Bearing Life Calculator Formula
Understand the math behind the bearing life calculator. Each variable explained with a worked example.
Formulas Used
L10 Life (revolutions)
l10_rev = pow(dynamic_cap / equiv_load, life_exp) * 1e6L10 Life (hours)
l10_hours = pow(dynamic_cap / equiv_load, life_exp) * 1e6 / (60 * rpm)Variables
| Variable | Description | Default |
|---|---|---|
dynamic_cap | Dynamic Load Rating (C)(kN) | 50 |
equiv_load | Equivalent Dynamic Load (P)(kN) | 10 |
rpm | Rotational Speed(RPM) | 1500 |
life_exp | Life Exponent (p) | 3 |
How It Works
Rolling Bearing L10 Life
The L10 life is the number of revolutions (or hours) at which 90% of identical bearings will survive.
Formula
L10 = (C/P)^p x 10^6 revolutions
L10h = L10 / (60 N) (hours)
where C is the dynamic load rating from the manufacturer, P is the equivalent dynamic bearing load, N is speed in RPM, and p is the life exponent (3 for ball bearings, 10/3 for roller bearings).
Worked Example
A ball bearing with C=50 kN, operating load P=10 kN, at 1500 RPM.
- 01C/P = 50/10 = 5
- 02L10 = 5^3 x 10^6 = 125 x 10^6 = 125,000,000 rev
- 03L10h = 125,000,000 / (60 x 1500) = 1,388.9 hours
- 04At 8 hours/day, this is about 174 operating days.
Frequently Asked Questions
What does L10 mean?
L10 is the life that 90% of a group of identical bearings will reach or exceed. The median (L50) life is about 5 times the L10 life. Individual bearing life varies widely.
Should I use p=3 or p=10/3?
Use p=3 for ball bearings and p=10/3 (3.33) for roller bearings (cylindrical, tapered, spherical). This reflects the different contact geometry and fatigue behaviour.
How do I calculate the equivalent dynamic load P?
For combined radial (Fr) and axial (Fa) loads: P = X Fr + Y Fa, where X and Y are factors from the bearing catalogue that depend on the bearing type and the Fa/Fr ratio.
Ready to run the numbers?
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