Wood Shrinkage Calculator
Tangential, radial and volumetric shrinkage by species — Wood Handbook 2021 Eq. 4-9.
Pick a species (16 verified presets: acacia, rubberwood, eucalyptus, teak, oak, ash, beech, pine...) or enter a custom green→OD shrinkage % and FSP, choose start and end MC, and get the percentage shrinkage and final dimension for tangential (board width), radial (board thickness) or volumetric change. Above FSP the dimension is constant; the tool clamps MC to FSP for the math.
FAQ
Why doesn't the wood shrink above FSP?
Above the fibre-saturation point (FSP ≈ 30% for most species) the cell walls are fully saturated and the extra water sits in the cell cavities. Cavity water doesn't change dimension, only the bound water in the cell walls does. So the wood only starts to shrink once MC drops below FSP — that's why kiln operators target an MC well below FSP for stable furniture stock.
Tangential vs radial — which is bigger?
Tangential (across the growth rings, along the board width of flat-sawn stock) is always larger than radial (along the rays, across the board thickness). Typical ratio: tangential is 1.5–2× radial. For oak the values are 10.5% vs 5.6% (WH Tables 4-3/4-4); for radiata pine 3.9% vs 2.1% (green→12% MC).
How do I account for both width and thickness?
Run the calculator twice: once tangential with the board width, once radial with the board thickness. The board-shrinkage bulk view (on the G3 hub page) does both at once and adds longitudinal (usually negligible, ~0.1–0.3%) to give the volumetric change. Planing allowance (2.4–3 mm/face) is separate — see the rough-sizing tool.