Wood Movement Calculator
Estimate how much a panel will expand or contract across the grain from seasonal moisture change, by species and grain orientation, so your designs leave the right amount of room.
Width across the grain. Length barely moves.
Indoor wood typically swings 6 to 12 percent through the year.
Expected movement
0.531 in
In sixteenths
8.5 /16 in
A 24 in wide flatsawn Red Oak panel moving from 6 to 12 percent moisture content changes about 0.531 in across the grain. Leave at least that much room in frames, breadboards, and tabletop fasteners.
How the math works
Movement equals width times the species' dimensional change coefficient times the change in moisture content percentage. The coefficients come from the US Forest Products Laboratory and differ for tangential (flatsawn) and radial (quartersawn) directions.
The result is an estimate, since coefficients vary board to board, but it reliably tells you whether a design needs an eighth of an inch of room or over half an inch, which is the difference between a floating panel that survives and one that splits.
FAQ
- How much does wood move seasonally?
- A 24 inch wide flatsawn red oak panel moving between 6 and 12 percent moisture content changes about 0.53 inches, over half an inch. Quartersawn stock of the same species moves less than half that, which is why grain orientation matters as much as species.
- Does wood move along its length?
- Barely. Longitudinal movement is roughly one tenth of one percent and is ignored in furniture design. Movement across the grain, tangentially and radially, is what cracks panels and jams drawers.
- What moisture content range should I design for?
- Indoor furniture in most climates cycles between about 6 percent in winter (heated, dry air) and 10 to 12 percent in humid summers. Use your local extremes; a moisture meter on scrap stored in the room tells you where you are today.