Use this workshop calculation to turn measured dimensions and the selected construction convention into a cut, spacing, fit, or material-planning value.

Screw head diameter (mm)

Required number input.

Pilot opening diameter (mm)

Required number input.

Countersink included angle (°)

Required number input.

Calculate conical countersink depth between pilot-hole diameter and screw-head diameter from included countersink angle. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Conical depth (mm)

The resulting conical depth returned as a number.

• Nominal dimensions, kerf, moisture movement, hardware clearances, wall squareness, and manufacturer instructions can change the required shop dimension. Measure the actual assembly and test critical joints on scrap before cutting finished material.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Complement the calculated dimension with a physical story stick, dry fit, or full-size layout. Follow the hardware, coating, adhesive, or machine manufacturer's limits where they differ from a rule of thumb.

• Screw Pilot Hole Calculator

  Compute pilot hole diameter and depth for a wood screw with 6 mm tip clearance.

• Chamfer Width Calculator

  Calculate the resulting chamfer width from chamfer depth and angle in degrees.

• Holzschraube Vorbohrung 07d

  Rule-of-thumb pilot diameter equal to 70% of a wood screw's outside diameter; adjust for screw and timber manufacturer guidance.