Wood Movement Calculator
Wood moves across the grain as humidity changes. Enter your board's dimensions, species-based movement coefficient, and expected humidity swing to estimate how much to allow for expansion or contraction in your design.
About this calculator
Estimate how much a wood panel or board will expand or shrink across its width due to seasonal humidity changes, based on species movement coefficients.
Frequently Asked Questions
Why does wood move across its width but not its length?
Wood is roughly 10-15 times more dimensionally stable along the grain (length) than across it (width), so nearly all seasonal movement occurs across the width and thickness.
How do I find my species' movement coefficient?
Published wood movement tables (like those from the Forest Products Laboratory) list tangential and radial shrinkage values per species; this calculator uses simplified categories for quick estimates.
Why does this matter for furniture design?
Panels glued rigidly on all sides can crack or buckle as they try to expand/contract. Allowing for movement with breadboard ends, floating panels, or slotted screw holes prevents this.