Bearing Life (L10)
Compute rated bearing life L10 (10⁶ rev) and L10h (hours). Optional reliability a₁ and ISO 281 combined factor a_iso give modified life Lnm.
Inputs
Formula
L10 = (C/P)^p; L10h = 10⁶/(60n)·L10; Lnm = a1·aiso·L10h (p=3 ball / 10/3 roller)
Use p=3 for ball bearings, p=10/3 for roller bearings.
How to use
- Fill in Basic dynamic load C, Equivalent load P, Speed n, Life exponent p, Reliability a₁, ISO factor a_iso in the Inputs section (watch the unit on each field).
- Click Calculate; the tool evaluates the formula shown above.
- Read Basic life L10, Life L10h, Modified life Lnm in the results area.
Formula notesRated life L10 = (C/P)^p · 10⁶ rev; ball p=3, roller p=10/3. C = dynamic load rating, P = equivalent load.
Formula · Worked Example · Knowledge
Formula
Rated life $L_{10}$ is the total revolutions (or hours at a given speed) before 90% of a batch of identical bearings suffer fatigue spalling:
$$L_{10}=\left(\frac{C}{P}\right)^{p}\cdot 10^{6}\ \text{rev}$$
$C$ = dynamic load rating (N), $P$ = equivalent dynamic load (N); ball bearing $p=3$, roller bearing $p=10/3$. In hours:
$$L_{10h}=\frac{10^{6}}{60\,n}\left(\frac{C}{P}\right)^{p}\ (\text{h})$$
ISO 281 adds reliability factor $a_1$ and condition factor $a_{ISO}$ for lubrication/contamination.
$$L_{10}=\left(\frac{C}{P}\right)^{p}\cdot 10^{6}\ \text{rev}$$
$C$ = dynamic load rating (N), $P$ = equivalent dynamic load (N); ball bearing $p=3$, roller bearing $p=10/3$. In hours:
$$L_{10h}=\frac{10^{6}}{60\,n}\left(\frac{C}{P}\right)^{p}\ (\text{h})$$
ISO 281 adds reliability factor $a_1$ and condition factor $a_{ISO}$ for lubrication/contamination.
Worked Example
Deep-groove ball bearing 6206, radial load $P=2000\ \text{N}$, speed $n=800\ \text{r/min}$, dynamic rating $C=19500\ \text{N}$ ($p=3$). Find rated life in hours.
Step 1 — life in revolutions:
$$L_{10}=\left(\frac{19500}{2000}\right)^{3}\cdot10^{6}\approx 9.27\times10^{8}$$
Step 2 — life in hours:
$$L_{10h}=\frac{9.27\times10^{8}}{60\times800}\approx 19270\ \text{h}$$
Step 1 — life in revolutions:
$$L_{10}=\left(\frac{19500}{2000}\right)^{3}\cdot10^{6}\approx 9.27\times10^{8}$$
Step 2 — life in hours:
$$L_{10h}=\frac{9.27\times10^{8}}{60\times800}\approx 19270\ \text{h}$$
Key Points
- $L_{10}$ is the 90%-reliability rated life; multiply by $a_1$ for higher reliability (e.g. 0.62 at 95%).
- Equivalent load $P$ lumps axial and radial loads into an effective radial load per the duty.
- Good lubrication / clean conditions give $a_{ISO}>1$; severe contamination can drop it to 0.1.