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

Board Width Millimeters (mm)

Required number input.

Movement Per Percent Moisture (1/%)

Required number input.

Moisture Increase Percent (%)

Required number input.

Minimum total free space for expected across-grain board expansion from a supplied movement coefficient and moisture-content change. 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]

Total Gap Millimeters (mm)

The resulting total gap 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.

• Holz Quellung

  Expected across-grain wood swelling over a rising dry-basis moisture content, using a species- and direction-specific measured movement coefficient.

• Holz Schwindmass

  Expected across-grain wood shrinkage over a falling dry-basis moisture content, using a species- and direction-specific measured movement coefficient.

• Wood Movement Expansion

  Estimate cross-grain wood expansion from starting board width, a species/orientation coefficient per moisture-content point, and moisture increase.