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Wood Equilibrium Moisture Content Table And Calculator

This calculator and converter requires the use of Javascript enabled and capable browsers. It is designed to give the equilibrium moisture content of non-living wood, natural or cut, based on the data entered, at or below the fiber saturation point (about 30% moisture content) given the temperature and relative humidity. The moisture content of wood is directly related to the humidity and temperature of the surrounding air. The equilibrium moisture content (EMC) occurs when the wood has reached a water content equilibrium with its environment and is no longer gaining or losing moisture. The calculator defaults are applicable for our desert environment. The math behind the EMC Equation is as follows. The table below was derived from this formula also. Enter the values and click on Calculate for the EMC to be returned.

M = 1800/W [ KH/(1-KH) + (K1KH + 2K1K2K2H2) / (1 + K1KH + K1K2K2H2)]

Where:

M = moisture content (%)
T = temperature (oF)
H = relative humidity (%) / 100
W = 330 + 0.452T + 0.00415T2
K = 0.791 + 0.000463T - 0.000000844T2
K1 = 6.34 + 0.000775T - 0.0000935T2
K2 = 1.09 + 0.0284T - 0.0000904T2

We obtained the basic information to create the calculator and table from the U.S. Forest Products Laboratory. The table below provides EMC values for an equitable representative range of atmospheric conditions that wood is likely to be a participant within. Values in this table are applicable to wood of any species for most practical purposes. This is a link to the United States Department of Agriculture Forest Service report that contains the formula found on this page. http://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf

EMC Calculator
Required Data Entry
Temperature (F) Degrees
Relative. Humidity Percent
EMC Percent
  
EMC Table
Relative
Humidity
(%)
Ambient Air Temperature - Degrees Fahrenheit
0 30 40 50 60 70 80 90 100 110 120 130
5 1.4 1.4 1.4 1.3 1.3 1.3 1.2 1.2 1.1 1.1 1.0
10 2.6 2.6 2.6 2.5 2.5 2.4 2.3 2.3 2.2 2.1 2.0
15 3.7 3.7 3.6 3.6 3.5 3.5 3.4 3.3 3.2 3.0 2.9
20 4.6 4.6 4.6 4.6 4.5 4.4 4.3 4.2 3.0 3.9 3.7
25 5.5 5.5 5.5 5.4 5.4 5.3 5.1 5.0 4.9 4.7 4.5
30 6.3 6.3 6.3 6.2 6.2 6.1 5.9 5.8 5.6 5.4 5.2
35 7.1 7.1 7.1 7.0 6.9 6.8 6.7 6.5 6.3 6.1 5.9
40 7.9 7.9 7.9 7.8 7.7 7.6 7.4 7.2 7.0 6.8 6.6
45 8.7 8.7 8.7 8.6 8.5 8.3 8.1 7.9 7.7 7.5 7.2
50 9.5 9.5 9.5 9.4 9.2 9.1 8.9 8.7 8.4 8.2 7.9
55 10.4 10.4 10.3 10.2 10.1 9.9 9.7 9.5 9.2 8.9 8.7
60 11.3 11.3 11.2 11.1 11.0 10.8 10.5 10.3 10.0 9.7 9.4
65 12.4 12.3 12.3 12.1 12.0 11.7 11.5 11.2 11.0 10.6 10.3
70 13.5 13.5 13.4 13.3 13.1 12.9 12.6 12.3 12.0 11.7 11.3
75 14.9 14.9 14.8 14.6 14.4 14.2 13.9 13.6 13.2 12.9 12.5
80 16.5 16.5 16.4 16.2 16.0 15.7 15.4 15.1 14.7 14.4 14.0
85 18.5 18.5 18.4 18.2 17.9 17.7 17.3 17.0 16.6 16.2 15.8
90 21.0 21.0 20.9 20.7 20.5 20.2 19.8 19.5 19.1 18.6 18.2
95 24.3 24.3 24.3 24.1 23.9 23.6 23.3 22.9 22.4 22.0 21.5
98 26.9 26.9 26.9 26.8 26.6 26.3 26.0 25.6 25.2 24.7 24.2
Updayed 8.15.11
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