Wood Shrinkage Calculator for boards and framing. Enter species, ring angle, size and moisture now and later to see the final size, or open the framing tab for the drop each story.
Read the end grain for the ring angle. Flat rings mean flatsawn, rings standing upright mean quartersawn.
Wall and Floor Build
Count only wood lying flat in the load path. Engineered I-joists and LVL rims are made dry, so they are usually left out.
Units and Method
Fiber saturation is where shrinking starts. The Wood Handbook uses 30% for most woods and 22% for cedars and redwood.
Size at Other Moisture Levels
Your later moisture is highlighted and the starting row is in italics. Nothing changes above fiber saturation.
| Moisture | Width | Thickness |
|---|---|---|
| 4% | 7.075 in | 0.742 in |
| 6% | 7.119 in | 0.744 in |
| 8% | 7.162 in | 0.746 in |
| 10% | 7.206 in | 0.748 in |
| 12% | 7.250 in | 0.750 in |
| 14% | 7.294 in | 0.752 in |
| 16% | 7.338 in | 0.754 in |
| 19% | 7.403 in | 0.757 in |
| 22% | 7.469 in | 0.760 in |
| 25% | 7.535 in | 0.763 in |
| 30% and up | 7.644 in | 0.768 in |
Same Board in Other Species
Green-to-ovendry shrinkage from Wood Handbook Tables 4-3 and 4-4, sorted from most stable to least for your width, grain and moisture change.
| Species | Tangential | Radial | Width Change |
|---|---|---|---|
| Sassafras | 6.2% | 4.0% | 0.062 in |
| Butternut | 6.4% | 3.4% | 0.064 in |
| Aspen, quaking | 6.7% | 3.5% | 0.067 in |
| Cherry, black | 7.1% | 3.7% | 0.072 in |
| Maple, bigleaf | 7.1% | 3.7% | 0.072 in |
| Locust, black | 7.2% | 4.6% | 0.073 in |
| Alder, red | 7.3% | 4.4% | 0.074 in |
| Ash, white | 7.8% | 4.9% | 0.079 in |
| Walnut, black | 7.8% | 5.5% | 0.079 in |
| Maple, red (soft) | 8.2% | 4.0% | 0.083 in |
| Yellow-poplar | 8.2% | 4.6% | 0.083 in |
| Sycamore, American | 8.4% | 5.0% | 0.086 in |
| Oak, northern red | 8.6% | 4.0% | 0.088 in |
| Hickory, pecan | 8.9% | 4.9% | 0.091 in |
| Cottonwood, eastern | 9.2% | 3.9% | 0.094 in |
| Basswood, American | 9.3% | 6.6% | 0.095 in |
| Birch, yellow | 9.5% | 7.3% | 0.097 in |
| Elm, American | 9.5% | 4.2% | 0.097 in |
| Oak, live | 9.5% | 6.6% | 0.097 in |
| Maple, sugar (hard) | 9.9% | 4.8% | 0.102 in |
| Sweetgum | 10.2% | 5.3% | 0.105 in |
| Hickory, shagbark | 10.5% | 7.0% | 0.108 in |
| Oak, white | 10.5% | 5.6% | 0.108 in |
| Oak, southern red | 11.3% | 4.7% | 0.117 in |
| Beech, American | 11.9% | 5.5% | 0.124 in |
Shrinkage by Level
Each level adds its plates and the floor framing it carries. The drop builds up level by level toward the roof.
| Level | Counted | Depth | Drop | Total |
|---|---|---|---|---|
| 1 | Plates | 4.50 in | 0.067 in | 0.067 in |
| 2 | Floor, plates | 15.75 in | 0.233 in | 0.300 in |
| 3 | Floor, plates | 15.75 in | 0.233 in | 0.533 in |
Wood Shrinkage Calculator for Boards and Framing
People search for wood shrinkage for two different jobs. A woodworker wants to know how much a board or glued panel will lose between two moisture readings. A builder or engineer wants to know how far a multi-story wood frame will settle as its plates and joists dry. The Wood Shrinkage Calculator handles both, on the Board or Panel tab and the Framing Stack tab.
On the board tab, pick the species, enter the growth ring angle, the actual width and thickness in inches, and the moisture content now and later. Sizes are actual measured sizes, not nominal. A 1x8 is entered as 7.25 inches. The results give the new width and thickness, the change per 1% of moisture and the same board at other ring angles.
Shrinkage Between Two Moisture Readings
The tool uses the green-basis equation from Chapter 13 of the 2021 Wood Handbook, which works for any change below fiber saturation.
DI is the starting size, MI and MF are the starting and ending moisture, and S is the species' total shrinkage from green to oven dry. FSP is the fiber saturation point, 30% for most species. The handbook uses 22% for western redcedar, northern white cedar and redwood, and the tool switches automatically when you pick one.
