Calculator
Wood movement calculator
Wood shrinks and swells across its width as its moisture content changes with the seasons. Pick a species, board width, and how it was sawn to estimate how much it will move.
Your board
JavaScript is off, so this page cannot do the math for you. Use the formula and the species table below, or turn JavaScript on for a live result.
Indoor furniture in much of the US runs very roughly 6–8% in a heated winter and 10–12% in a humid summer. A moisture meter gives you a real number.
Expected movement —
Width afterward —
Coefficient used: —
The Handbook coefficients are for changes between about 6% and 14% moisture content. Outside that range, treat this as a rough estimate.
Enter a width greater than zero and moisture contents from 0 to 30%.
The formula
Change in width = width × coefficient × (moisture content later − moisture content now). Use the tangential coefficient for flat-sawn boards and the radial coefficient for quartersawn boards. A negative result means the board shrinks.
Worked example
A 12″ wide flat-sawn red oak tabletop board going from 6% to 12% moisture content: 12 × 0.00369 × 6 ≈ 0.27″, a little over ¼″. Quartersawn, the same board moves about 12 × 0.00158 × 6 ≈ 0.11″.
Designing for movement
Let solid-wood panels float in grooves, attach tabletops with buttons or figure-8 fasteners, and use slotted holes for screws that cross the grain. Size panels for the season: leave room for swelling if you build in dry winter air.
Species coefficients
| Species | Radial (quartersawn) | Tangential (flat-sawn) |
|---|---|---|
| Red oak (commercial) | 0.00158 | 0.00369 |
| White oak (commercial) | 0.0018 | 0.00365 |
| Hard maple (sugar) | 0.00165 | 0.00353 |
| Soft maple (red) | 0.00137 | 0.00289 |
| Black cherry | 0.00126 | 0.00248 |
| Black walnut | 0.0019 | 0.00274 |
| White ash | 0.00169 | 0.00274 |
| Yellow-poplar | 0.00158 | 0.00289 |
| American beech | 0.0019 | 0.00431 |
| Yellow birch | 0.00256 | 0.00338 |
| Basswood | 0.0023 | 0.0033 |
| Eastern white pine | 0.00071 | 0.00212 |
| Douglas-fir (coast) | 0.00165 | 0.00267 |
| Western redcedar | 0.00111 | 0.00234 |
Source
Coefficients are the dimensional change coefficients for shrinking or swelling within 6% to 14% moisture content, from Table 13–5 of the Wood Handbook: Wood as an Engineering Material (General Technical Report FPL–GTR–190, 2010), Forest Products Laboratory, USDA Forest Service.
Wood Handbook, chapter 13 (PDF, USDA Forest Service) (external site, opens in a new tab)
Results are estimates, not guarantees. Individual boards vary a lot, even within one species, and the Handbook coefficients are averages. Finishes slow moisture exchange but do not stop it. Leave extra room in your design.
This calculator runs in your browser only. Your numbers aren't sent to us or anyone else, and the calculator doesn't save them. The page itself uses analytics; see our privacy policy.
Related on this site
We pick tools from independent tests and reviews, not our own testing.