Project Planning
Wood Movement Calculator (Seasonal)
Predict how much a solid wood panel will expand or contract across seasons — across the grain, not along it.
Calculator
Tangential / Radial / Longitudinal
What makes this different
Most calculators give a single number from a tangential coefficient. This one computes tangential vs radial movement separately, lets you input the actual MC swing in your shop, and shows the dimensional change per foot of width for the worst-case orientation (flat-sawn, which moves the most).
Who it's for & when to use it
Sizing table top glue-ups; designing raised-panel cabinet doors; planning breadboard ends.
How to use
- Enter the dimensions of your material or the parameters of your project.
- Adjust the optional knobs (waste factor, kerf, planer allowance) to match your shop practice.
- Click Calculate and read the output. Use the per-item breakdown for ordering, the totals for budgeting.
- Compare the result to your lumber yard's quote — the effective $/BF column is the apples-to-apples number.
Formula: Movement = width × tangential_coeff × (MC_high − MC_low) / 100. Tangential ≈ 0.025, radial ≈ 0.015, longitudinal ≈ 0.001.
Notes & tips from the shop
- Flat-sawn boards (tangential) move twice as much across the grain as quarter-sawn (radial). Choose cuts deliberately for stable panels.
- Plywood and MDF move negligibly with humidity — that's why they're used for cabinet boxes and doors in unstable climates.
- Breadboard ends must allow the top to slide; never glue them along the long grain.
Frequently asked questions
Why is my table top cracking in winter?
The wood dried below the build MC and shrank. Build the top at the lowest expected MC, or use a stable panel construction.
Should I seal all sides equally?
Yes — slow finish penetration on one face causes cupping toward the dry side. Seal end grain especially.
How much movement is too much?
More than 1/16 in per foot of width needs an allowance. More than 1/8 in per foot calls for a different construction method (ply, frame-and-panel).
Limitations
Single panel. Frame-and-panel construction and plywood substrates need different analysis.
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