Wood Moisture Content Calculator
Wood moisture content drives almost every wood-movement and finishing problem, so measuring it accurately matters. The reference standard is the oven-dry method: weigh a sample wet, dry it to constant weight, and express the water lost as a percentage of the oven-dry weight. This calculator applies that formula to your two weights and returns the moisture content percentage. Because MC is referenced to the dry weight, very green wood can read above 100 percent, which is expected.
Moisture content formula
water weight = wet weight - oven-dry weight
MC percent = water weight / oven-dry weight * 100
This is the standard oven-dry moisture content equation. The water lost on drying is divided by the oven-dry weight, not the wet weight, which is the convention used in wood science.
Worked example
A sample weighs 120 g wet and 100 g after oven drying. Water weight = 120 - 100 = 20 g. MC = 20 / 100 * 100 = 20.00 percent. That is on the high side for furniture stock, which is usually dried to 6 to 8 percent, so this board needs more drying time.
Wood moisture content: frequently asked questions
How is wood moisture content defined?
Moisture content (MC) is the weight of water in wood expressed as a percentage of the oven-dry wood weight. The standard oven-dry formula is MC percent equals (wet weight minus oven-dry weight) divided by oven-dry weight, times 100. Because it is based on the dry weight, MC can exceed 100 percent in very green or waterlogged wood.
How do I get the oven-dry weight?
Weigh the sample, then dry it in an oven at about 103 degrees Celsius until its weight stops changing, and weigh again. That final constant weight is the oven-dry weight. The oven-dry method is the reference standard against which moisture meters are calibrated.
What moisture content should furniture wood have?
Wood for interior furniture is usually dried to roughly 6 to 8 percent MC to match heated indoor conditions, while construction lumber is often around 12 to 19 percent. The right target depends on your climate and end use. The USDA Forest Products Laboratory Wood Handbook gives equilibrium moisture content guidance.
Why can moisture content be over 100 percent?
Because MC is the water weight as a fraction of the dry wood weight, not of the total. Green wood can hold more water than the weight of the dry wood fibre itself, giving MC values above 100 percent. This is normal and expected with the oven-dry definition.
Official sources
- USDA Forest Service Forest Products Laboratory: Wood Handbook and wood moisture research. The oven-dry moisture content method is the wood science standard.
- USDA Forest Service Forest Products Laboratory: Wood moisture research.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.