How it works
Wood takes on and gives up water with the seasons and changes dimension across the grain when it does. Along the grain it hardly moves. Flatsawn (tangential) movement is roughly twice quartersawn (radial) movement in most species.
Each species has a published shrinkage figure from green to oven-dry. The Wood Handbook treats the change as linear between oven-dry and the fiber saturation point, so multiply the width by the shrinkage, then by the share of that 30-point range your moisture change covers.
Worked example
A 12-inch-wide flatsawn white oak board moving from 8% to 12% moisture:
- White oak, flatsawn (tangential): S = 10.5% from green to oven-dry
- Change = 12 in × (10.5 ÷ 100) × (12 − 8) ÷ 30 = 0.168 in
- Final width = 12 + 0.168 = 12.168 in (1.4%)
| Input | Value |
|---|---|
| Species | White oak |
| Grain (measured across) | Flatsawn (tangential) |
| Board width | 12 in |
| Starting moisture content | 8 % |
| Ending moisture content | 12 % |
| Result | Value |
|---|---|
| Change in width | 0.168 in |
| Final width | 12.168 in |
| Percent change | 1.4 % |
Shrinkage by species
| Species | Tangential (%) | Radial (%) |
|---|---|---|
| White oak | 10.5 | 5.6 |
| Northern red oak | 8.6 | 4 |
| Bur oak | 8.8 | 4.4 |
| Sugar (hard) maple | 9.9 | 4.8 |
| Red maple | 8.2 | 4 |
| Silver maple | 7.2 | 3 |
| White ash | 7.8 | 4.9 |
| Green ash | 7.1 | 4.6 |
| Yellow birch | 9.5 | 7.3 |
| Paper birch | 8.6 | 6.3 |
| Black walnut | 7.8 | 5.5 |
| Black cherry | 7.1 | 3.7 |
| American elm | 9.5 | 4.2 |
| Hackberry | 8.9 | 4.8 |
| Shagbark hickory | 10.5 | 7 |
| Black locust | 7.2 | 4.6 |
| Quaking aspen | 6.7 | 3.5 |
| American basswood | 9.3 | 6.6 |
| Eastern cottonwood | 9.2 | 3.9 |
| Yellow-poplar | 8.2 | 4.6 |
| Eastern white pine | 6.1 | 2.1 |
| Red pine | 7.2 | 3.8 |
| Tamarack | 7.4 | 3.7 |
| Douglas-fir (coast) | 7.6 | 4.8 |
| Western redcedar | 5 | 2.4 |
| Balsam fir | 6.9 | 2.9 |
Show the shrinkage by species table
| Species | Tangential (%) | Radial (%) |
|---|---|---|
| White oak | 10.5 | 5.6 |
| Northern red oak | 8.6 | 4 |
| Bur oak | 8.8 | 4.4 |
| Sugar (hard) maple | 9.9 | 4.8 |
| Red maple | 8.2 | 4 |
| Silver maple | 7.2 | 3 |
| White ash | 7.8 | 4.9 |
| Green ash | 7.1 | 4.6 |
| Yellow birch | 9.5 | 7.3 |
| Paper birch | 8.6 | 6.3 |
| Black walnut | 7.8 | 5.5 |
| Black cherry | 7.1 | 3.7 |
| American elm | 9.5 | 4.2 |
| Hackberry | 8.9 | 4.8 |
| Shagbark hickory | 10.5 | 7 |
| Black locust | 7.2 | 4.6 |
| Quaking aspen | 6.7 | 3.5 |
| American basswood | 9.3 | 6.6 |
| Eastern cottonwood | 9.2 | 3.9 |
| Yellow-poplar | 8.2 | 4.6 |
| Eastern white pine | 6.1 | 2.1 |
| Red pine | 7.2 | 3.8 |
| Tamarack | 7.4 | 3.7 |
| Douglas-fir (coast) | 7.6 | 4.8 |
| Western redcedar | 5 | 2.4 |
| Balsam fir | 6.9 | 2.9 |
Shrinkage from green to oven-dry as a percentage of the green dimension, USDA Wood Handbook Table 4-3.
Assumptions and limits
- Shrinkage is linear in moisture content between 0% and 30%, and 30% is used as the fiber saturation point. The Handbook recommends both when the exact figure is unknown.
- Shrinkage percentages are of the green dimension, so results are slightly conservative for wood already dried.
- Board grain is measured across the width. Real boards have mixed ring angles; use the flatsawn value when unsure.
- Interior equilibrium moisture in the upper Midwest swings roughly from 5–6% in winter heat to 11–12% in humid summer; use your own readings if you have them.
Common questions
How much gap should I leave in a solid wood tabletop?
Run the calculator across the widest moisture swing for your climate, then design the fasteners (figure-8s, buttons, slotted holes) to allow at least that much movement across the width.
Does wood move in length?
Barely. Movement along the grain is roughly 0.1–0.2%, so furniture design ignores it.
Which woods move the least?
Quartersawn stock of stable species such as eastern white pine and western redcedar. Flatsawn white oak, hickory, and maple are the most active.
Sources
- USDA Forest Products Laboratory, Wood Handbook: Wood as an Engineering Material (FPL-GTR-282, 2021): Table 4-3 (shrinkage green to oven-dry) and the dimensional-change method in Chapter 4, which uses 30% MC as the fiber saturation point when it is not known.
- Read them: USDA Wood Handbook, Chapter 4 (shrinkage)
Updated 2026-09-30