Wood Movement Calculator
How much will that panel move? Estimate seasonal expansion and contraction by species, grain orientation, and moisture content change.
Wood moves. Every species moves a different amount, and flat-sawn boards move roughly twice as much as quarter-sawn ones. Getting this wrong means cracked panels, blown-open joints, or a tabletop that's cupped by spring.
Enter your board width, species, and the moisture content range your shop and home are likely to see. The calculator uses dimensional change coefficients from the USDA Wood Handbook.
Wood MovementW × ΔMC × C
Board will expand by
0.266in
6.748 mm · ΔMC = 6.0%
The formula
Movement = Width × ΔMC × C, where Width is in inches, ΔMC is the change in moisture content in percentage points, and C is the species-specific dimensional change coefficient.
Flat-sawn boards use the tangential coefficient; quarter-sawn boards use the radial coefficient. Tangential movement is typically 1.5–2× greater, which is why quarter-sawing is worth the cost for wide panels.
Typical moisture content ranges
| Condition | MC range |
|---|---|
| Kiln-dried lumber | 6–8% |
| Heated home, winter | 5–8% |
| Conditioned shop | 7–10% |
| Unheated shop or garage | 10–15% |
| Outdoor / covered porch | 12–18% |
Rules of thumb
- 1% MC ≈ 1/32″ per foot of width for flat-sawn hardwoods — a rough sanity check for any result.
- Allow for movement in panel designs. Float panels in frames; don't glue edge-to-edge joints across the grain on wide slabs.
- Acclimate your stock. Bring lumber into your shop for at least a week before milling. A moisture meter tells you where it actually is — and it will not be where you expected.
- Quarter-sawn is more stable — roughly half the movement of flat-sawn — and worth considering for tabletops, doors, and instrument soundboards.
Useful gear
- Moisture meter — know your MC before you mill, not after
- Shop hygrometer — track humidity year-round so seasonal movement is never a surprise
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