What does L10 bearing life mean?

It is the life reached or exceeded by 90% of a population of identical bearings under identical conditions. It is a statistical rating, not a minimum — one bearing in ten is expected to fail before reaching it.

What is the difference between ball and roller bearing life?

Only the life exponent. Ball bearings use p = 3, roller bearings p = 10/3. Because the exponent is larger for rollers, roller bearings are less sensitive to overload and gain more life from a given reduction in load.

Why does halving the load multiply the life by eight?

Because the life ratio is (C/P)³ for a ball bearing. Halving P doubles C/P, and 2³ = 8. This extreme sensitivity is why an accurate load estimate matters so much — a 25% error in load changes predicted life by a factor of two.

Should I use L10 or a higher reliability figure?

Use L10 for general machinery. For applications where failure is costly or dangerous — aerospace, medical, remote installations — use L5 or L1, which are substantially shorter. The adjustment factors come from the bearing manufacturer's catalogue.

What is the equivalent dynamic load P?

A single load that would give the same life as the actual combined radial and axial loads. It is computed from the radial and axial components with factors that depend on the bearing type and the ratio of axial to radial load — take it from the manufacturer's catalogue rather than estimating.

Bearing Life Calculator

Basic rating life L10 for a ball or roller bearing from its dynamic load rating and the applied equivalent load, in revolutions and in hours.

Data verified 2026-09-29 · based on n/a — standard engineering relationships, no single governing revision

Quick Answer

Basic rating life is L10 = (C ÷ P)^p × 10⁶ revolutions, with p = 3 for ball bearings and p = 10/3 for roller bearings. Halving the applied load multiplies the life by eight for a ball bearing — the exponent is the whole story.

Bearing L10 Rating Life

Dynamic load rating, C (lb)

Equivalent dynamic load, P (lb)

Speed (RPM)

Life exponent, p (3 ball / 3.333 roller)

The Formulas Used

Basic rating life: L10 = (C ÷ P)^p × 10⁶ revolutions
In hours: L10h = L10 ÷ (60 · n)
Life exponent p: 3 for ball bearings, 10/3 for roller bearings

What L10 Actually Means

L10 is the life that 90% of a population of apparently identical bearings will reach or exceed under identical conditions. It is not a minimum life and not a guarantee — one bearing in ten is expected to fail before it. That is why critical applications use higher reliability adjustments, and why a gearbox designed to L10 may still see an early failure.

The modern standard uses the term basic rating life and extends it with a life modification factor a_ISO that accounts for lubrication, contamination and fatigue load limit. A well-lubricated, clean bearing can achieve several times its basic rating; a starved or contaminated one can achieve a small fraction of it. The basic rating assumes good conditions and is the starting point, not the answer.

Frequently Asked Questions

What does L10 bearing life mean?: It is the life reached or exceeded by 90% of a population of identical bearings under identical conditions. It is a statistical rating, not a minimum — one bearing in ten is expected to fail before reaching it.
What is the difference between ball and roller bearing life?: Only the life exponent. Ball bearings use p = 3, roller bearings p = 10/3. Because the exponent is larger for rollers, roller bearings are less sensitive to overload and gain more life from a given reduction in load.
Why does halving the load multiply the life by eight?: Because the life ratio is (C/P)³ for a ball bearing. Halving P doubles C/P, and 2³ = 8. This extreme sensitivity is why an accurate load estimate matters so much — a 25% error in load changes predicted life by a factor of two.
Should I use L10 or a higher reliability figure?: Use L10 for general machinery. For applications where failure is costly or dangerous — aerospace, medical, remote installations — use L5 or L1, which are substantially shorter. The adjustment factors come from the bearing manufacturer's catalogue.
What is the equivalent dynamic load P?: A single load that would give the same life as the actual combined radial and axial loads. It is computed from the radial and axial components with factors that depend on the bearing type and the ratio of axial to radial load — take it from the manufacturer's catalogue rather than estimating.

Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

#	Source	Type	Revision / method
[1]	ASME B1.1 — Unified Inch Screw Threads	standard	ASME B1.1-2019 — source
[2]	ASTM A615 — Deformed steel bars for concrete reinforcement	standard	ASTM A615/A615M-20 — source
[3]	ASTM E140 — Hardness Conversion Tables	standard	ASTM E140-12b — source
[4]	Values computed in your browser	derived	Evaluated locally from the formulas shown on the page. No data leaves the device.
[5]	ISO 4287 — Surface texture: Profile method	standard	ISO 4287:1997 — source
[6]	ISO 68-1 — Basic profile	standard	ISO 68-1:2023 — source
[7]	NFPA 70 NEC Table 310.16	standard	NEC 2023 (NFPA 70-2023) — source

Data Sources

Standard	Revision	What it covers on this page
Formulas as shown on this page	n/a — standard engineering relationships, no single governing revision	every value this calculator produces

Cross-checked against:

Formulas verified against the corresponding reference chart on this site, so the calculator and the published tables agree

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
All outputs	Computed in the browser from the formulas above. No data leaves the device.

Outputs are computed from the formulas shown. Verify against the governing standard for design or acceptance work.

Accuracy and use. The values on this page are compiled from the published standards and cross-checked sources listed above. Where values are derived, the derivation is stated. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Every value on this page is traceable to the sources listed above. If you use the data in a document, paper or report, cite it as:

Plain text

Engineering Reference. "Bearing Life Calculator." https://refmanual.com/calculators/bearing-life/ (accessed 2026-09-29). Data from Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision.

BibTeX

@misc{bearing-life,
  title        = {Bearing Life Calculator},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/calculators/bearing-life/}},
  note         = {Accessed: 2026-09-29},
  source       = {Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Bearing Life Calculator
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/calculators/bearing-life/
PY  - 2026
DA  - 2026-09-29
N1  - Source: Formulas as shown on this page, n/a — standard engineering relationships, no single governing revision
ER  -

Each row in the tables above also has a permanent link — hover a row and use the # link to cite a single value rather than the whole page.