WOOD BEAM SIZINGTM  BASIC

Dimension lumber

Dimension lumber is sawn lumber, nominal 2, 3 or 4-inch thick.

Standard dimension lumber is pre-sawn and pre-cut to size and visually graded: 2-by-4, 2-by-6, 2-by-8, 4-by-4, 4-by-6 and so forth.

Widely available in lengths of 8 to 16 feet, pre-cut to the nearest
2-foot length. Lengths up to 26 feet, in some sizes, also usually available.

Compare with beams - defined by NDS as 5-inches or larger in both width and depth.