Bearing Life Calculator
Calculate L10 rolling-bearing rating life, adjust for reliability, combine catalog load factors, or reverse-solve the required dynamic load rating.
Calculator is for informational purposes only. Terms and Conditions
Equation and method
The displayed relationship updates with the selected solve mode.
This calculator evaluates basic rolling-bearing fatigue rating life. It does not model wear, corrosion, electrical erosion, lubrication, contamination, misalignment, mounting, or thermal limits.
Choose the bearing calculation
Choose what to solve, the rolling-element family, and how the equivalent load will be entered.
Enter the known values
Use the dynamic load rating C, not the static rating C0. Values update automatically.
Enter manufacturer rating data and the equivalent dynamic load for the operating condition. For combined load mode, enter X and Y from the exact bearing catalog.
Result
Rating-life result first, followed by useful checks and warnings.
Result details
- Check—
Show calculation stepsReview conversions, formula, substitution, reliability adjustment, and reverse check
- Enter valid values to see the complete calculation.
Load sensitivity
Compare calculated rating life at 80%, 100%, and 120% of the active equivalent load to see how strongly load changes fatigue life.
- Enter valid values to populate the chart.
Method, Sources, and Assumptions
Calculation basis, scope, constants, and final verification requirements.
Uses the ISO 281 basic rating-life relationship with published reliability factors. Manufacturer-specific X and Y load factors remain user inputs.
- C and P must correspond to the same force basis and the selected operating condition.
- L10 is a statistical fatigue rating life, not a guaranteed service-life prediction for an individual bearing.
- Final selection must verify bearing-specific load factors, speed limits, lubrication, fits, mounting, contamination, temperature, and manufacturer requirements.
Calculator guide
Understanding Your Bearing Life Result
The Bearing Life Calculator determines rolling-bearing fatigue rating life from the basic dynamic load rating C, equivalent dynamic load P, bearing family, and rotational speed. It can also reverse the same relationship to determine the theoretical dynamic rating C required for a target life or the allowable equivalent load P for a selected bearing.
The primary life result is statistical, not an expiration time. At the default 90% reliability setting, the calculator reports L10: the basic rating life associated with 90% reliability under the ISO 281 basic rating-life framework. A real bearing can fail sooner because of lubrication, contamination, mounting, fit, clearance, alignment, temperature, electrical erosion, shock, or other conditions that the basic equation does not determine.
- Primary output
- L10 or the selected reliability-adjusted rating life in hours, with life in revolutions shown as a supporting result.
- Core relationship
- Life varies with the power of the ratio C/P, so relatively small load changes can produce large life changes.
- Critical input check
- Use basic dynamic load rating C, not static load rating C0, and use the correct equivalent dynamic load P.
How to Use the Bearing Life Calculator
Start with the calculation you actually need, then enter manufacturer and application data in compatible units. The calculator automatically updates valid results and preserves the physical quantity when you change supported units.
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Choose what to solve
Select Bearing life to predict rating life, Required dynamic rating C to size the theoretical catalog rating needed for a target life, or Allowable equivalent load P to determine the theoretical constant equivalent load corresponding to a selected C and target life.
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Select ball or roller bearing behavior
The calculator uses a life exponent of 3 for ball bearings and 10/3 for roller bearings. This choice changes the mathematical sensitivity of life to the C/P ratio.
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Enter P directly or build it from radial and axial load
If you already have the equivalent dynamic bearing load, enter P. If you use the combined-load option, enter Fr, Fa, X, and Y only when the factors and applicable load rule come from the exact bearing manufacturer’s data. The calculator does not guess catalog factors.
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Enter speed and select reliability when needed
Speed is required because revolutions must be converted to operating hours. The advanced reliability setting changes the life designation and applies the calculator’s published reliability factor a1; it is not a lubrication, contamination, or general service factor.
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Check the result before selecting hardware
Review the life in hours, life in revolutions, C/P ratio, warnings, and calculation steps. For reverse sizing, select a real bearing whose manufacturer rating satisfies the calculated requirement only after the rest of the application checks are completed.
