What is the actual size of a 2x4?

The actual size of a 2x4 is closer to 1 1/2 by 3 1/2 inches. This is because as wood dries out, it shrinks. Since wood shrinks across the grain, its width is affected much more than its length. For example, a 6-foot-long 2x4 is probably actually 6 feet long.

The real size of a piece of lumber also depends on whether it is a softwood, hardwood or plywood. Softwoods come in standard 1x and 2x sizes, while the sizes of hardwoods are more variable. The size of a piece of hardwood also depends on whether it was surfaced on one or two sides.