Engineering tools · Bearing life

Bearing Life (L10h) Calculator

The basic ISO 281 rating life (L10h) tells you how long half the story is — it assumes ideal lubrication. This tool also folds in the viscosity ratio κ from the Viscosity Ratio Calculator, since inadequate film thickness is one of the biggest gaps between a bearing's catalog life and its real service life.

Enter the catalog load rating and operating conditions to get the basic L10h life, then see how lubrication and contamination stretch or shrink it.

EXACT L10/a1 · GUIDELINE aISO RANGE
01 Bearing type & load rating
From the bearing manufacturer's catalog for this specific designation — not derivable from bore/OD alone.
Above 125°C, bearing steel loses hardness and C is reduced by a documented temperature factor (ft) — a separate effect from the κ/lubrication correction below. Use the same operating temperature you used to determine κ.
02 Applied load
For combined radial + axial loading, calculate P = X·Fr + Y·Fa using the X/Y factors from the bearing's catalog page first, then enter that P here.
03 Speed
04 Lubrication & contamination
05 Reliability target
BASIC LIFE L10
–
Mrev
BASIC LIFE L10h
–
hours
a1 FACTOR
–
ADJUSTED LIFE, Lnmh (GUIDELINE RANGE)
–
–
Fill in the load rating, applied load, speed, and lubrication condition to see the adjusted life.
FACTOR BREAKDOWN
Life exponent, p–
Temperature factor, ft–
Temp-adjusted load rating, Ct–
Ct / P ratio–
a1 (reliability)–
aISO range (guideline)–

Method: L10 = (Ct/P)^p (p = 3 for ball bearings, 10/3 for roller bearings) and L10h = 10⁶/(60n) × L10 are the exact ISO 281 basic rating life equations, using the temperature-adjusted load rating Ct = ft × C. The temperature factor ft (bearing steel hardness reduction above 125°C: ft=1.00 at 125–150°C, 0.95 at 175°C, 0.90 at 200°C, 0.75 at 250°C, linearly interpolated between points) is verified against a published NSK technical bulletin (TI/E/0102) — a genuinely separate effect from the κ/lubrication correction below, since this one reflects reduced material hardness, not oil film thickness. The reliability factor a1 uses the standard ISO 281 table. The aISO life‑modification factor — which in the full ISO 281:2007 method depends on κ, a contamination factor eC, and the fatigue load limit Cu via a digitized diagram / multi‑parameter equation — is approximated here as a qualitative guideline range based on κ and contamination level, in the same practical spirit as the plain‑bearing viscosity guideline elsewhere in this toolset. It is not the official ISO 281:2007 aISO diagram. For warranty‑critical, high‑reliability, or heavily loaded applications, use the manufacturer's own ISO 281:2007 calculation (which requires the bearing's fatigue load limit Cu) rather than this guideline range.

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