Above fiber saturation the board does not change size, so any reading above it counts as the fiber saturation point. With the defaults, a 7.25 inch flatsawn northern red oak board going from 12% to 8% loses 0.088 inch and ends at 7.162 inches. Its 3/4 inch thickness loses only 0.004 inch.
Between 6% and 14% moisture the Wood Handbook also gives a simple coefficient, 0.00304 per 1% moisture for flatsawn northern red oak. It gives the same 0.088 inch here, and the tool's alert shows both coefficients when your readings fall in that range.
Some older guides use the shortcut of size times shrinkage times moisture change divided by the fiber saturation point. For the same board it gives 0.083 inch. The Wood Handbook notes this straight-line method underestimates the true change by about 5%.
Growth Ring Angle, Not Just Flat or Quarter
Most shrinkage calculators offer only flatsawn or quartersawn. Real boards often have rings at an angle, so the tool takes the angle between the rings and the face, from 0° for flatsawn to 90° for quartersawn.
These equations from Comstock (1965) are the ones the Forest Products Laboratory uses in Research Paper FPL-RP-489. ST and SR are the tangential and radial shrinkage, and θ is the ring angle.
For the default board, width shrinkage drops from 0.088 inch flatsawn to 0.063 inch at 45° and 0.040 inch quartersawn. Thickness moves the other way, so a quartersawn board changes more in thickness. Red oak's tangential to radial ratio of 2.15 sets how big that gap is.
Rings at an angle also shrink unevenly across the diagonals, so square stock turns slightly diamond-shaped. The fourth card gives how far out of square the piece goes and the difference between its diagonals. At 0°, it notes the flatsawn board will cup away from the pith instead.
Cutting Parts Now for the Size You Want Later
Set Sizes Entered Are to Wanted Later and the tool works backward. Enter the finished size you need and it gives the size to rip or plane now.
To end at 7.25 inches once red oak drops from 12% to 8%, rip it at 7.339 inches. This helps when milling parts from air-dried stock that will dry further in a heated house.
The Board-to-Board Range row adds a 15% band either side of the result. That band is the tool's planning margin, not a published figure. A 1957 FPL article on shrinkage notes that species shrinkage values apply to large numbers of boards rather than to any single board.
For seasonal movement in a finished piece, and the gaps and fastener slots it needs, use the Wood Movement Gap Calculator. For green bowl blanks and saw allowances above 30% moisture, the Green Wood Shrinkage Calculator goes further.
Framing Shrinkage in Multi-Story Buildings
The Framing Stack tab estimates how far each floor of a wood-framed building settles as its lumber dries to service moisture. WoodWorks explains in Accommodating Shrinkage in Multi-Story Wood-Frame Structures that the shrinkage comes from wood lying flat, such as plates, floor joists and rims. Studs barely change length.
The same paper puts light-frame shrinkage at 0.05 to 0.5 inch per level. It notes that Section 2304.3.3 of the 2018 International Building Code requires a shrinkage analysis when wood walls carry more than two floors and a roof.
Because ring orientation in plates and joists is unknown, WoodWorks either averages tangential and radial shrinkage or takes all tangential as the worst case. The tool offers both. It also shows WoodWorks' quick rule of 0.0025 inch per inch of cross-grain wood per 1% moisture.
The defaults are three stories of coast Douglas-fir on a slab, with 2x12 floors, a single sole plate and a double top plate. Framed at 19% and settling at 12%, each upper level carries 15.75 inches of cross-grain wood and drops 0.233 inch. The level 3 top plate ends up 0.533 inch lower.
The quick rule gives 0.63 inch for the same stack and the all-tangential case 0.657. Hanging the upper floor joists from the walls cuts the total to 0.200 inch, since only plates stay in the load path. Framing with KD-15 lumber instead of 19% stock cuts it to 0.230 inch.
Engineered I-joists and LVL rims are made dry, and WoodWorks notes many engineers leave them out of the count. Choose Engineered, Not Counted for the floor depth to model that.
WoodWorks advises planning slip joints at plumbing risers and gaps at brick veneer and masonry shafts, which do not shrink with the wood. A compressible filler in a veneer gap usually squeezes to only half its thickness, so the gap should be twice the expected movement.
When Framing Is Dry Enough to Finish
What moisture should framing reach before drywall and trim go on?
The 2021 Wood Handbook says interior finish and trim can normally go on once headers and joists approach an average of about 12% moisture. It adds that if framing is no more than about 5% above its eventual service moisture when the wall finish goes on, shrinkage defects are unlikely to show.
Check headers, floor joists and ceiling joists with a meter before closing walls. The Framing Stack tab shows how much settlement is still to come between your reading and the service moisture you expect.