Bearing Parameters
0° for deep-groove ball bearings and cylindrical rollers
Results
Enter bearing parameters and click Calculate.
How This Calculator Works
This calculator uses the standard geometric formulas for rolling-element bearing defect frequencies. All four frequencies — BPFO, BPFI, BSF, and FTF — are functions of the bearing’s internal geometry and shaft rotational speed.
The preset bearing models use geometry data from published manufacturer specifications. For bearings not listed, select “Custom / Manual Entry” and enter the parameters from the bearing datasheet. The pitch diameter can be approximated as (bore + OD) / 2 if not directly listed.
For a step-by-step walkthrough of each formula with worked examples, see How to Calculate Bearing Defect Frequencies from a Datasheet.
Formulas
BPFO (Outer Race)
BPFO = (N/2) × fr × (1 - (Bd/Pd) × cosα)BPFI (Inner Race)
BPFI = (N/2) × fr × (1 + (Bd/Pd) × cosα)BSF (Ball Spin)
BSF = (Pd/(2×Bd)) × fr × (1 - (Bd/Pd)² × cos²α)FTF (Cage)
FTF = (fr/2) × (1 - (Bd/Pd) × cosα)Important Notes
- Slip: Real bearings experience 1–3% slip under light load, reducing actual frequencies slightly below calculated values. Monitor a ±3% band around each frequency.
- Variable speed: All defect frequencies scale linearly with shaft RPM. For VFD-driven equipment, recalculate at each operating speed.
- Harmonics: As defects grow, energy appears at 2×, 3×, and higher multiples of the fundamental defect frequency.
- Contact angle: Use 0° for deep-groove ball bearings. Angular contact bearings typically use 15°, 25°, or 40°.