Bearing Life Inputs and Outputs
The accuracy of a bearing-life calculation is controlled less by arithmetic than by whether C and P represent the correct bearing and operating condition. Keep force units physically consistent; the calculator handles supported N, kN, lbf, and kip conversions internally.
- Dynamic load rating C
- The bearing’s basic dynamic load rating from the exact manufacturer catalog or product data. Under the standardized rating definition, C is associated with a basic rating life of one million revolutions under the stated rating conditions. It is not the maximum permissible operating load, breaking strength, or static rating C0.
- Equivalent dynamic load P
- A constant equivalent bearing load representing the fatigue effect of the actual load condition. For a combined-load calculation, the calculator can evaluate P = XFr + YFa when X and Y are supplied by the user and that relationship is applicable to the bearing.
- Radial load Fr and axial load Fa
- Forces perpendicular to and along the bearing axis, respectively. These should be bearing reactions for the operating condition being evaluated, not automatically the external machine force applied somewhere else on the shaft.
- Load factors X and Y
- Dimensionless manufacturer factors used to form an equivalent dynamic load for the applicable bearing and load condition. Their values can depend on bearing design and catalog rules, so they should not be transferred casually between bearing series or load cases.
- Catalog threshold e
- Many bearing catalogs compare the ratio Fa/Fr with a bearing-specific limiting value e. That comparison may determine whether axial load changes the equivalent-load equation and which X/Y factors apply. The calculator does not assume a universal e value.
- Rotational speed n
- Bearing speed used to convert a fatigue life in revolutions to operating hours. The calculator accepts rpm or revolutions per second and computes from a canonical speed state.
- Reliability and a1
- The default 90% setting corresponds to L10 and a1 = 1. Higher selected reliability reduces the reported rating life using the reliability factor built into the calculator.
- Required dynamic rating C
- The minimum theoretical basic dynamic load rating produced by rearranging the rating-life equation for the entered target life. A catalog bearing must still be checked for static capacity, speed, lubrication, fit, clearance, and the rest of the application.
- Allowable equivalent load P
- The theoretical constant equivalent dynamic load corresponding to the entered C, speed, target life, bearing family, and reliability. It is not a universal maximum bearing load or a complete design limit.
Bearing Life Formula and Calculation Method
The calculator uses the basic rolling-bearing rating-life relationship. The core life calculation is a closed-form equation: calculate the C/P ratio, raise it to the bearing-family exponent, then convert revolutions to hours at the entered speed. Reliability adjustment is applied with a1.
Basic L10 rating life
Plain language: basic L10 life in millions of revolutions equals the dynamic rating divided by equivalent dynamic load, raised to the bearing life exponent.
Use C and P in the same physical force units. Their ratio is dimensionless. For example, 30 kN / 5 kN and the same physical loads expressed in lbf both produce C/P = 6 and therefore the same calculated life.
Convert rating life to operating hours
Plain language: multiply the life in millions of revolutions by one million, then divide by revolutions per hour.
Reliability adjustment
Plain language: the selected reliability factor a1 scales the basic L10 rating life. The calculator then reports the corresponding designation such as L5 for 95% reliability or L1 for 99% reliability.
Equivalent dynamic load for combined loading
Plain language: the calculator combines radial and axial bearing loads using user-entered radial and axial load factors.
Do not assume this equation must always be used simply because both Fr and Fa exist. Manufacturer tables may specify P = Fr in one load-ratio range and a different X/Y relationship in another. Use the exact product catalog rule, including any Fa/Fr threshold based on e.
Required dynamic load rating
Use this rearrangement when equivalent load, speed, target life, bearing family, and reliability are known and the required basic dynamic load rating is the unknown.
Allowable equivalent dynamic load
Use this rearrangement to find the theoretical constant equivalent load corresponding to the selected C and target rating life.
- \(L_{10}\)
- Basic rating life at 90% reliability, expressed in millions of revolutions.
- \(L_{10h}\)
- Basic L10 rating life converted to operating hours at constant speed.
