Wood Shrinkage Calculator
Wood Doesn't Shrink the Same Amount in Every Direction
As wood loses moisture below the fiber saturation point, it shrinks — but not uniformly. Shrinkage along the grain (longitudinally) is negligible, while shrinkage across the growth rings (tangentially) is roughly double the shrinkage across the rings' radius (radially), and the exact percentages vary meaningfully by species. That difference is why flatsawn boards cup and quartersawn boards stay flatter as humidity changes.
The Formula
Effective Shrinkage % = Published Full Shrinkage % × (Moisture Change % ÷ 100)
The published shrinkage percentages represent the full green-to-oven-dry range for each species and grain direction. Since real projects rarely dry all the way to oven-dry, the moisture change percentage scales that full-range figure down to the portion of drying actually being modeled.
Published Shrinkage Values by Species
| Species | Tangential | Radial |
|---|---|---|
| White Oak | 10.5% | 5.6% |
| Hard Maple (Sugar Maple) | 9.9% | 4.8% |
| Red Oak | 8.6% | 4.0% |
| Yellow Poplar | 8.2% | 4.6% |
| Black Walnut | 7.8% | 5.5% |
| Southern Yellow Pine | 7.6% | 5.1% |
| Douglas Fir | 7.5% | 4.8% |
| Black Cherry | 7.1% | 3.7% |
| Honduras Mahogany | 5.1% | 3.1% |
| Western Red Cedar | 5.0% | 2.4% |
Worked Example
| Grain direction | Dimensional change | Final dimension |
|---|---|---|
| Tangential | 0.52 in | 5.48 in |
| Radial | 0.24 in | 5.76 in |
The same board loses more than double the width across the tangential direction compared to the radial direction — a difference significant enough to affect how a flatsawn versus quartersawn cut of the same board behaves.
Where This Matters
- Sizing panels that need to fit a frame — a panel cut to exact dimension while still slightly above target moisture content will shrink after the fact, so accounting for expected shrinkage keeps the final fit correct.
- Choosing quartersawn stock for stability — because radial shrinkage is consistently lower than tangential across species, quartersawn lumber is preferred for parts that need to stay dimensionally stable, like tabletops and door panels.
- Predicting seasonal movement — furniture that will experience real seasonal humidity swings (not full oven-dry conditions) needs the moisture-change percentage scaled down from 100% to reflect that smaller, ongoing movement.
How to Use This Calculator
- Select the wood Species.
- Select the Grain Direction: Tangential or Radial.
- Enter the Original Dimension in inches.
- Enter the % of Full Green-to-Dry Range being modeled (optional, defaults to 100).
- Select Calculate to see the dimensional change and final dimension.
Related Calculations
Check the moisture content driving this shrinkage with the Wood Moisture Content Calculator, or see how species choice affects joint strength with the Wood Joint Strength Calculator.