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

Joint width (mm)

Required number input.

Each end pin width (mm)

Required number input.

Tail count

Required integer input.

Each tail width (mm)

Required number input.

Solve equal interior pin width from joint width, two end pins, tail count, and equal tail width. 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]

Interior pin width (mm)

The resulting interior pin width 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.

• Dovetail Tail Count

  Count complete dovetail tails that fit an available joint width after reserving equal end pins and interior pin widths.

• Dovetail Spacing

  Lay out equal dovetail tails between two end pins and equal interior pins; report tail width and center pitch.

• 4-Inch Baluster Spacing

  Count equal-width balusters and calculate equal clear gaps, including both end gaps, so none exceeds a four-inch maximum.