How much does wood move with humidity changes?

Wood movement depends on species, grain orientation, and moisture content change. A 200mm wide flat-sawn oak board can move about 2.8mm between summer and winter humidity extremes. Quarter-sawn boards move roughly half as much. This calculator gives exact figures.

What moisture content should I aim for?

In the UK, indoor furniture should be at 8-10% moisture content. Wood for unheated spaces should be 12-14%. Outdoor wood stabilises around 16-20%. Allow wood to acclimatise in its final environment for at least 2 weeks before working it.

What is the difference between flat-sawn and quarter-sawn movement?

Flat-sawn (tangential) boards move roughly twice as much as quarter-sawn (radial) boards across their width. Quarter-sawn is more stable because the growth rings run perpendicular to the board face. This is why quarter-sawn is preferred for table tops and wide panels.

How do I allow for wood movement in a table top?

Attach the top using elongated screw holes, figure-of-eight clips, or Z-clips that allow the top to expand and contract freely. Never glue a solid top to the apron. Leave 2-3mm expansion gaps at any constraint point. This calculator tells you exactly how much movement to expect.

Does plywood expand and contract?

Plywood is dimensionally stable because the alternating grain directions cancel out most movement. It expands less than 0.1% in either direction. MDF is similarly stable. This is why plywood and MDF are preferred for dimensionally critical applications like jigs and templates.

WoodCalcs

Wood Expansion Calculator — Seasonal Movement

Calculate seasonal wood movement for proper gap allowances in furniture and flooring.

Wood Species

Grain Orientation

Board Width

Across the grain

Initial Moisture Content

Final Moisture Content

How We Calculate This

This calculator estimates dimensional change in solid wood due to moisture content changes.

The formula

Movement = Board width x Coefficient x MC change / 100

The coefficient depends on species and grain orientation. Tangential (flat-sawn) coefficients are roughly double the radial (quarter-sawn) values. Wood moves most across the grain and negligibly along the grain (typically less than 0.1%).

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.