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

Tongue thickness (mm)

Tongue thickness in millimeters.

Compute the groove width for a tongue joint by adding a 0.2 mm fitting clearance to the tongue 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]

Groove width (mm)

Groove width in millimeters, the tongue thickness plus a 0.2 mm clearance.

• 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.

• Ceiling Panel Expansion Gap Rule

  Recommend the tongue-and-groove ceiling panel expansion gap as 8 mm from 4 m field length and 5 mm below.

• Tongue Thickness

  Find tongue thickness from mating groove width after subtracting an explicit total fit clearance.