Bearing stress formula
Bearing stress is the contact pressure between a fastener and the hole it presses against. It is checked alongside shear in bolted and pinned joints, because a hole can elongate and tear even when the bolt itself is strong enough.
Variables
| σb | Bearing stress | psi or Pa |
| F | Load on the fastener | lb or N |
| d | Bolt or pin diameter | in or mm |
| t | Plate or material thickness | in or mm |
Rearranged
t = F / (σb × d)
Worked example
A 12 mm bolt bears against a 10 mm thick plate carrying 6,000 N.
The projected area is d times t: 12 × 10 = 120 mm².
Divide force by area: 6,000 / 120 = 50 MPa.
Bearing stress uses the projected area, the diameter times the thickness, not the round hole area. If it is too high the hole elongates or the material tears out, so thin plates and soft materials often need larger bolts, washers, or doublers to spread the load.
Designing a bolted joint?
See the Clearance Hole Chart and Bolt Grade Chart.
Why projected area is used
The contact between a round bolt and a hole is curved, but bearing stress is calculated on the projected rectangle, diameter times thickness. This simplification gives a consistent, conservative number that matches how bearing failures actually occur, with the hole ovalizing in the load direction.
Bearing, shear, and tear-out
A bolted joint must pass several checks: the bolt in shear, the plate in bearing, and the material between the hole and the edge in tear-out. Bearing governs when plates are thin or holes are close together, which is why minimum edge distances and plate thicknesses exist in connection design.
FAQ
What is bearing stress?
The contact pressure between a fastener and the hole wall, found by dividing the load by the projected area, diameter times thickness.
Why use diameter times thickness for the area?
It is the projected bearing area. Using this rectangle rather than the curved contact gives a consistent, conservative bearing stress that matches real hole elongation.
What happens if bearing stress is too high?
The hole elongates and the plate can tear out. Fixes include a larger bolt, a thicker plate, washers, or greater edge distance.