Board foot calculator

A board foot is 144 cubic inches of timber — thickness × width × length in inches, divided by 144. It is a measure of volume, not of area or of length.

The trap is nominal versus actual dimensions. Timber sold as a two-by-four is not two inches by four; it is milled down to about 1.5 by 3.5 after drying and planing. Board footage is conventionally billed on the nominal size, which is why a yard quotes you for more wood than you physically receive — that is the convention, not a swindle, but it means measuring your actual boards and calculating from those gives a different answer than the invoice. Rough-sawn timber is the exception: it is close to its nominal size, which is part of why it is cheaper per board foot.