- \(L_{\mathrm{selected}}\)
- Rating life after applying the selected reliability factor a1.
- \(L_{\mathrm{target}}\)
- Target operating life used in the calculator’s reverse-sizing modes.
- \(C\)
- Basic dynamic load rating from the bearing manufacturer.
- \(P\)
- Equivalent dynamic bearing load.
- \(p\)
- Life exponent: 3 for ball bearings and 10/3 for roller bearings.
- \(n\)
- Rotational speed in revolutions per minute in the hour-conversion equation.
- \(a_1\)
- Life adjustment factor for the selected reliability.
- \(F_r\)
- Radial bearing load.
- \(F_a\)
- Axial bearing load.
- \(X\)
- Catalog radial load factor for the applicable bearing and load condition.
- \(Y\)
- Catalog axial load factor for the applicable bearing and load condition.
| Setting | Designation or value | Factor used |
|---|---|---|
| Ball bearing | Life exponent | p = 3 |
| Roller bearing | Life exponent | p = 10/3 |
| 90% reliability | L10 | a1 = 1.00 |
| 95% reliability | L5 | a1 = 0.64 |
| 96% reliability | L4 | a1 = 0.55 |
| 97% reliability | L3 | a1 = 0.47 |
| 98% reliability | L2 | a1 = 0.37 |
| 99% reliability | L1 | a1 = 0.25 |
Worked Bearing Life Example
Consider a ball bearing with a basic dynamic load rating of 30 kN, an equivalent dynamic load of 5 kN, and a constant speed of 1,500 rpm. Calculate its basic L10 rating life at the calculator’s default 90% reliability.
Calculate life in revolutions
Because L10 is expressed in millions of revolutions, the result is 216 million revolutions.
Convert revolutions to operating hours
Result
L10 = 216 million revolutions = 2,400 operating hours
Under the entered constant equivalent load and speed, the candidate has a basic 90%-reliability fatigue rating life of 2,400 hours. That result must still be compared with the required machine life and the bearing’s other application limits.
How to Interpret Bearing Life Results
A bearing-life result is useful only after it is tied back to the machine duty, reliability target, and quality of the load model. The number describes calculated fatigue rating life under the entered conditions; it does not prove that the complete bearing arrangement is suitable.
What L10 means
L10 is the basic rating-life designation associated with 90% reliability. It is a population-based fatigue measure, so it should not be interpreted as the exact hour at which an individual bearing will fail.
Load sensitivity is severe
Holding C, speed, bearing type, and all other conditions constant, increasing P by 10% reduces basic calculated life to about 75.1% of its previous value for a ball bearing and about 72.8% for a roller bearing. This follows directly from the exponent in the C/P relationship.
Speed changes hours, not L10 revolutions
With C and P unchanged, the basic L10 revolution count is unchanged by rpm. Doubling speed simply accumulates those revolutions twice as fast, so the calculated life in operating hours is cut in half.
Use the C/P ratio as a reasonableness check
The C/P ratio is the quantity being raised to the life exponent. If P approaches C, predicted life becomes short. If P exceeds C, the calculator can still evaluate the equation, but the L10 result is below one million revolutions and the application deserves immediate review rather than a normal selection decision.
C/P is not a universal bearing safety factor. It is a useful ratio within the rating-life equation, not a standalone acceptance criterion for static capacity, shock loading, speed, lubrication, or the complete bearing system.
For reverse sizing, treat the result as a requirement—not a selected bearing
If the calculator reports a required C of 42 kN, that does not mean every bearing with C ≥ 42 kN is acceptable. It means the basic fatigue equation requires at least that theoretical dynamic rating for the entered P, speed, target life, bearing family, and reliability. Static capacity, speed, geometry, fit, clearance, lubrication, sealing, arrangement, and manufacturer limits remain separate checks.
Common Bearing Life Calculation Mistakes
Most serious bearing-life errors come from the wrong input model rather than from the exponent itself. Check the load definition and catalog data before trusting a highly precise numerical result.
