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Bearing Fault Calculator

Harmonics of Inner Race • Outer Race • Ball Spin

Live calculation • Entek IRD / ISO 18436 compatible

📍 Shaft & Bearing Geometry

Shaft Speed (RPM)

RPM

Typical motor speeds: 900, 1200, 1800, 3600 RPM

Number of Balls / Rollers (N_b)

Contact Angle β (°)

0° for most radial bearings

Ball Diameter (d)

inches

Pitch Diameter (D)

inches

Note: Diameters must use the same unit (inches or mm). The ratio d/D is unitless.
Data from bearing manufacturer catalog recommended. Values shown are example for a typical 6205-size bearing.

Fundamental Defect Frequencies

Harmonics (1× to 10×)

Outer Race (BPFO)

Inner Race (BPFI)

Ball Defect (2×BSF)

Harmonic	BPFO (Hz)	BPFO (CPM)	BPFI (Hz)	BPFI (CPM)	Ball (Hz)	Ball (CPM)

Formulas used (CPM mode):
BPFO = (N_b/2) × RPM × (1 − (d/D)cosβ)
BPFI = (N_b/2) × RPM × (1 + (d/D)cosβ)
BSF = (D/(2d)) × RPM × [1 − ((d/D)cosβ)²]
Ball defect frequency = 2 × BSF (standard for rolling-element defects)
All harmonics are multiples of the fundamentals above.

Units: Hz = CPM / 60 • Perfect for spectrum analysis (Entek IRD, CSI, SKF, etc.)

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Enter shaft RPM and bearing geometry above.
Click CALCULATE to see all defect frequencies and their harmonics.

Load realistic example (1800 RPM motor) →