Wood Equilibrium Moisture Calculator

Wood is a hygroscopic material, meaning it can absorb and release moisture from its environment. The equilibrium moisture content (EMC) of wood refers to the moisture content it reaches when it reaches a balance with the surrounding temperature and relative humidity. Understanding the EMC of wood is crucial in applications where dimensional stability and moisture-related issues are important, such as woodworking, construction, and furniture making. This tutorial will guide you through the principles and formulas used to calculate the EMC of wood based on temperature and relative humidity, demonstrating the relevance of physics in this context.

Wood Equilibrium Moisture Calculator
Wood Equilibrium Moisture Calculator Results
EMC = %

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Example Formula

The formula used to calculate the equilibrium moisture content (EMC) of wood is based on the relationship between relative humidity (RH) and temperature (T):

EMC = C × [(RH/100) − (b × T)]


  1. EMC is the equilibrium moisture content of wood (in percentage).
  2. C is the EMC coefficient for a specific wood species and is determined experimentally.
  3. RH is the relative humidity of the environment (in percentage).
  4. b is the temperature coefficient for a specific wood species and is determined experimentally.
  5. T is the temperature of the environment (in °C or °F).

Who wrote/refined the formula

The understanding of wood's moisture behavior and the development of equations for calculating EMC are contributions from various researchers in the field of wood science and engineering. Notable scientists and engineers have refined these formulas over the years, continually improving our understanding of wood's moisture-related properties.

Real Life Application

The knowledge of EMC is critical in various real-life applications involving wood. For example, in woodworking, knowing the EMC helps woodworkers make precise cuts and joints that will not be affected by dimensional changes due to moisture. In construction, understanding the EMC of wood is essential for ensuring the long-term stability and performance of wooden structures.

Key individuals in the discipline

The field of wood science and engineering has seen contributions from notable individuals such as Howard Prestemon, who has extensively researched the relationship between wood moisture and physical properties. Additionally, researchers like Forest Products Laboratory in the United States and organizations like the International Union of Forest Research Organizations (IUFRO) have made significant contributions to understanding wood moisture behavior.

Interesting Facts

  1. The EMC of wood is influenced by various factors, including temperature, relative humidity, wood species, and wood density.
  2. Wood undergoes dimensional changes as it absorbs or releases moisture, which can lead to warping, cracking, and other issues if not properly accounted for.
  3. Wood moisture content is also a critical parameter in determining the energy content and combustion properties of wood as a biofuel.


The equilibrium moisture content (EMC) of wood plays a significant role in its dimensional stability and overall performance. By understanding and calculating the EMC based on temperature and relative humidity, woodworkers, engineers, and researchers can make informed decisions about wood selection, processing, and utilization. Physics, particularly the principles of moisture transfer and equilibrium, provides a fundamental basis for understanding and predicting wood's behavior in relation to moisture content.

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