sense at the same equivalent load and reliability.
Myth: Ball and roller bearings behave the same.
Truth: Roller bearings use p = 10/3, so life is far more sensitive to load changes — doubling load cuts roller life ~10× versus ~8× for ball bearings.
Myth: If it spins, the static rating does not matter.
Truth: Stationary or shock-loaded bearings can brinell (permanently deform) even at zero fatigue damage; s₀ must stay above 1.0.
Myth: 90% reliability is always enough.
Truth: For critical equipment 90% L₁₀ means 1 in 10 bearings fails early; 99% is common in aerospace and medical applications.

Practical Tips

  • •Current static safety is 3.00. Aim for ≥ 1.5 in normal duty and 2.5–4.0 where shock loads occur.
  • •Small increases in the load ratio C/P dramatically extend life — choosing the next larger bore is often the cheapest reliability gain.
  • •Speed only affects hours, not revolutions: raising N shortens L₁₀h by the same factor but leaves L₁₀ unchanged.
  • •For variable duty, first reduce the load spectrum to a single equivalent P before using this calculator.
  • •Remember L₅₀ ≈ 5 × L₁₀ — half of all bearings typically outlive five times the rated life.

Common Mistakes

Using only the radial load for P
Combine radial and axial loads with the manufacturer X and Y factors: P = XF_r + YF_a. Ignoring thrust can drastically under-predict life.
Treating reliability and L₁₀ as interchangeable
L₁₀ is the 90% life. Selecting 99% reliability uses a₁ = 0.21 — the available life collapses to ~21% of the L₁₀ value.
Neglecting the static safety factor
A great fatigue life is useless if s₀ < 1.0 and the bearing brinells under standstill or shock load. Always check s₀.
Mixing unit systems for C and P
C and P must use the same force unit (both kN or both lbf). Mismatched units silently destroy the load ratio.
Assuming a₂ = a₃ = 1.0 always
Poor lubrication or contamination can drop a₃ to 0.1–0.5, cutting life by 2–10×. Verify κ and cleanliness for critical machines.

Assumptions

This calculator makes the following assumptions to provide estimates:

ISO 281 L₁₀ model: Life follows the Lundberg–Palmgren fatigue relation with a Weibull slope of ~1.5; 90% survival defines the basic rating life.
Constant equivalent load: A single steady equivalent load P is assumed; variable loads must be reduced to an equivalent before calculation.
Standard material & lubrication: Material factor a₂ and operating-condition factor a₃ are taken as 1.0 (standard 52100 steel, clean lubrication).
No misalignment or fit effects: Internal clearance, misalignment, housing fit and preload are not modelled and are left to the designer.
Negligible external heating: Operating temperature is assumed within standard bearing-steel limits so hardness and viscosity are unaffected.

Limitations

Be aware of these limitations when using this calculator:

Single load case: Only one equivalent load and speed are handled; duty-cycle and spectrum loading need equivalent-load integration.
a₃ / κ not detailed: Full ISO 281:2007 lubrication (κ) and contamination (e_c) factors are simplified to a₃ = 1.0.
No system-life coupling: Bearing sets and shaft systems (where L_sys < any individual life) are not combined here.
Statistical, not deterministic: L₁₀ is a 90% survival estimate; an individual bearing may fail much sooner or later.
Excludes specialised types: Needle, spherical and thrust bearings need type-specific C, X and Y data from the manufacturer.

Frequently Asked Questions

Answers to common questions about this calculator.

