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Shrinkage PredictorWood Dimensional Movement Calculator

Predict exactly how much wood will shrink or swell when its moisture content changes. Calculate radial, tangential and volumetric movement for precise allowances in furniture, flooring and joinery.

Radial + TangentialVolumetric ShrinkagePer-Species CoefficientsT/R Ratio Warp RiskPDF Report
SHR

Shrinkage Predictor

Wood Dimensional Movement Calculator

Wood and Dimensions

Sets shrinkage coefficients automatically.

mm
mm
Moisture Content Change
%

Current moisture content.

%

Target / service moisture content.

% total

Green to oven-dry. Auto-set by species.

% total

Green to oven-dry. Auto-set by species.

% MC

No shrinkage above this MC.

OK
Shrinkage Prediction Results
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mm
Width Change
-
mm
Thickness Change
-
%
Volumetric Change
-
T/R ratio
Warp Risk
DimensionOriginalFinalChange% Change
Shrinkage Calculation
About Shrinkage Predictor
Wood shrinks as it loses moisture below the Fiber Saturation Point (about 28% MC) and swells as it gains moisture. Shrinkage is not equal in all directions: tangential movement (along growth rings) is typically about twice the radial movement (across rings). This difference causes cupping, warping and checking. This tool predicts the exact dimensional change so you can build in proper allowances.
Where Is This Used?
Furniture DesignWide Panel Glue-upsFlooring GapsDoor + Window JoineryDrawer FittingExport Furniture QC
Formulas Used
MC change below FSP: dMC = (MC_start - MC_final), capped at FSPShrinkage % = S_total x (dMC_below_fsp / FSP)where S_total = radial or tangential total shrinkage coefficientDimension change = Original x (Shrinkage% / 100)Volumetric ~ Radial% + Tangential% (small-strain approximation)T/R ratio = Tangential / Radial (warp risk: under 1.5 stable, over 2.0 high)
Frequently Asked Questions
Why does flat-sawn wood cup but quarter-sawn stays flat?
Flat-sawn boards show tangential movement across their width (the larger shrinkage), while quarter-sawn boards show radial movement across their width (the smaller, more uniform shrinkage). This is why quarter-sawn is preferred for stable applications like flooring and instrument tops.
What is the T/R ratio and why does it matter?
The tangential-to-radial shrinkage ratio predicts warping tendency. A ratio under 1.5 means the wood moves evenly and stays flat. A ratio above 2.0 (like Beech at ~2.0) means high distortion risk - boards will cup and twist unless carefully dried and oriented.
How much gap should I leave for a wooden floor?
Calculate the seasonal MC swing for your region (use the EMC Calculator), then run that MC range through this tool for your board width. The width change is the expansion gap you must leave at walls. In monsoon India this can be 8-12mm across a room.
ResourcesView the formulasWood Species DatabaseFormula Library
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EMC CalculatorEquilibrium moisture content from temp and humidityGreen Weight CalculatorWeight of green timber by volume and speciesKiln Schedule FinderDrying time and temperature scheduleFiber Saturation CalculatorFind the fiber saturation point of a species