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

Stock Thickness Millimeters (mm)

Required number input.

One-third-rule tenon thickness and equal shoulder widths from stock thickness; these are starting dimensions, not a strength check. 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]

Tenon Thickness Millimeters (mm)

The resulting tenon thickness millimeters returned as a number.

Shoulder Each Side Millimeters (mm)

The resulting shoulder each side millimeters 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.

• Feder Nut Masse 1 3 Regel

  One-third-rule tongue thickness from stock thickness and groove width after a user-selected fitting clearance.

• Tenon Shoulder

  Calculate equal tenon shoulder widths when a centered tenon is cut from a wider stock edge.

• Nail Length Rule

  Minimum nail length from the thickness of the attached board and a separately chosen penetration depth into the receiving member; not a withdrawal-capacity check.