Predict how much your timber will expand or contract across a moisture range — before you glue up a panel or fit a drawer.
Dimensional change across a moisture range
Enter values above to calculate movement.
North American species: USDA Wood Handbook. Australian species: Forest & Wood Products Australia / Bootle Wood in Australia. European, African and Asian species: Hoadley Understanding Wood and published research. All values approximate — expect ±10–20% variation between individual boards.
All timber expands and contracts as its moisture content changes with the seasons. A flat-sawn white oak panel 200mm wide can move 4–5mm across a typical Sydney winter-to-summer humidity swing — enough to crack a glued-up panel, bind a drawer shut, or open a visible gap at a joint if you haven't designed for it.
The underlying calculation: dimensional change = board width × species coefficient × change in moisture content. The coefficient varies by species and grain orientation — flat-sawn uses the tangential coefficient (more movement), quarter-sawn the radial (less).
A seasonal swing of 5–7% moisture content is normal for furniture in a Sydney home. Designing for movement — elongated screw holes, floating panels, wood movement buttons on tabletops — is the difference between a piece that lasts decades and one that fails in its first summer.
The web calculator is great for the workshop. A mobile app version is on the way — it'll work offline, so you can run the numbers while standing in front of a stack of boards with no signal.
Want to know when it launches? Email me and I'll let you know.
I run beginner-friendly one-day workshops in Sydney. You'll use real tools, learn from a third-generation woodworker, and take home something you made yourself — no experience needed.
See upcoming workshops