Wood Shrinkage Calculator
Work out how much a board will shrink or swell as it dries or takes on moisture. Enter the width, the starting and target moisture content, and either a species and saw cut or your own coefficient.
How to calculate wood shrinkage
- Enter the current board width in inches.
- Enter the starting and target moisture content in percent.
- Pick a species and saw cut, or enter your own coefficient, then read the change.
Examples
Oak board drying from 12% to 7%
Width 10 in, 12% to 7% moisture, oak, flatsawn
Shrinks about 0.18 in to 9.82 in (1.83%)
Frequently asked questions
How much does wood shrink?
It depends on species, saw cut and how far the moisture content changes. A 10 inch flatsawn oak board drying from 12 percent to 7 percent shrinks about 0.18 inch across its width.
Why does quartersawn wood move less?
Quartersawn boards shrink along the radial direction, which is roughly half the tangential movement of a flatsawn board. That stability is why quartersawn lumber is favored for wide panels.
What is the fiber saturation point?
It is the moisture content, near 28 percent, below which wood starts to shrink and swell. Above it the wood holds free water in its cavities and does not change size, so this tool clamps moisture to 28 percent.
What is a dimensional change coefficient?
It is the fractional change in a dimension for each 1 percent change in moisture content. Multiply it by the width and the moisture change to get the movement in inches.
Should I allow for this movement when I build?
Yes. Let wide panels float in grooves, use slotted fastener holes for tabletops, and acclimate lumber to the room before building so it settles near its final moisture content.
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