Q: Does this calculator support SI and imperial units?

Yes. Switch between SI (loads in newtons, N) and imperial (loads in pounds-force, lbf) at the top; 1 lbf = 4.4482216 N. Speed is always entered in rev/min because the factor 60 in L10h = (10^6/(60·n))·(C/P)^p requires rev/min. All internal math is done in SI and converted at input and output. Life is reported in hours and in days (L10h/24).

Q: Is this an ISO 281 bearing rating I can use for final selection?

It implements the ISO 281:2007 basic and modified rating life equations and the single-row deep groove ball bearing X/Y/e table, and reproduces a manufacturer-style simple case (C=10000 N, P=2000 N, n=1000 rev/min → L10=125×10^6 rev, L10h=2083 h) and the Shigley combined-load example (Fr=5 kN, Fa=2 kN → P=5.34 kN). It is for preliminary sizing and study. L10 assumes constant load and speed and the catalogue C and C0 of the actual bearing. Final selection and life must be verified by a qualified engineer against the manufacturer's data and ISO 281.

Question 1

What is L10 bearing life and how is it calculated?

Accepted Answer

L10 is the basic rating life from ISO 281 — the life in millions of revolutions reached or exceeded by 90% of a large group of apparently identical bearings (10% are expected to fail earlier). It is computed as L10 = (C/P)^p, where C is the basic dynamic load rating from the catalogue, P is the equivalent dynamic bearing load, and p is the life exponent: p = 3 for ball bearings and p = 10/3 (≈3.333) for roller bearings. Life in hours is L10h = (10^6/(60·n))·(C/P)^p with the speed n in rev/min.

Question 2

How do I find the equivalent dynamic load P from radial and axial loads?

Accepted Answer

For a single-row deep groove ball bearing, compare the ratio Fa/(V·Fr) with the limiting ratio e. If Fa/(V·Fr) ≤ e the axial load is small and P = Fr (X=1, Y=0). If Fa/(V·Fr) > e then P = X·V·Fr + Y·Fa with X = 0.56, and Y and e read from the standard X/Y/e table as a function of f0·Fa/C0 (interpolated). V is the rotation factor: 1.0 when the inner ring rotates, 1.2 when the outer ring rotates. This X/Y/e table is only valid for single-row deep groove ball bearings.

Question 3

What are the reliability factor a1 and the modified life Lnm?

Accepted Answer

The basic life L10 corresponds to 90% reliability, where a1 = 1.0. For higher reliability the modified rating life is Lnm = a1·aISO·L10, where a1 < 1 from ISO 281 Table 1 (for example a1 = 0.64 at 95%, 0.25 at 99%). Higher reliability therefore gives a SHORTER predicted life, not a longer one. aISO is the life-modification factor for lubrication, contamination and the fatigue load limit; full aISO requires ISO/TR 1281-2 inputs, so this tool keeps aISO as a user input defaulting to 1.0 rather than auto-computing it.

Question 4

Does this calculator support SI and imperial units?

Accepted Answer

Yes. Switch between SI (loads in newtons, N) and imperial (loads in pounds-force, lbf) at the top; 1 lbf = 4.4482216 N. Speed is always entered in rev/min because the factor 60 in L10h = (10^6/(60·n))·(C/P)^p requires rev/min. All internal math is done in SI and converted at input and output. Life is reported in hours and in days (L10h/24).

Question 5

Is this an ISO 281 bearing rating I can use for final selection?

Accepted Answer

It implements the ISO 281:2007 basic and modified rating life equations and the single-row deep groove ball bearing X/Y/e table, and reproduces a manufacturer-style simple case (C=10000 N, P=2000 N, n=1000 rev/min → L10=125×10^6 rev, L10h=2083 h) and the Shigley combined-load example (Fr=5 kN, Fa=2 kN → P=5.34 kN). It is for preliminary sizing and study. L10 assumes constant load and speed and the catalogue C and C0 of the actual bearing. Final selection and life must be verified by a qualified engineer against the manufacturer's data and ISO 281.

Rolling Bearing LifeCalculator — ISO 281 L10

Rolling Bearing Life
Calculator — ISO 281 L10