Enter the tensile stress area, ultimate tensile strength, and safety factor into the calculator to estimate the allowable axial tensile load a threaded fastener can carry. Note: this calculator does not calculate thread stripping/pull-out; true pull-out (thread stripping) depends on thread engagement length, thread geometry, and the shear strength of the weaker internal/external thread material.

Thread Tensile Load (Axial) Calculator

Tensile Load
Fastener Count

Enter any 3 values to calculate the missing variable (based on F = (As × Su) / SF)

Thread Tensile Load (Axial) Formula

The following formula is used to estimate the allowable axial tensile load of a threaded fastener based on tensile stress area, ultimate tensile strength, and a safety factor:

F = (A_s * S_u) / SF

Variables:

  • F is the allowable axial tensile load (lbf)
  • As is the tensile stress area (in²)
  • Su is the ultimate tensile strength (psi)
  • SF is the safety factor (unitless)

To estimate the allowable axial tensile load, multiply the tensile stress area by the ultimate tensile strength (in² × lbf/in² = lbf) and then divide by the safety factor.

What is Thread Tensile Load Capacity?

Thread tensile load capacity (axial) is the maximum axial force a threaded fastener can carry before tensile failure of the fastener’s cross-section (typically estimated using the fastener’s tensile stress area). This is different from thread stripping/pull-out, which is governed by the shear strength of the threads and the length of thread engagement.

How to Calculate Thread Tensile Load Capacity?

The following steps outline how to calculate the allowable axial tensile load.

  1. First, determine the tensile stress area (As) in square inches.
  2. Next, determine the ultimate tensile strength (Su) in psi.
  3. Next, determine the safety factor (SF).
  4. Next, gather the formula from above: F = (As × Su) / SF.
  5. Finally, calculate the allowable axial tensile load (F) in lbf.
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

tensile stress area (As) = 0.5 in²

ultimate tensile strength (Su) = 60,000 psi

safety factor (SF) = 1.5

F = (0.5 × 60,000) / 1.5 = 20,000 lbf (≈ 89.0 kN)