A cord is a traditional unit of volume used to measure stacked firewood. In the United States, the cord is defined legally as the volume of a stack of firewood 4 feet (1.2 meter) wide, 8 feet (2.4 meter) long, and 4 feet (1.2 meter) high. (In Maryland, the law specifies that the wood be stacked “tight enough that a chipmunk cannot run through it.”) The name comes from an old method of measuring a stack of firewood using a cord or string.
In the U.S. timber industry, the cord is also used as a unit of weight for pulpwood. The weight varies with tree species, ranging from about 5,200 pounds (2,358 kilograms) for pine to about 5,800 pounds for hardwood.