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Bolt Bearing Pressure Calculator

Enter the load and bolt geometry to find the bearing stress.

How it is calculated

Bearing pressure is the force carried by one bolt divided by the projected contact area: σ = F ÷ (d × t). F is the force in newtons (N), d the bolt diameter in millimetres and t the thickness of the plate being checked in millimetres. Because 1 N per mm² equals 1 MPa, the result is directly in megapascals. The tool shows the stress, the projected area d × t in mm² and the force it used. It uses the bolt diameter as the width of the contact, not the hole diameter, and it does not compare the answer with any allowable value. All three inputs must be above zero. Enter the force that goes through one bolt, not the total load on a group of bolts.

Worked example

A bolt of 16 mm diameter carries 20 kN through a 10 mm thick plate. Convert the force: 20 kN = 20000 N. Projected area: 16 × 10 = 160 mm². Bearing pressure: 20000 ÷ 160 = 125 N/mm², which is 125 MPa. The tool shows 125.00 MPa, an area of 160.00 mm² and a force of 20,000.00 N. If the plate were only 5 mm thick, the area would halve and the pressure double to 250 MPa.

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Common mistakes

  • Entering the force in kN. The field expects newtons, so typing 20 for 20 kN gives 0.13 MPa instead of 125 MPa, which is 1000 times too low.
  • Entering the total load of a joint with several bolts. The calculation is per bolt, so divide the load among the bolts first.
  • Using the combined thickness of several plates when only one plate bears on the bolt. Use the thickness of the plate you are checking.
  • Entering the diameter in inches or the thickness in centimetres. Both must be in millimetres, otherwise the area and the stress are wrong.
  • Treating the result as a pass or fail. The number is only the actual stress; it still has to be compared with the allowable bearing strength from the design code, and shear and net-section checks are separate.

About this calculator

Bearing pressure (or bearing stress) at a bolted connection is the contact stress between a bolt shank and the wall of the hole it passes through, calculated as the applied force divided by the projected area of contact — bolt diameter multiplied by plate thickness, not the full cylindrical surface area.

This simplified projected-area model is the standard approach used in steel design codes such as AISC and Eurocode 3 to check that a connection won't fail by the bolt hole elongating or tearing out (bearing failure), one of several failure modes — alongside bolt shear and plate net-section rupture — that must each be checked independently in a bolted joint.

Structural and mechanical engineers compute bearing stress to confirm it stays below the material's allowable bearing strength, which is typically a multiple of the plate's yield or ultimate strength specified in the applicable design code.

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