What is bearing life?
Bearing life is the number of revolutions or operating hours a bearing can achieve before fatigue failure occurs. It is statistically defined because bearing failure follows a probability distribution. The L₁₀ life (basic rating life) is the life that 90% of a group of bearings will reach or exceed.
What is L₁₀ bearing life?
L₁₀ life, also called basic rating life, is the life in revolutions or hours that 90% of a group of apparently identical bearings will achieve or exceed under identical operating conditions. It is the standard industry metric for bearing fatigue life prediction per ISO 281.
How is bearing life calculated?
Bearing life is calculated using L₁₀ = (C/P)^p × 10⁶ revolutions, where C is the dynamic load rating, P is the equivalent dynamic load, and p is the life exponent (p=3 for ball bearings, p=10/3 for roller bearings). Life in hours: L₁₀h = L₁₀/(60·N).
What is the dynamic load rating C?
The dynamic load rating C (basic dynamic load rating) is the calculated constant radial load that a group of bearings can endure for a basic rating life of 1 million revolutions. It is provided by bearing manufacturers and depends on bearing geometry, material quality, and manufacturing.
What is the equivalent dynamic load P?
The equivalent dynamic load P is the hypothetical constant radial load that would produce the same bearing life as the actual combination of radial and axial loads. For radial bearings: P = XF_r + YF_a, where X and Y are bearing-specific factors.
What is the life exponent p?
The life exponent p reflects the relationship between load and fatigue life. For ball bearings (point contact), p = 3. For roller bearings (line contact), p = 10/3 ≈ 3.33. The higher exponent for roller bearings indicates greater sensitivity to load changes.
What is the adjusted rating life L_na?
The adjusted rating life L_na accounts for reliability, material, lubrication, and contamination factors: L_na = a₁·a₂·a₃·L₁₀, where a₁ is the reliability factor, a₂ is the material factor, and a₃ is the operating condition factor.
What is the reliability factor a₁?
The reliability factor a₁ adjusts the L₁₀ life for higher reliability requirements. For 90% reliability, a₁ = 1.0. For 95%: 0.62. For 96%: 0.53. For 97%: 0.44. For 98%: 0.33. For 99%: 0.21. Higher reliability reduces the predicted life.
What is the static load rating C₀?
The static load rating C₀ (basic static load rating) is the maximum load a bearing can withstand without permanent deformation exceeding 0.0001 times the rolling element diameter. It is critical for applications with shock loads, vibration, or stationary bearings under load.
What is the static safety factor?
The static safety factor s₀ = C₀/P₀, where C₀ is the static load rating and P₀ is the equivalent static load. Recommended values: 1.0-1.5 for normal operation, 1.5-2.5 for moderate shock loads, 2.5-4.0 for heavy shock loads and high-reliability applications.
How does speed affect bearing life?
Speed affects life in hours: higher speed reduces hours for the same number of revolutions. The relationship is L₁₀h = L₁₀/(60·N). Speed also affects lubrication requirements — higher speeds require lower viscosity oils or specialized lubrication methods.
What is the difference between ball and roller bearing life?
Ball bearings use point contact (p=3), while roller bearings use line contact (p=10/3). For the same load ratio C/P, ball bearings have longer life at low loads, but roller bearings handle higher absolute loads. The different exponents reflect different fatigue mechanisms.
What is the ISO 281 standard?
ISO 281 is the international standard that specifies methods for calculating the dynamic load ratings and rating life of rolling bearings. It defines the L₁₀ life calculation and adjustment factors for reliability, material, and operating conditions.
How does lubrication affect bearing life?
Lubrication affects bearing life through the a₃ operating condition factor. Adequate lubrication (proper viscosity, cleanliness, and quantity) ensures a₃ = 1.0. Poor lubrication (low viscosity, contamination, insufficient quantity) reduces a₃ to 0.1-0.5, drastically reducing bearing life.
What is the effect of contamination on bearing life?
Contamination particles in the lubricant cause indentations in raceways, creating stress concentrations that initiate fatigue spalling. The contamination factor e_c ranges from 1.0 (clean) to 0.1 (heavy contamination). Clean assembly and sealed bearings significantly extend life.
What is the material factor a₂?
The material factor a₂ accounts for bearing steel quality and heat treatment. Standard bearing steel (through-hardened 52100) has a₂ = 1.0. Vacuum-degassed steel (improved purity) has a₂ = 1.1-1.2. Special bearing steels for high-temperature can have a₂ below 1.0.
How does temperature affect bearing life?
Temperature affects: lubricant viscosity (thinner at high temperature reduces film thickness), material hardness (above 150°C, hardness decreases), and internal clearance (thermal expansion changes fit). High-temperature bearings require stabilized dimensions and special lubricants.
What is the viscosity ratio κ?
The viscosity ratio κ = ν/ν₁ is the ratio of actual kinematic viscosity to the required viscosity for adequate lubrication. Values of κ > 2 indicate excellent lubrication, 1-2 good, 0.4-1 adequate, and <0.4 poor. ISO 281 uses κ to determine the operating condition factor a₃.
What is the fatigue life limit?
The fatigue life limit is the load below which bearing fatigue life is theoretically infinite. For rolling bearings, this is approximately C₀/20 for ball bearings and C₀/15 for roller bearings. Below this limit, subsurface fatigue does not initiate under ideal conditions.
What is the median life L₅₀?
L₅₀ (median life) is the life that 50% of bearings will reach or exceed. For rolling bearings, L₅₀ is approximately 5 times L₁₀. This relationship is based on the Weibull distribution of bearing fatigue life with a typical Weibull slope of 1.5 for bearings.
How do I select bearing reliability?
Reliability selection depends on application criticality: 90% (standard industrial), 95% (pumps, fans), 96-97% (gearboxes, compressors), 98% (critical process equipment), 99% (aerospace, medical). Higher reliability requires larger bearings or lower loads.
What is the L₁₀h life formula?
L₁₀h = (C/P)^p × 10⁶/(60·N) hours. For ball bearings (p=3): L₁₀h = 16667/N × (C/P)³. For roller bearings (p=10/3): L₁₀h = 16667/N × (C/P)^(10/3). This gives life in operating hours.
How do I calculate bearing life for variable loads?
For variable loads and speeds, use the equivalent load concept: P_eq = (Σ(P_i^p·N_i·t_i)/Σ(N_i·t_i))^(1/p), where P_i is the load, N_i speed, and t_i time at each condition. This provides a weighted average load for life calculation.
What is the difference between dynamic and static load?
Dynamic load is applied while the bearing rotates, causing cyclic stress and fatigue. Static load is applied while stationary or rotating very slowly, causing permanent deformation. Dynamic load determines fatigue life; static load determines deformation limits.
What is the L₁₀ life for oscillating bearings?
For oscillating motion, use the equivalent number of revolutions: for oscillation angle α (degrees), one oscillation = 4α/360 revolutions. Then L₁₀_osc = L₁₀_rot × 360/(4α).
How does bearing size affect life?
Larger bearings have higher load ratings C, providing longer life for the same load. However, larger bearings also have higher centrifugal forces at speed and may require more lubrication. Size selection balances load capacity, speed capability, and space constraints.
What is the load-life relationship?
Bearing life is inversely proportional to load raised to the power p: L ∝ 1/P^p. For ball bearings (p=3): doubling the load reduces life by a factor of 8. For roller bearings (p=10/3): doubling the load reduces life by a factor of approximately 10.
What bearing life is typical for different applications?
Typical L₁₀h requirements: household appliances 500-2000h, electric motors 10000-30000h, pumps 20000-50000h, gearboxes 10000-50000h, machine tools 20000-40000h, wind turbines 100000-200000h, aerospace 50000-100000h.
What is the Weibull distribution in bearing life?
Bearing fatigue life follows a Weibull distribution with shape parameter (slope) typically 1.1-1.5 for rolling bearings. This means the failure rate increases with time (wear-out region). The Weibull distribution is used to predict failure probability at any given life.
How do I account for misalignment in life calculation?
Misalignment increases edge loading, reducing effective bearing life. The effect depends on the angle and bearing type. For angular misalignment >0.1°, life reduction factors of 0.5-0.8 are common. Self-aligning bearings (spherical roller) accommodate misalignment up to 1-2°.
What is the system life for multiple bearings?
For a system with multiple bearings, the system life is lower than any individual bearing life. For n bearings: 1/L_sys^(1/e) = Σ(1/L_i^(1/e)), where e = 1.5 (Weibull slope). For two identical bearings: L_sys = L_i/2^(e) ≈ L_i/2.38.
How does housing fit affect bearing life?
Housing fit affects bearing internal clearance and load distribution. Too tight a fit reduces radial clearance, increasing preload and reducing life. Too loose a fit allows creep (rotation of the outer ring in the housing), causing fretting and wear.
What is the L₁₀ life for thrust bearings?
Thrust bearings use the same L₁₀ formula but with axial load ratings C_a instead of radial C_r. For thrust ball bearings: L₁₀ = (C_a/F_a)³ × 10⁶. For thrust roller bearings: L₁₀ = (C_a/F_a)^(10/3) × 10⁶.
What is the bearing adjustment factor a₁₂₃?
The combined adjustment factor a₁₂₃ = a₁·a₂·a₃ combines reliability, material, and operating condition adjustments. The adjusted rating life L_na = a₁₂₃·L₁₀. Modern standards (ISO 281:2007) use a more sophisticated system life approach.
Can I use this calculator for all bearing types?
This calculator supports ball bearings (p=3) and roller bearings (p=10/3) with dynamic load rating C and equivalent load P. For specialized bearings (needle, spherical, thrust), use type-specific life formulas and manufacturer data for C and X/Y factors.
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Glossary

