Bearing L10 Life Calculator
The L10 life is the fundamental bearing selection parameter: it estimates how long 90% of a group of identical bearings will survive under a given load and speed. This calculator uses the ISO 281 basic rating life formula. Enter the bearing's dynamic load rating C (from the manufacturer catalogue), the equivalent dynamic load P applied to the bearing, and the operating speed. The result is L10 in millions of revolutions and in operating hours.
ISO 281 L10 bearing life formula
L10 = (C / P)p (millions of revolutions)
Lh10 = (106 / 60N) × L10 (operating hours)
p = 3 (ball bearings), p = 10/3 (roller bearings)
Where: C = basic dynamic load rating (N) from catalogue, P = equivalent dynamic bearing load (N), N = rotational speed (RPM), p = life exponent per ISO 281:2007 Section 5.
Notes on bearing selection
- Always verify the bearing's limiting speed (thermal speed) and maximum permissible speed from the catalogue.
- Apply a lubrication viscosity correction (kappa = actual viscosity / required viscosity) and contamination factor for modified L10m life per ISO 281.
- For shock loads or vibration, apply a service factor to P before entering it here.
- Consult the specific bearing manufacturer's catalogue (SKF, NSK, Schaeffler/FAG) for accurate C and C0 values for your bearing reference.
Bearing L10 life calculator: frequently asked questions
What is L10 bearing life?
L10 (also written L(10)) is the basic rating life at which 10% of a large group of identical bearings will have failed (90% reliability). It is expressed in millions of revolutions (L10) or operating hours (Lh10). The ISO 281 formula is L10 = (C/P)^p, where C is the basic dynamic load rating (N), P is the equivalent dynamic bearing load (N), and p is the life exponent (3 for ball bearings, 10/3 for roller bearings).
What is the basic dynamic load rating C?
The basic dynamic load rating C is the constant radial load that a bearing can theoretically carry for 1 million revolutions without material fatigue failure of the inner ring, outer ring, or rolling elements. It is published in the bearing manufacturer's catalogue and depends on the bearing size and type. For example, a 6205 deep groove ball bearing has C = 10.8 kN.
How is equivalent dynamic load P calculated?
For combined radial and axial loads, P = X * Fr + Y * Fa, where Fr is the radial load, Fa is the axial load, and X, Y are bearing-specific factors from the catalogue. For purely radial loads, P = Fr. For purely axial loads (thrust bearings), P = Fa. The X and Y values depend on the bearing type and the ratio Fa/(C0), where C0 is the static load rating.
What are typical L10 design lives for industrial bearings?
ISO 281 and bearing catalogues suggest typical design lives: electric motors 20,000 to 40,000 h; pumps 20,000 to 30,000 h; centrifuges 30,000 to 60,000 h; gearboxes 20,000 to 30,000 h; conveyors 20,000 to 30,000 h. Bearing selection should target an L10 life at least equal to or greater than the required design life.
What is the modified rating life Lnm?
ISO 281:2007 introduces the modified rating life Lnm = a1 * aISO * L10, where a1 is the reliability factor (1.0 for 90% reliability, 0.62 for 95%) and aISO is the life modification factor accounting for lubrication, contamination, and material. The full Lnm calculation requires detailed knowledge of operating viscosity and contamination class from ISO 4406.
Official sources
- ISO 281:2007 Rolling bearings: Dynamic load ratings and rating life: ISO 281:2007.
- NIST Standard Reference Database (material properties): nist.gov/srd.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.