Wood Movement Calculator
Wood movement is across-grain shrinkage or swelling from moisture-content change. The working calculator uses width, MC change, species shrinkage values, grain orientation and fiber saturation point.
Movement equation
Below fiber saturation, the calculator treats width change as a share of total shrinkage over the moisture-content change.
dW = W0 * S * (MC2 - MC1) / FSP
Grain orientation
Flat-sawn boards usually use tangential shrinkage; quarter-sawn boards usually use radial shrinkage. Mixed grain is only an approximation.
Fit allowance
Use measured material data for important fits. Panels, glue-ups, finish, restraint, grain angle and seasonal equilibrium moisture can change the real clearance needed.
Frequently asked questions
Is wood movement the same as wood shrinkage?
Shrinkage is movement in the drying direction. Swelling is movement in the wetting direction. The calculator reports signed width change.
Does wood move along the grain?
Longitudinal movement is usually much smaller and is not modeled here. This calculator focuses on across-grain movement.
Related pages
- Wood shrinkage calculator - working movement and final-width calculator.
- Wood moisture content calculator - oven-dry MC calculation before movement checks.
- Lumber weight calculator - wood weight and board-foot context.
- Board feet calculator - lumber volume and cost estimate.
- Shelf sag calculator - separate stiffness screen after movement allowances.