Wood Shrinkage Calculator
Wood changes dimension as its moisture content (MC) changes below the fiber saturation point. This calculator predicts the dimensional change in a board when moisture content shifts from one level to another, using the species shrinkage coefficient method from the USDA Forest Products Laboratory Wood Handbook. Enter the initial dimension, the initial and final moisture content percentages, and the shrinkage coefficient for the applicable grain direction. The calculator returns the change in dimension and the final dimension. Use tangential coefficients for flat-sawn boards and radial coefficients for quarter-sawn boards.
Wood shrinkage formula
Change = Dimension × Coefficient × (MC₁ - MC₂)
Final dimension = Dimension - Change
Where MC₁ is initial moisture content (%) and MC₂ is final moisture content (%). If MC₂ is greater than MC₁, the wood swells and the change is positive, increasing the final dimension. If MC₂ is less, the wood shrinks. The coefficient is the fractional change per 1 percent MC change; values are from USDA Wood Handbook Table 4-3 for each species and direction.
Typical shrinkage coefficients
- Red oak: tangential 0.00369, radial 0.00158 per 1% MC change.
- Hard maple: tangential 0.00353, radial 0.00165 per 1% MC change.
- Walnut: tangential 0.00274, radial 0.00190 per 1% MC change.
- Cherry: tangential 0.00284, radial 0.00151 per 1% MC change.
- White pine: tangential 0.00247, radial 0.00122 per 1% MC change.
Wood shrinkage calculator: frequently asked questions
What causes wood to shrink or swell?
Wood is hygroscopic: it absorbs and releases moisture from the surrounding air. As moisture content rises above the fiber saturation point (roughly 28 to 30 percent), free water fills cell cavities but does not change dimensions. Below that point, bound water in cell walls leaves as wood dries, causing the cell walls to shrink.
What is the shrinkage coefficient?
The shrinkage coefficient (also called the dimensional change coefficient) is the fractional change in dimension per 1 percent change in moisture content. It differs by species and by grain direction. Tangential shrinkage is typically 1.5 to 2 times radial shrinkage. Values come from the USDA Wood Handbook.
What is the difference between tangential and radial shrinkage?
Tangential shrinkage occurs along the growth rings (flat-sawn face). Radial shrinkage occurs across the growth rings (quarter-sawn face). Flat-sawn boards move roughly twice as much as quarter-sawn boards, which is why quarter-sawn lumber is preferred for stable furniture.
What moisture content should interior woodwork be at?
The USDA Forest Products Laboratory recommends that interior woodwork equilibrate to the indoor equilibrium moisture content (EMC) of 6 to 8 percent for most of the continental US. Furniture or flooring should be conditioned to local EMC before installation to minimize seasonal movement.
Can I use this calculator for longitudinal (along-grain) shrinkage?
Longitudinal shrinkage is very small, typically 0.1 to 0.2 percent from green to oven-dry, and is usually ignored in joinery design. This calculator is intended for tangential and radial (across-grain) movement, which is significant in furniture and flooring.
Official sources
- USDA Forest Products Laboratory: Wood Handbook, FPL-GTR-190, Chapter 4 (Moisture Relations).
- USDA Forest Service Forest Products Laboratory: FPL Homepage.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.