Computing Moisture Content of Wood, Woodbin, Woodworking Software. http://www.woodbin.com
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 an equilibrium with its environment and is no longer gaining or losing moisture. Here is a calculator for computing the EMC of wood at or below the fiber saturation point (about 30% moisture content) given the temperature and relative humidity.