Drawing No. EH–ME–001 // Mechanical Engineering
Bearing Life Calculator
Reviewed August 2026
Find a rolling-element bearing's L10 basic rating life from its dynamic load rating and equivalent applied load, per ISO 281, in both revolutions and operating hours.
What problem does this solve?
Rolling-element bearings don't have a fixed lifespan — their fatigue life depends strongly on how hard they're loaded relative to their rated capacity, following a steep power-law relationship. This calculator finds L10 life — the number of revolutions (or hours) at which 90% of a population of identical bearings under identical conditions would still be running without fatigue failure — from load rating, applied load and speed.
Inputs
Results
Background
L10 = (C/P)p, in millions of revolutions, where C is the bearing's basic dynamic load rating (from the manufacturer's catalog), P is the equivalent dynamic bearing load, and p is a life exponent: p = 3 for ball bearings, p = 10/3 for roller bearings. L10 is the life that 90% of an identical bearing population would statistically exceed under identical conditions before fatigue failure.
L10h = L10 × 10⁶ / (60 × n), where n is rotational speed in rpm. This converts the revolution-based basic rating life into operating hours, which is usually the more practical quantity for maintenance planning.
Because life scales with the load ratio raised to the third power (or 10/3 for roller bearings), even a modest increase in applied load causes a disproportionately large drop in bearing life — doubling the load cuts a ball bearing's L10 life to roughly 1/8th, all else equal. This is why accurately estimating equivalent dynamic load matters far more for bearing life than for many other machine elements.
Frequently asked questions
Practical questions about inputs, assumptions and interpretation.
L10 is a statistical rating, not a guarantee — it's the life exceeded by 90% of a large population of nominally identical bearings run under the same load and speed. Any individual bearing could fail earlier or run much longer; L10 is a design and comparison basis, not a warranty figure for one specific bearing.
Ball bearings have point (Hertzian) contact with the raceway, while roller bearings have line contact — this difference in contact geometry changes how stress concentrates and how fatigue life scales with load, empirically captured by the different exponent (3 for ball, 10/3 for roller) in the ISO 281 equation.
Real applications often need the modified rating life, Lnm = a₁ × aISO × L₁₀, which applies a reliability adjustment factor (a₁, for reliability other than 90%) and a combined lubrication/contamination/material factor (aISO) that can significantly increase or decrease life versus the basic L10 shown here. Poor lubrication or contamination in particular can reduce real life well below the basic L10 estimate.