Wood movement
How much a board or panel will swell and shrink across its width from species shrinkage coefficients and moisture change, flatsawn versus quartersawn, equilibrium moisture content from temperature and humidity, and gaps for panels, tops, and breadboards.
Added
Works with
- Wood species Woodworkingshrinkage, density and stability for many more species, with a link back here for the ones this tool has coefficients for
How to use it
Wood moves across its width as its moisture content (MC) changes; along its length the change is negligible. Width change ΔW = W × C × ΔMC, where C is the dimensional change coefficient per 1% MC from the USDA Wood Handbook (Table 13-5): tangential for flatsawn faces, radial for quartersawn, the average of the two for riftsawn. The coefficients hold for MC between about 6% and 14%.
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From climate — enter a humid and a dry season (indoor conditions where the piece will live). Each becomes an equilibrium moisture content (EMC) using Simpson’s sorption equation from the Wood Handbook (chapter 4), and the movement is the difference. If built at the midpoint, the piece moves about half that each way.
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From moisture content — enter two MC readings, for example a meter reading now and the expected service EMC.
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EMC table — the equilibrium MC for a grid of temperatures and humidities, nearest cell highlighted.
The guidance turns the movement into gaps and slots: panel clearance in frame grooves, elongated slots or clips for tabletops, and slotted breadboard pegs. Individual boards can move 25% more or less than the species average, and finishes slow moisture exchange but do not stop it.
Sharing
Share link copies a URL that opens this tool exactly as you have it set up. It carries the species, width, cut and climate settings. Opening a link replaces your own saved settings for the tool; a Restore my settings button brings them back. To write a link by hand, use species, width, cut, units — for example /tools/wood-movement/?species=Cherry.
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