Bearing size calculator
Bore × outside diameter × length is how every plain bearing is specified. Enter the three dimensions and get the wall thickness, circumferences, material volume, estimated mass and projected bearing area, in millimetres or inches.
Type the dimensions as they appear on the drawing or the part marking. The material list sets the density for the mass estimate; the projected area (bore × length) is the value used for specific-load calculations on plain bearings.
How to read a bearing size
Plain bearings are written as three numbers in a fixed order: bore (inside diameter, d) × outside diameter (D) × length (L). A 20 × 25 × 30 bushing has a 20 mm bore, a 25 mm outside diameter and is 30 mm long, which makes the wall 2.5 mm thick. Catalogue references such as JBM-ST 55 × 65 × 45 follow the same order, and so should an enquiry.
Flanged bushings add the flange diameter and flange thickness as separate dimensions; thrust washers are written as inside diameter × outside diameter × thickness. The calculator handles the cylindrical part only; put the flange on the drawing.
Formulas used
Everything is elementary geometry of a hollow cylinder. Lengths are converted to millimetres internally and shown in the unit you selected.
| Quantity | Formula | Use |
|---|---|---|
| Wall thickness | t = (D − d) / 2 | Minimum wall for wrapped and composite bushings; press-fit deformation |
| Inner circumference | C_i = π · d | Strip length for a wrapped bushing before slitting allowance |
| Outer circumference | C_o = π · D | Sleeve outer development, marking, coating area |
| Ring cross-section | A_r = π / 4 · (D² − d²) | Bar-stock selection, material take-off |
| Projected bearing area | A_p = d · L | Specific load p = F / A_p for plain bearings |
| Volume | V = A_r · L | Material quantity, mass estimate |
| Mass | m = V · ρ | Shipping weight and price estimate |
Worked example
A cast bronze bushing 40 × 50 × 60 mm: wall thickness 5 mm; inner circumference 125.7 mm; outer circumference 157.1 mm; ring cross-section 706.9 mm²; projected area 2,400 mm²; volume 42.4 cm³; mass at 8.9 g/cm³ about 377 g per piece, or 37.7 kg per hundred. Under a 12 kN radial load the specific load would be 12,000 / 2,400 = 5 N/mm², well inside the static limit for C93200 bronze.
Densities used for the mass estimate
The densities are nominal handbook values for the material class. Grooves, oil holes, chamfers and the porosity of sintered bronze reduce the real mass; a steel-backed composite has a thin PTFE or POM layer that hardly changes the mass of the steel shell. For a quotation we weigh the sample.
| Material | Density g/cm³ |
|---|---|
| Cast bronze C93200 / SAE 660 | 8.9 |
| Aluminium bronze C95400 | 7.6 |
| Brass | 8.5 |
| Sintered bronze (oil-impregnated) | 6.8 |
| Carbon and alloy steel | 7.85 |
| Steel-backed bimetal | 7.9 |
| Steel-backed PTFE composite | 7.6 |
| POM (acetal) | 1.41 |
| Nylon PA6 / PA66 | 1.14 |
Frequently asked questions
Is bore the same as inside diameter?
Yes. Bore, inside diameter, ID and d all mean the diameter of the hole the shaft or pin runs in. Outside diameter, OD and D mean the surface that sits in the housing.
Why does the calculator show projected area?
Because plain bearing load ratings are specific loads in N/mm² (or psi) referred to the projected area d × L, not to the curved surface. Divide your radial load by this area to compare with a material limit.
How accurate is the mass?
Within a few percent for a plain sleeve in the selected material. Oil grooves, holes, chamfers and flanges change it; for a firm shipping weight we weigh the sample part.
Can I enter inch sizes?
Yes. Switch to inch and enter decimal inches; 1 1/4 in is 1.25. Results are shown in inches, square inches and cubic inches, with mass in grams or kilograms.
Have a size? Get a price for it.
Send bore × outside diameter × length with the material and quantity. Quotation within 12 hours, free sample, no minimum order.