🪵 Wood Shrinkage Calculator
Calculate radial, tangential & volumetric shrinkage for any wood species and moisture content change
| Species | Radial %/% MC | Tangential %/% MC | Total Radial (green→dry) | Total Tang. (green→dry) | Volumetric % | Janka (lbf) |
|---|---|---|---|---|---|---|
| White Oak | 0.200 | 0.375 | 5.6% | 10.5% | 16.3% | 1360 |
| Red Oak | 0.179 | 0.369 | 4.0% | 8.6% | 13.7% | 1220 |
| Hard Maple | 0.171 | 0.353 | 4.8% | 9.9% | 14.7% | 1450 |
| Soft Maple | 0.143 | 0.275 | 3.7% | 7.1% | 11.6% | 950 |
| Black Walnut | 0.190 | 0.275 | 5.5% | 7.8% | 12.8% | 1010 |
| Black Cherry | 0.157 | 0.250 | 3.7% | 7.1% | 11.5% | 950 |
| White Ash | 0.179 | 0.329 | 4.9% | 7.8% | 13.3% | 1320 |
| Douglas Fir | 0.171 | 0.271 | 4.8% | 7.6% | 12.4% | 660 |
| White Pine (E) | 0.075 | 0.218 | 2.1% | 6.1% | 8.2% | 380 |
| W. Red Cedar | 0.089 | 0.214 | 2.4% | 5.0% | 6.8% | 350 |
| Teak | 0.111 | 0.186 | 2.6% | 5.3% | 7.2% | 1000 |
| Mahogany (H) | 0.111 | 0.186 | 3.0% | 5.1% | 8.5% | 800 |
| Yellow Birch | 0.214 | 0.325 | 7.3% | 9.5% | 16.8% | 1260 |
| Yellow Poplar | 0.154 | 0.254 | 4.6% | 8.2% | 12.7% | 540 |
| Location / Use | Typical RH % | EMC % | Recommended Final MC |
|---|---|---|---|
| Heated interior – dry climate | 25–30% | 5–6% | 6% |
| Heated interior – average | 40–50% | 7–9% | 8% |
| Heated interior – humid climate | 55–65% | 10–12% | 11% |
| Sheltered outdoor / porch | 65–75% | 12–14% | 13% |
| Exposed outdoor (coated) | 75–85% | 14–16% | 15% |
| Exposed outdoor (uncoated) | 80–90% | 16–19% | 18% |
| Project | Grain Orient. | Width | MC Change | Expected Shrinkage | Recommended Gap |
|---|---|---|---|---|---|
| Solid wood tabletop (oak) | Flatsawn | 30 in | 12→8% | ~3/8 in | 1/2 in expansion |
| Hardwood flooring (maple) | Quartersawn | 2.25 in | 12→7% | ~0.02 in/board | 1/16 in between boards |
| Cabinet door panel (cherry) | Flatsawn | 12 in | 12→8% | ~0.18 in | 3/16 in float in groove |
| Deck board (cedar) | Flatsawn | 5.5 in | 19→13% | ~0.10 in | 1/8 in spacing |
| Frame & panel door (pine) | Flatsawn | 8 in panel | 15→8% | ~0.14 in | 1/4 in float in groove |
| Butcher block top (maple) | Edge grain | 18 in | 12→8% | ~0.15 in | Allow movement, no glue edge |
Wood shrinks. That is simply the reality of working with it. Although you already cut it from tree, Wood never truly dies.
The cells inside it still live somehow react to changes in heat and humidity, so it will always expand and shrink during its life.
Why Wood Shrinks and How to Deal With It
When does the real shrink happen? Wood does not start shrinking until the water content falls under the so-called fiber saturation point, that is around 28 to 30 percent. Under that limit, the shrinking becomes very predictable, it follows a straight line as Wood loses more water.
Above that level? Wood stays stable and keeps its size unchanged.
Here it becomes interesting. Wood does not shrink evenly, as one would hope. On the contrary, it shrinks by direction, the angle of the grain, simply said.
Boards or floor beams lose size in their crossing, for instance in width and thickness. Lengthwise movement? That is almost impossible to measure, almost nothing, nothing to care about.
In the radial plane (from the center of tree out), one finds around 2 to 6 percent of shrinkage. In the tangential plane, that follows the year-rings, that almost doubles, about 5 to 10 perecnt.
Different species of Wood do not all act equally. Oak, beech and hickory shrink more strongly than pine, mesquite and cedar. If the water content stays steady, the shrinking will simply end.
Here is the basic law of the cause.
Green Wood has its biggest size, while kiln-dried Wood shows the smallest possible form. The difference between those two extremes shows the maximum percent of shrinkage (what we call total shrink). Most framing timber has around 19 percent of humidity, while Wood for furniture dries to between 6 and 8 percent.
Use Wood that is still too wet? That brings serious troubles later.
A panel from several bits, glued together, shrinks just like one broad board, if the grain goes the same direction. Use only radial grain instead of mixed or tangential to reduce the shrinkage a bit. Quarter-sawing helps too reduce movement, but kiln-drying…
Despite all its benefits, does not fully remove future motion.
Applying finish slows the absorption of humidity, although it does not halt it fully. Here is why traditional woodworkers trusted in floating panels and joints, they let Wood move without cracking or tearing of your projects. Moisture meters help to control the values before you start to build and dry out wet Wood fast, while one cuts problems of shrinkage down.
Predicting the shrinkage is not hard, once one has the right numbers or access to an online calculator. Planningfor movement early is always the wiser step.