Using C0 instead of C
The L10 fatigue equation uses the basic dynamic load rating C. Static rating C0 belongs to a different static-capacity check. Because catalog tables often show both values next to each other, this is an easy but consequential input mistake.
Using Fr when the calculation requires P
A radial reaction is not always the same as equivalent dynamic load. Axial load and bearing-specific catalog rules can change P. Use the manufacturer’s equivalent-load method for the exact bearing.
Adding Fr and Fa directly
The general combined-load form is P = XFr + YFa, not automatically Fr + Fa. Even that form must be used with the correct catalog factors and any applicable load-ratio threshold.
Guessing X, Y, or e
X, Y, and e are not universal constants for all ball or roller bearings. Values copied from a different bearing family, series, contact angle, or load condition can materially distort P and therefore calculated life.
Using the wrong life exponent
The calculator uses p = 3 for ball bearings and p = 10/3 for roller bearings. Selecting the wrong family changes the nonlinear relationship between load and calculated life.
Averaging variable loads arithmetically
A machine that spends most of its time lightly loaded and a short period heavily loaded cannot generally be represented by an arithmetic-average force. Fatigue damage is nonlinear with load, so high-load segments can consume a disproportionate share of life and should be weighted by the revolutions accumulated at each operating condition.
Treating higher reliability as a service factor
The calculator’s reliability a1 changes the statistical rating-life level. It does not represent lubrication quality, contamination, shock, misalignment, or any other operating-condition correction.
Turning L10 hours into an automatic replacement interval
L10 is a fatigue rating quantity. Maintenance intervals should also consider condition monitoring, failure consequences, lubricant life, environment, manufacturer guidance, and the machine’s maintenance strategy.
Rating Life vs. Real Bearing Service Life
The basic bearing-life equation is intentionally narrow: it predicts fatigue rating life from load capacity and equivalent load under the method’s assumptions. Real service life can be shorter when surface condition, lubrication, contamination, installation, temperature, electrical current, or load history becomes the controlling failure mechanism.
Constant-load simplification
The direct life mode represents a constant equivalent dynamic load P. If the machine cycles among different loads or speeds, break the duty into operating segments and use a defensible variable-load fatigue method rather than one arithmetic-average load.
Lubrication is not modeled by a1
The reliability factor in this calculator changes survival probability only. It does not calculate lubricant viscosity ratio, film condition, contamination effects, fatigue load limit, or a manufacturer-specific modified-life factor.
Static and shock capacity remain separate
A bearing can have a long calculated fatigue life and still be unacceptable under peak, impact, parked, oscillating, or very low-speed loads. Check the manufacturer’s equivalent static load method and C0 separately.
Speed suitability is more than hour conversion
The equation uses speed to convert revolutions to hours, but it does not prove that the bearing, cage, seals, and lubricant can operate at that rpm without excessive heat or lubrication problems.
Fits, clearance, and alignment can change internal loading
Interference fits, thermal expansion, shaft or housing deflection, preload, and misalignment can alter internal load distribution and operating clearance even when the external load calculation is correct.
Contamination and non-fatigue failure modes can dominate
Wear, corrosion, electrical erosion, lubricant breakdown, seal failure, mounting damage, and contamination are not converted into a guaranteed service-life prediction by the basic L10 equation.
When ISO 281 basic life is not enough
ISO 281 provides the basic dynamic load rating and rating-life framework used by this calculator. When lubrication, contamination, fatigue load limit, operating clearance, misalignment or tilting, internal rolling-element load distribution, or roller edge stress materially affects the analysis, a more detailed reference-life method may be appropriate.
ISO 16281:2025 addresses modified reference rating life for universally loaded rolling bearings and includes additional influences beyond the basic ISO 281 treatment. It is a deeper engineering method, not a replacement for verifying manufacturer-specific application limits or non-fatigue failure mechanisms.
Standards, Sources, and Calculation Basis
The calculator and this guide use the ISO 281 basic rating-life framework and authoritative bearing-manufacturer guidance for the basic life equation, equivalent dynamic load form, and reliability factors. The worked example was checked by forward calculation and by algebraically solving back to the original dynamic rating.
