Moisture content and shrinkage

Moisture content (MC) on the dry basis is (m_wet − m_dry) / m_dry × 100. A sample of 120 g that weighs 100 g when oven-dry has an MC of 20 %.

Wood shrinks when MC falls below the fibre saturation point, often taken as about 25–30 %. Tangential shrinkage (along the growth rings) is larger than radial shrinkage (across the rings).

Between 30 % MC and a target MC, a straight-line estimate is change % = S × (30 − target) / 30, where S is the total green-to-oven-dry shrinkage.