Bearing load calculator
A radial load applied between two bearings divides between them in inverse proportion to the distances. Enter the load and the two distances to get the reaction at each bearing; add the bushing bore and length to see the specific load in N/mm².
Use the calculator for a shaft or pin supported at two points with one radial load between them: a pivot pin in two bushings, a pump shaft between two bearings, a roller on a shaft. For several loads, run each load separately and add the reactions at each bearing.
Formula: reactions of a simply supported shaft
For a load P at distance L1 from bearing 1 and L2 from bearing 2, moment equilibrium about each bearing gives R1 = P · L2 / (L1 + L2) and R2 = P · L1 / (L1 + L2). The bearing nearer the load carries more; if the load sits over one bearing that bearing carries all of it. R1 + R2 always equals P.
The formulas assume the load is between the bearings. For an overhung load outside the span, one reaction becomes negative (it acts the other way) and its magnitude can exceed P; that case is worth a sketch and a message to us rather than a calculator.
From reaction to specific load
Plain bearing materials are rated by specific load, the reaction divided by the projected area of the bushing: p = R / (d × L), in N/mm² (1 N/mm² = 1 MPa ≈ 145 psi). Enter the bore and length and the tool reports p at each bearing. Compare it with the limit in the product pages: for example, JBM-ST hardened steel bushings are rated to 250 N/mm² static, cast bronze and bimetal bushings to lower values that depend on the alloy.
Static limits are not running limits. A bushing that moves also has a PV limit, the product of specific load and sliding speed; use the plain bearing PV calculator for that check.
When the two bearings see very different loads, it is normal to specify a longer or different-material bushing at the heavily loaded end rather than oversizing both.
Worked example
A bucket pin carries P = 120 kN between two bushings, 120 mm from bearing 1 and 80 mm from bearing 2. R1 = 120 × 80 / 200 = 48 kN and R2 = 120 × 120 / 200 = 72 kN. With 60 mm bore × 70 mm long bushings, the projected area is 4,200 mm², giving 11.4 N/mm² at bearing 1 and 17.1 N/mm² at bearing 2, both far inside the static rating of a hardened steel or bimetal pin bushing.
Assumptions and limits
The calculation is plane statics. It ignores:
- Shaft weight and bearing friction, which are usually small compared with the applied load.
- Misalignment and shaft deflection, which concentrate load at the bushing edges; long bushings in flexible shafts see higher edge pressure than p suggests.
- Axial (thrust) loads, which are carried by flanges or thrust washers and are not part of the radial reaction.
- Dynamic and shock factors. Multiply P by the service factor of your machine before comparing with a static limit.
Frequently asked questions
Which bearing is bearing 1?
Whichever you choose; the tool is symmetric. Label the sketch, enter the distance from the load to that bearing as L1, and the results follow the same labels.
What if the load is not between the bearings?
Then the shaft is overhung and one reaction reverses direction. The formulas above no longer apply directly; send the sketch and we will work the reactions with you.
Why does the tool need the bushing bore and length?
To convert the reaction into a specific load, which is how plain bearing materials are rated. The projected area is bore × length, not the curved surface area.
Can I use kN or lbf?
Enter newtons or pounds-force according to the unit switch; type 120000 for 120 kN. Results above 10 kN are displayed in kN.
Know the load? We will propose the material.
Send the reactions, the pin diameter and the bushing length with the application. Our engineers return a material, a size and a quotation within 12 hours.