Enter the wood species, (it's green to ovendry shrinkage
data will be automatically presented.
Select the calculation basis as either Relative Humidity OR Moisture Content.
Enter the settings and initial dimension.
Press the Compute button
Some Handy Numbers:
Typical moisture content of kiln-dried lumber:
7% to 10%
Typical moisture content of air-dried lumber:
14% to 19%
Average fiber saturation point:
Typical seasonal moisture content fluctuation of
unfinished wood (N. America):
4% to 14%
Average radial shrinkage, green to ovendry:
Average tangential shrinkage, green to ovendry:
Dimensions: The calculator assumes no specific
dimensional units such as inches or centimeters - if your input
dimensions represent inches, the output dimensions will also represent
inches. Dimensions with a fractional component may be specified as a
standard fraction or as a decimal value. Example: 24 3/4 or 24.75.
Moisture content: The moisture content of wood is
affected by the temperature and relative humidity of the environment in
which the wood is stored. For unfinished, kiln-dried wood stored
indoors, its moisture content will fluctuate seasonally from about 4% to
14% for most parts of North America. Valid range: 0 to 40.
Relative Humidity: The relative humidity option is
useful if you don't have a moisture meter to measure the wood's moisture
content directly but you are able to measure the relative humidity of
your shop. The wood's moisture content will be calculated using the
specified relative humidity and an assumed shop temperature of 70
degrees Fahrenheit. Your wood must have reached equilibrium at this
humidity for the calculator to work properly. Valid
range: 0 to 100.
Fiber saturation point (FSP): This is the moisture
content at which the wood's cell cavities are emptied of free water but
the cell walls are still fully saturated. As the wood dries and its
moisture content drops below the FSP, it will shrink and increase in
strength. The FSP differs for each species, ranging from about 22% to
35%, with an average of around 28%. Valid range: 20 to 40.
Shrinkage green to ovendry: laboratory tests
have been conducted for most commercial woods to measure how much the
wood shrinks from the green to the ovendry condition. In this context,
"green" refers to wood at or above the fiber saturation point. Shrinkage
is greatest in the tangential direction (along the growth rings),
ranging from about 6% to 12% with an average of 8%. Shrinkage in the
radial direction (perpendicular to the growth rings) ranges from about
3% to 5% with an average of 4%. Shrinkage in the longitudinal direction
is minimal, only about 0.1 %, and can generally be ignored for most
Keep in mind that the green to ovendry shrinkage values are maximum shrinkage values; kiln-dried wood that is stored
indoors will only shrink perhaps one-fourth to one-half of the maximum
Forest Products Laboratory. 1999. Wood Handbook - Wood as an
Engineering Material. Gen. Tech. Rep. FPL-GTR-113. U.S. Department
of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI.
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