Softwood is sold in standard dimensions, hardwoods is generally sold in random widths and lengths. So to tell how much hardwood is in a board, they are measured in board feet. A board Foot is a volume measurement. One board foot equals 144 cubic inches.
Often, a board foot is illustrated as a board 1″-thick x 12″-wide x 12″-long, but rarely will you find lumber in those dimensions. Any board containing a total of 144 cubic inches of wood equals one board foot, regardless of its proportions.
Let’s say you’ve found a board that’s 4/4 – hardwood is measured in 1/4″ (so 4/4″ = 1″) x 8″ x 96″
To find the volume of wood, or the number of board feet, simply use this formula.
(TxWxL)/144 (units all in inches)
So our piece of wood 4/4″ x 8″ x 8′
Board feet = (1x8x96)/144 = 5.3 Bft.