Movement Calculator

Estimate across-grain width change from a moisture swing. Use this to choose clearances and avoid rigid cross-grain fixings.

Back to tools Browse species Enquire

Inputs

Enter your board or panel details.

This is a quick estimate for width change across the grain. Use it to choose clearances, joint details, and fixing methods.

Width

Start moisture

Target moisture

Species data

Choose a library species to load its movement values, or keep the manual value below.

Cut direction (simple)

Total shrinkage (green → oven dry)

If you do not know this, 8% tangential / 4% radial is a reasonable starting point for many furniture-sized decisions. Use species data where available.

Result

Estimated width change

Predicted dimensional change

—

Enter values to calculate.

Starting width —

Final width —

Change per side (if centred) —

Species coefficient —

Moisture change —

—

Explanation

What this estimate means

This uses total shrinkage (green → oven dry) spread across the fibre saturation range (roughly 30% moisture content down to 0%).

It assumes movement is roughly proportional to moisture change below fibre saturation. Real movement varies with species, grain, board position, and environment — treat the result as an allowance, not a guarantee.

Quick start

Measure the width across the grain (that’s the direction that moves).
Use a realistic moisture swing (seasonal change, indoors vs outdoors).
Choose a library species or enter a shrinkage value and select the cut direction.
Use the output to set clearances, joint details, and fixing methods.

Get better results

When in doubt, use tangential for wide panels; it is the safer allowance.
Movement is not a defect — design to accommodate it rather than trying to prevent it.
For very wide panels, build movement into the joinery (slots, buttons, figure-8s, or floating panels).
Confirm the species sheet if the project is outdoors or critical fit matters.

Next step

If you share the width and environment, I can suggest practical clearances and fixing details for your specific job.

Send an enquiry

Learn and verify

Browse guides Plain-English modules Open glossary Fast definitions Species reference sheets Behaviour and constraints

Assumptions

Treat the output as an allowance. Real movement varies by species, cut, board position, and indoor humidity. For wide panels, use the tangential option unless you know the board is reliably quarter-sawn.