Engineering tool · vibration analysis
BPFI / BPFOBearing Fault Frequency Calculator
Calculate theoretical inner-race, outer-race, rolling-element and cage defect frequencies from bearing geometry.
Defect frequencies
Calculate bearing diagnostic orders
The formulas assume pure rolling, fixed outer race and negligible slip. Use the exact internal geometry where available.
RESULT / 02
Fault frequencies
Theoretical values without rolling-element slip
Shaft rotational frequency—1.000× shaft order
Inner race · BPFI——
Outer race · BPFO——
Ball spin · BSF——
Cage · FTF——
BPFI/BPFO = n/2 · fr · (1 ± Bd/Pd · cos θ)
Interpretation
Use orders and sidebands together
Actual spectra can shift because of slip, load, speed variation and measurement resolution.
01 / RACESBPFI and BPFO
Repeated rolling-element contact with a defect on the inner or outer race.
02 / ELEMENTSBSF and FTF
Rolling-element spin frequency and fundamental train/cage frequency.
03 / DIAGNOSISFrequency is not proof
Confirm harmonics, modulation, sidebands, phase and operating condition before diagnosing a fault.