Green Wood Shrinkage Calculator — Predict Drying Dimensions

Green wood typically shrinks 5-12% tangentially (across the growth rings), 3-6% radially (along the rings), and only 0.1-0.2% longitudinally (along the grain). The exact amount depends on the species. Oak, for example, shrinks about 10.5% tangentially.

The fiber saturation point (FSP) is typically around 28% moisture content. Above this point, wood contains free water in cell cavities and does not shrink. Shrinkage only begins as moisture drops below the FSP, when bound water leaves the cell walls.

For interior furniture in a heated home, aim for 8-12% MC. For outdoor projects, 15-18% MC is appropriate. Air-dried timber in the UK typically reaches 15-20% MC. Kiln-dried timber is usually 8-12% MC.

The growth ring structure causes differential shrinkage. Ray cells running radially act as restraints that reduce radial shrinkage. The ratio of tangential to radial shrinkage (T/R ratio) is typically 1.5-2.5, with higher ratios indicating more tendency to warp and distort.