Determining the board-foot volume of timber requires measuring the timber, then using basic math to convert volume in inches to volume in board feet.
The board foot, a unit of volume rather than length, is the standard measure for quantities of timber. A board foot does not have to be a foot long; it can be any shape so long as the volume equals 144 cubic inches.
Timber is wood suitable for use in building projects, such as beams and planks.
Measure, in feet and inches, the length, width and the thickness of each piece of timber for which the board-foot volume is to be calculated.
Convert the measurements to decimals by multiplying the inches component by 0.0833, the decimal equivalent of 1 inch.
For example, the decimal equivalent of 1 foot and 2 inches is 1. 1666 - 1 foot + 2 x 0.0833 = 1.1666 feet.
Determine the volume in cubic feet by using the formula volume = length x width x thickness. For example, the volume of a piece of wood 12 feet long, 1.1666 feet wide and 0.5 feet thick is 6.9996 cubic feet.
Convert to cubic inches by multiplying the result from Step 2 by 1,728, the number of cubic inches in one cubic foot.
For example, 6.9996 cubic feet is 12095.3088 cubic inches -- 6.9996 x 1,728 = 12095.3088.
Divide the number of cubic inches in the result from Step 3 by 144, the number of cubic inches in 1 board-foot. The result is the board-foot volume of the timber
For example, 12095.3088 divided by 144 = 83.9952, so the volume of the timber is 83.9952 board-feet.
A board foot can be any shape, but derives its name from a square board measuring 12 by 12 inches and 1-inch thick.