Bearing Life Calculator
The L10 fatigue clock: rating life from the catalogue's C over your load, converted to hours at speed — with the load-halving leverage priced.
Bearing Life Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Basic rating life; no a_ISO lubrication correction
- Constant radial load at steady speed
In short: A ball bearing rated C = 30 kN carrying P = 5 kN at 1,500 rpm owns an L10 life of 216.000000 million revolutions — (30 ÷ 5)³ — which at speed converts to 2,400.000000 hours: 100 days of continuous running before fatigue claims ten percent of an identical population. The cubic law is the design lesson: halve the load and the life multiplies by eight, which is why bearing selection is the art of buying revolutions with diameter.
Formula
L₁₀ = (C/P)ᵏ ··· L₁₀ₕ = L₁₀ × 10⁶/(60n) · k = 3 ball, 10/3 roller
Fatigue is a statistics problem wearing a catalogue number: C is the load a bearing population survives a million revolutions with, and life scales with the load ratio to the third (ball) or ten-thirds (roller) power. L10 names the honest contract — ninety percent of identical bearings reach it; it is a median's pessimistic sibling, not a warranty.
Worked Example
- Pick ball or roller — the exponent is the type.
- Enter the catalogue C and your equivalent load P.
- Enter the working speed.
- Read the life in revolutions and in hours.
Defaults: C 30, P 5, ball, 1,500 rpm → 216.000000 M rev, 2,400.000000 h. The roller check: k = 10/3 → 392.498048... M rev — line contact endures more. The leverage check: P 2.5 → 19,200 h, exactly ₈× — load is the whole negotiation.
Strengths & Limits Of This Model
Where this engine is strong
- Hours and revolutions side by side
- Load-halving leverage computed
Where it stops
- No combined-load X/Y algebra
- No reliability adjustment above 90%
Practical Use Cases
Bearing selection
catalogue C vs real load
Maintenance planning
replacement intervals
Teaching
statistics under load
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Bearing Life Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What does the '10' in L10 actually mean?
That ten percent of an identical bearing population is expected to have fatigued by the time the rating life completes — L10 is the ninety-percent-reliability contract. A single bearing may outlast it by multiples or quit early; the statistic only means something across a fleet or across years of fleet experience. Engineering with bearings is engineering with populations.
Why is the exponent 3 for ball and 10/3 for roller?
Because contact geometry sets the fatigue mechanics: balls touch steel at a point, rollers along a line, and the line spreads the stress so life falls more slowly with load. ISO 281 compresses that physics into the exponents 3 and 10/3. The practical read: rollers are the heavier haulers — the same 6:1 rating-to-load ratio buys a roller 392.498048 million revolutions where a ball buys 216.
How do I get P from radial and axial loads?
Catalogues define an equivalent load P = X·Fr + Y·Fa with factor tables per bearing series — and for pure radial duty P is simply Fr. This page takes P as given so the life arithmetic stays visible; the equivalent-load algebra is the catalogue's job. Enter the honest combined number and the exponent does the rest.
Why did my hours come out small despite a big C?
Because speed divides: life in revolutions is fixed by C/P, but every revolution costs one sixtieth of a minute, so a fast shaft burns its revolutions quickly. Doubling speed halves hours without touching the bearing. The revolutions card and the hours card sit side by side because designs optimise one or the other and confusing them is the classic selection error.
What is a good L10 target for machine design?
Traditional targets: indefinite or 30,000–40,000 hours for machines running eight hours a day, 100,000+ for 24-hour duty, shorter for vehicles that coast between duties. The right question is what the machine serves — a 2,400-hour rating suits a seasonal tool and dooms a server fan. Life targets are application policy, not bearing property.
Does lubrication change any of this?
Not the L10 arithmetic — but it changes whether reality honours it. Modern standards add a viscosity-ratio and contamination correction that can multiply the basic life up or grind it down below the rating; a starved bearing never reads the formula. Treat L10 as the clean-room baseline and grease as the enforcement mechanism.
Why does halving the load multiply life by eight?
Because the cubic law compounds: life goes as the load ratio cubed, so a factor of one half on load becomes two-cubed on life. It is the strongest leverage in rotating design — a slightly larger bearing or a slightly gentler duty buys geological time. The leverage card computes 2ᵏ for your bearing type so the lesson is priced, not recited.
Is a bearing that survives L10 worn out?
No — L10 is the fatigue floor, not a death date: half the population outlives it, often by far. Wear-out modes (grease depletion, contamination, corrosion) usually set practical service life long before rolling-element fatigue does. The rating tells you when to START listening for fatigue; the maintenance schedule listens for everything else.