Technical terms used in mortgage calculations explained in plain language.

Basic Rating Life (L₁₀)
The life in revolutions or hours that 90% of a group of identical bearings will reach or exceed under the same operating conditions.
Dynamic Load Rating (C)
The constant radial load a bearing can endure for a basic rating life of 1 million revolutions, supplied by the manufacturer catalogue.
Equivalent Dynamic Load (P)
A hypothetical constant radial load producing the same life as the actual combination of radial and axial loads (P = XF_r + YF_a).
Life Exponent (p)
The exponent in the life equation: p = 3 for ball bearings, p = 10/3 for roller bearings.
Reliability Factor (a₁)
Factor reducing the L₁₀ life for reliabilities above 90%. a₁ = 1.0 at 90%, 0.62 at 95%, 0.21 at 99%.
Adjusted Rating Life (L_na)
L_na = a₁·a₂·a₃·L₁₀, where a₂ covers material and a₃ covers lubrication/contamination/operating condition.
Static Load Rating (C₀)
The maximum load a stationary bearing can carry without permanent deformation exceeding 0.0001 times the rolling element diameter.
Static Safety Factor (s₀)
s₀ = C₀/P₀. Recommended 1.0–1.5 for normal duty, 1.5–2.5 for moderate shock, 2.5–4.0 for heavy shock.
Viscosity Ratio (κ)
κ = ν/ν₁, the ratio of actual to required kinematic viscosity. κ > 1 indicates adequate film lubrication per ISO 281.
Weibull Distribution
The statistical distribution governing bearing fatigue failure; typical bearing slope (shape parameter) is 1.1–1.5.
L₅₀ (Median Life)
The life that 50% of bearings reach or exceed; approximately 5 × L₁₀ for rolling bearings.
dn Value
Product of bore diameter (mm) and rotational speed (rpm); a screening metric for lubrication and speed limitations.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

ISO 281ANSI/ABMA 9SKF

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Page Information

Last Updated:

August 2026

Version:

2.1.0

License:

Free to use for educational and professional purposes.