Bolt Shear and Bearing Stress Calculator

Check the shear stress in the bolts, the bearing stress on the plate and the punching shear around a hole for a bolted or pinned joint.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

In a lap joint each bolt is cut across one plane (single shear). When a plate sits between two straps the bolt is cut across two planes (double shear) and the shear stress halves. The bearing stress is the force divided by the bolt diameter times the plate thickness. Punching shear is the force divided by the circumference of the hole times the plate thickness.

Enter the force, the bolt diameter, the plate thickness, the number of bolts and the shear planes. Add allowable stresses to get a ratio for each check.

Formulas used

  • \tau = \dfrac{F}{n_b\,n_s\,\pi d^2/4}
  • \sigma_b = \dfrac{F}{n_b\,d\,t}
  • \tau_c = \dfrac{F}{\pi d t}

Worked example

With the default numbers in the calculator above:

  1. Area of one bolt shank: 201.06 mm²
  2. Force on each bolt: 20000 N
  3. Single shear stress in the bolts: 99.472 MPa
  4. Bearing stress on the plate: 125 MPa
  5. Punching shear stress around the hole (if the bolt head or the pin were pushed through the plate): 39.789 MPa

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

Single or double shear?

Count the planes the bolt would be cut along. Two plates lapped together is single shear. A plate between two straps is double shear.

What if the thread is in the shear plane?

Use the thread root area, or the tensile stress area, instead of the shank area. The smaller area gives a higher stress.

Is this a joint design?

No. Edge distances, tear-out, net-section tension, prying and the structural standard capacity rules all need checking.

Related calculators

Further reading: Standard machine design and strength of materials texts (bolted joint stresses); AS 4100 for structural steel bolted connections.

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