**Related Resources: calculators**

### Thread Yield and Tensile Strength Equation and Calculator

**Fastener and Screw / Bolt Design, Formula and Calculations**

The following Equation and Calculator will determine the working loads base on the ultimate yield strength threaded connections.

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Ultimate Strength of a thread

y_{min} = s_{yield} x a

Ultimate Tensile Strength of a thread

s_{tensile} = t_{min} x a

Shear Strength of a thread

S_{sy} = p_{r} x s_{yield}

Where:

y_{min} = Minimum Yield of bolt threads engaged (lbs)

s_{yield} = Minimum yield strength of the bolt grade, ASTM, SAE, etc. (psi)

s_{tensile} = Ultimate Yield Strength (lbs)

t_{min} = Minimum tensile strength of the bolt grade, ASTM, SAE, etc. (psi)

S_{sy} = Working axial load of fastener bolt (lbs)

a = Stress area of thread (in^{2})

p_{r} = Percent expressed as decimal, e.g. 60% = 0.6 - This is the factor of safety (FOS) for the design application

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