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

Initial Width Millimeters (mm)

Required number input.

Initial Moisture Percent (%)

Required number input.

Final Moisture Percent (%)

Required number input.

Movement Per Percentage Point (1/%)

Required number input.

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

Swelling Millimeters (mm)

The resulting swelling 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 Schwindmass

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

• Board Expansion Gap

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

• Wood Movement Expansion

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