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

Stock thickness (mm)

Required number input.

Chosen thickness fraction

Required number input.

Calculate target dado depth from board thickness and an explicitly chosen fraction of that thickness. 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]

Dado depth (mm)

The resulting dado 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.

• 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.

• Half-Lap Cross Joint Calculator

  Compute the lap thickness and cut depth that halve a cross-lapped board.

• Biscuit Slot Depth

  Target insertion depth on each side of a centered biscuit joint from biscuit width plus a chosen glue clearance.