While the lineal (running) foot is great for equal sized boards i.e. 2×4’s or hardwood decking. What happens when the thickness and widths vary from board to board?
In this instance, most specialty lumber yards use the board foot. A board foot is actually 1/12 of a cubic foot of rough lumber, or 144 cubin inches. Visually, it’s equal to a 1″ x 12″ x 12″ piece of lumber. This final measurement can be reached by a combination of many dimensions, which always multiply to 144 or 1 board foot.
To calculate the board footage of any given hardwood multiply it’s thickness by it’s width, then multiply that sum by the length. Devide this final number by 144 and bingo your board footage.
Remember as many rough sawn hardwoods are not perfectly straight factor some waste onto what you truly need. Many contractors order up to 30% in waste to ensure they have enough product for a “smooth ” install.