How much does green wood shrink?

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.

What is fiber saturation point?

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.

What moisture content should I dry wood to?

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.

Why does wood shrink more tangentially than radially?

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.

WoodCalcs

Green Wood Shrinkage Calculator — Predict Drying Dimensions

Predict how much green wood will shrink as it dries to your target moisture content.

Wood Species

Green Length

Longest dimension of the area

Green Width

Tangential direction

Green Thickness

Radial direction

Target Moisture Content

Desired final MC (interior: 8-12%, outdoor: 15-18%)

How We Calculate This

This calculator predicts dimensional changes as green wood dries to a target moisture content.

Shrinkage formula

Shrinkage % = Total shrinkage % x (FSP - Target MC) / FSP

Wood only shrinks below the fiber saturation point (default 28% MC). The total shrinkage values are species-specific, measured from green to oven-dry (0% MC).

Assumptions

Width is assumed to be the tangential direction (flat-sawn boards). Thickness is the radial direction. Longitudinal shrinkage is negligible at approximately 0.1%.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.