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Fastener Calculators

Thread Engagement Calculator

Minimum thread engagement depth so the threads are stronger than the bolt itself.

Enter values

Results update as you type.

Result

Minimum engagement

4.92 mm

As a multiple of diameter
0.49 × D
Recommended tapped depth
9.15 mm
Threads engaged
3.3
Bolt stress area
57.99 mm²
Rule of thumb
10 mm in steel, 20 mm in aluminium

About the Thread Engagement Calculator

Minimum thread engagement depth so the threads are stronger than the bolt itself.

Also known as: minimum thread engagement, tapped hole depth, thread depth calculator, screw engagement.

How to use this calculator

  1. Enter bolt diameter, thread pitch, bolt tensile strength, tapped material.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

Le = (A_s × bolt strength) / (shear strength × π × D × 0.75)

Worked example

Using the values pre-filled in the calculator above:

  • Bolt diameter = 10 mm
  • Thread pitch = 1.5 mm
  • Bolt tensile strength = 800 MPa
  • Tapped material: Steel (400 MPa shear)

the calculator returns:

  • Minimum engagement: 4.92 mm
  • As a multiple of diameter: 0.49 × D
  • Recommended tapped depth: 9.15 mm
  • Threads engaged: 3.3