Mechanical & Civil Engineering
Journal Bearing Sommerfeld Number Calculator
Calculate the Sommerfeld number for a hydrodynamic journal bearing to assess lubrication regime.
Your inputs
Change any value to update the result instantly.
Sommerfeld number
0.1125
r/c ratio
500
Speed
30 rev/s
Unit load
2 MPa
Regime
1
What this calculator does
Journal Bearing Sommerfeld Number Calculator: Applies the standard machine-element relationship used in design textbooks so the capacity, rating or geometry can be worked out step by step.
What your result means
The headline figure is the capacity, rating or geometric result for the element you described. Compare it with the manufacturer's rating and your required service factor.
Formula and working
S = (r/c)² × (μN/P)
- 1
Collect the inputs
Journal radius = 25 mm; Radial clearance = 0.05 mm; Lubricant viscosity = 0.03 Pa·s; Rotational speed = 1,800 rpm; Unit load on projected area = 2 MPa
- 2
Apply the formula
S = (r/c)² × (μN/P)
- 3
Result
Sommerfeld number = 0.1125
Frequently asked questions
Symbols and assumptions
- radius
- Journal radius (mm)
- clearance
- Radial clearance (mm)
- viscosity
- Lubricant viscosity (Pa·s)
- speed
- Rotational speed (rpm)
- load
- Unit load on projected area (MPa)
- • Standard textbook geometry and steady operating conditions are assumed; shock, misalignment and wear factors are not applied automatically.
- • Material and surface-finish allowances must be chosen by the user for their actual component.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • This is an educational estimate for learning and checking, not a design deliverable.
- • Real design must follow the governing code or standard for your jurisdiction and be reviewed and signed off by a qualified engineer.
- • Safety factors, load combinations and material certification are the responsibility of the designer, not of this page.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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