Wood Shrinkage Calculator

This calculator computes the shrinkage of wood given its species and initial and final moisture content. Units are in the imperial system. 
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CalculationInputs﻿﻿Species
:Ash, Green​
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﻿﻿Shrinkage direction
:Radial​
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﻿﻿MC_initial
:0.2​
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﻿﻿MC_ult
:0.3​
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﻿﻿L_initial
:3in​
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Outputs﻿﻿S0
:4.6%​
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﻿﻿ΔS
:0.015333333333333319​
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﻿﻿ΔL
:0.05​
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﻿﻿L_ult
:3.05​
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Where:
﻿﻿MCinitial​
 is the wood's moisture content in it's initial condition, as a percentage ﻿(%)
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﻿﻿MCult​
 is the wood's moisture content in it's final condition, as a percentage ﻿(%)
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﻿﻿Linitial​
 is the wood's length in it's initial condition, taken in inches ﻿(in)
 if radial or tangential shrinkage direction is selected or in cubic inches ﻿(in3)
 if volumetric shrinkage direction is selected.
﻿﻿S0​
 is the oven-dry moisture content as a percentage of it's green state moisture content (%)
﻿﻿ΔS=S0​(MCFSP​MCultimate​−MCinitial​​)
 is the percent shrinkage from initial MC to ultimate MC ﻿(%)
. The fibre saturation state, ﻿MCFSP​
 is taken as 30% in this calculator.
﻿﻿ΔL=Linitial​×ΔS
 is the change in dimensions from initial MC to ultimate MC, taken in inches ﻿(in)
 if radial or tangential shrinkage direction is selected or in cubic inches ﻿(in3)
 if volumetric shrinkage direction is selected.
﻿﻿Lult​=Linitial​+ΔL
 final size of the specimen, taken in inches ﻿(in)
 if radial or tangential shrinkage direction is selected or in cubic inches ﻿(in3)
 if volumetric shrinkage direction is selected.
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ExplanationVariations in moisture content (MC) can cause wood to change dimensions, swelling as MC increases and shrinking as it decreases. However, these changes occur only when the wood is not fully saturated, meaning MC is below the fiber saturation point (FSP).
👉Quick note on the Fiber Saturation Point (FSP)
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The longitudinal shrinkage of wood, which refers to its lengthwise reduction, is minimal—usually around 0.1% to 0.2%. This makes it largely negligible compared to volumetric shrinkage. As such it's not considered in this calculator.
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