Equilibrium Moisture Content

To use this table

The top row is temperature in fahrenheit. Find your temperature and scan down the column. There are two numbers in each box separated by a "/". The number on the left within each box is the relative humidity and the number on the right is the EMC. Find your relative humidity and you will have the EMC.

The column to the left is wet bulb depression. Scroll all the way down for a brief explanation of what this number means

Remember that Equilibrium Moisture Content and Moisture Content are two different values. A wood stored at a specific temperature and relative humidity will eventually reach that EMC.

  30 35 40 45 50 55 60 65 70 75 80 85 90 95
1 89 90 92 93 93 94 94 95 95 95 96 96 96 96
2 78/15.9 81/16.8 83/17.6 85/18.3 86/19.0 88/19.5 89/19.9 90/20.3 90/20.6 91/20.9 91/21.0 92/21.2 92/21.3 92/21.3
3 67/12.9 72/13.9 75/14.8 78/15.6 80/16.3 82/16.9 83/17.4 84/17.8 86/18.2 86/18.5 87/18.7 88/18.8 89/18.9 89/19.0
4 57/10.8 63/11.9 68/12.9 72/13.7 74/14.4 76/15.1 78/15.6 80/16.1 81/16.5 82/16.8 83/17.0 84/17.2 85/17.3 85/17.4
5 46/9.0 54/10.3 69/11.2 64/12.0 68/12.7 70/13.4 73/13.9 75/14.4 77/14.9 78/15.2 79/15.5 80/15.7 81/15.9 82/16.1
6 36/7.4 45/8.8 52/9.9 58/10.7 62/11.5 65/12.2 68/12.7 70/13.3 72/13.7 74/14.0 75/14.3 76.14.5 78/14.7 79/14.9
7 27/5.7 37/7.4 45/8.6 51/9.5 56/10.3 60/11.0 63/11.6 66/12.1 68/12.5 70/12.9 72/13.2 73/13.5 74/13.7 75/13.9
8 17/3.9 28/6.0 37/7.4 44/8.5 50/9.4 54/10.1 58/10.7 61/11.2 64/11.6 66/12.0 68/12.3 70/12.5 71/12.8 72/12.9
9 6/1.6 19/4.5 29/6.2 37/7.5 44/8.5 49/9.3 53/9.9 56/10.4 59/10.9 62/11.2 64/11.5 66/11.8 68/12.0 69/12.2
10 --- 11/2.9 22/5.0 31/6.5 38/7.6 44/8.4 48/9.1 52/9.7 55/10.1 58/10.5 61/10.9 63/11.2 65/11.4 66/11.6
11 --- 3/0.8 15/3.5 25/5.3 32/6.7 39/7.6 43/8.3 48/8.9 51/9.4 54/9.8 57/10.1 59/10.5 61/10.7 63/11.0
12 --- --- 8/1.9 19/4.2 27/5.7 34/6.8 39/7.6 44/8.3 48/8.8 51/9.3 54/9.7 56.10.0 58/10.2 60/10.5
13 --- --- --- 12/2.9 21/4.8 28/6.0 34/6.9 39/7.7 44/8.3 47/8.7 50/9.1 53/9.5 55/9.7 57/10.0
14 --- --- --- 6/1.5 16/3.9 24/5.3 30/6.3 36/7.1 40/7.7 44/8.2 47/8.6 50/9.0 52/9.3 55/9.5
15 --- --- --- --- 10/2.8 19/4.5 26/5.6 32/6.5 36/7.2 41/7.7 44/8.1 47/8.5 49/8.8 52/9.1
16 --- --- --- --- 5/1.5 14/3.6 21/4.9 27/5.8 33/6.6 37/7.2 41/7.7 44/8.1 47/8.4 49/8.7
17 --- --- --- --- --- 9/2.5 17/4.1 24/5.2 29/6.0 34/6.7 38/7.2 41/7.6 44/8.0 46/8.2
18 --- --- --- --- --- 5/1.3 13/3.2 20/4.5 25/5.5 31/6.2 35/6.8 38/7.2 41/7.6 44/7.9
19 --- --- --- --- --- --- 9/2.3 16/3.8 22/4.9 28/5.6 32/6.3 36/6.7 39/7.2 42/7.5
20 --- --- --- --- --- --- 5/1.3 13/3.0 19/4.3 24/5.1 29/5.8 33/6.3 36/6.8 39/7.1
21 --- --- --- --- --- --- 1/0.2 8/2.3 15/3.7 21/4.7 26/5.4 30/6.0 34/6.5 37/6.8
22 --- --- --- --- --- --- --- 6/1.4 12/2.9 18/4.1 23/5.0 28/5.6 31/6.1 34/6.4
23 --- --- --- --- --- --- --- 2/0.4 9/2.3 15/3.5 20/4.5 25/5.2 29/5.7 32/6.1
24 --- --- --- --- --- --- --- --- 6/1.5 12/2.9 18/4.0 23/4.8 26/5.3 30/5.7
25 --- --- --- --- --- --- --- --- 3/0.7 10/2.3 15/3.5 20/4.3 24/4.9 28/5.3
26 --- --- --- --- --- --- --- --- --- 7/1.7 12/3.0 18/3.9 22/4.6 26/5.1
27 --- --- --- --- --- --- --- --- --- 4/0.9 10/2.4 15/3.4 19/4.2 23/4.8
28 --- --- --- --- --- --- --- --- --- 1/0.2 7/1.8 13/3.0 17/3.8 22/4.4
29 --- --- --- --- --- --- --- --- --- --- 5/1.1 11/2.4 15/3.3 20/4.0
30 --- --- --- --- --- --- --- --- --- --- 3/0.3 9/1.7 13/2.8 17/3.6
32 --- --- --- --- --- --- --- --- --- --- --- 4/0.9 9/2.1 14/3.0
34 --- --- --- --- --- --- --- --- --- --- --- --- 5/1.3 10/2.3
36 --- --- --- --- --- --- --- --- --- --- --- --- 1/0.4 6/1.5
38 --- --- --- --- --- --- --- --- --- --- --- --- --- 2/0.6

This information was collected from "Dry Kiln Operator's Manual"

Wet Bulb Depression

As water evaporates it cools a surface. Water evaporates more slowly as the air becomes saturated so the cooling lessens. Many kiln operators use a wet bulb/ dry bulb system to determine relative humidity. This system has two thermometers, called bulbs. One is simply exposed the air inside the kiln chamber and this one is called the dry bulb. The wet bulb is a thermometer with a wick around the bulb that's kept constantly wet so it measures the cooling effect of the evaporation. The difference between the readings of the wet and dry bulbs is called the "wet bulb depression" and this is generally a more accurate way of determining relative humidity than hygrometers.