- ISO 281:2007 — Rolling bearings — Dynamic load ratings and rating life — ISO currently lists ISO 281:2007 as the published International Standard for dynamic load ratings and rating life. It was confirmed in 2021 and remains current while a replacement revision is under development.
- ISO 16281:2025 — Rolling bearings — Methods for calculating the modified reference rating life for universally loaded bearings — Provides a more detailed reference-life method that can account for influences such as internal load distribution, misalignment or tilting, operating clearance, lubrication, contamination, and fatigue load limit.
- SKF bearing life guidance — Supports the basic L10 relationship, p = 3 for ball bearings, p = 10/3 for roller bearings, conversion to operating hours, and the general equivalent dynamic load form P = XFr + YFa.
- JTEKT / Koyo bearing life and reliability guidance — Supports the basic dynamic load rating definition and reliability adjustment factors associated with 90% through 99% reliability.
The calculator intentionally requires user-supplied X and Y factors for combined loading rather than embedding a generic factor table. That keeps product-specific manufacturer rules separate from the universal basic-life relationship.
Bearing Life Calculator FAQ
These answers address common interpretation and input questions that remain after using the calculator.
What does L10 bearing life mean?
L10 is the basic rolling-bearing fatigue rating life associated with 90% reliability under the basic rating-life framework. It is a population-based rating quantity, not a guaranteed failure time for an individual bearing.
How do I calculate bearing life in hours?
First calculate basic life in millions of revolutions with \(L_{10}=(C/P)^p\). Then convert to hours with \(L_{10h}=10^6L_{10}/(60n)\), where n is speed in rpm. The calculator performs both steps automatically.
What is the difference between bearing ratings C and C0?
C is the basic dynamic load rating used in the fatigue-life equation. C0 is the basic static load rating used for a separate static-capacity or permanent-deformation check. Do not substitute C0 for C in the L10 equation.
What is equivalent dynamic bearing load P?
P is the constant equivalent load used in the rating-life equation to represent the fatigue effect of the actual loading condition. When radial and axial loads act together, the applicable manufacturer method can use factors such as X and Y to form P.
Can I calculate bearing life with radial and axial loads?
Yes, when the applicable equivalent-load relationship and manufacturer factors are known. The calculator’s combined-load mode accepts Fr, Fa, X, and Y and evaluates P = XFr + YFa. Verify whether that equation and those factors apply to the exact bearing and Fa/Fr range.
Where do I get X, Y, and e for a bearing?
Use the exact bearing manufacturer’s catalog or technical data for the selected bearing and load condition. X and Y can depend on bearing design and the relationship between Fa and Fr, while e is commonly used as a bearing-specific threshold in those catalog rules.
Why is p = 3 for ball bearings and 10/3 for roller bearings?
Those are the life exponents used by the basic rolling-bearing rating-life relationship for the two rolling-element families. Because the exponents differ, the same change in C/P produces a different calculated life response for ball and roller bearings.
Does higher rpm reduce L10 bearing life?
For the basic equation with C and P held constant, rpm does not change L10 measured in revolutions. Higher rpm reduces the same rating life when expressed in operating hours because the bearing accumulates revolutions faster. Actual high-speed suitability still requires separate manufacturer checks.
What dynamic load rating C do I need for a target bearing life?
Use the calculator’s Required dynamic rating C mode. Enter the equivalent dynamic load, speed, target life, bearing family, and reliability. The result is the minimum theoretical basic dynamic load rating required by the rating-life equation, not a complete bearing selection.
Can I use the calculated L10 hours as a replacement interval?
Not automatically. L10 is a statistical fatigue rating quantity. A maintenance or replacement interval should also consider actual duty, lubricant life, contamination, condition monitoring, failure consequences, maintenance strategy, and manufacturer recommendations.
Can a bearing fail before its calculated L10 life?
Yes. L10 is statistical and addresses fatigue rating life under a defined model. Lubrication failure, contamination, corrosion, electrical erosion, improper fits or clearance, mounting damage, misalignment, shock, seal problems, or other failure modes can shorten actual service life.