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

Tenon thickness (mm)

Required number input.

Total fit clearance (mm)

Required number input.

Size mortise width to receive a measured tenon thickness plus chosen side-to-side fit clearance. 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]

Mortise width (mm)

The resulting mortise 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.

• Biscuit Slot Depth

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

• Dado Width

  Allow a dado to fit a measured panel thickness with explicit total width clearance.

• Frame Rabbet Depth

  Size a glazing-frame rabbet from measured glass-and-backing stack thickness plus bedding clearance.