Predict how much a board will expand or contract as its moisture content changes — essential for joinery and panel design.
D is the initial dimension, S is the species shrinkage coefficient (% change per 1% change in moisture content), and ΔMC is the moisture content change.
Flat-sawn (tangential) boards move roughly twice as much as quarter-sawn (radial) boards for the same species — a key reason craftsmen choose quartersawn for table tops and instrument soundboards.
12″ Red Oak (flat-sawn), 20% → 8% MC → ΔD = 12 × 2.02 × 12 / 100 = 2.91″ shrinkage Wood only shrinks/swells across the grain — longitudinal movement along the length is negligible (< 0.1%) and can be ignored for most projects.