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How to Calculate the Board-Foot Volume of Timber

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.

Things You'll Need

  • Tape measure
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Instructions

    • 1

      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.

    • 2

      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.

    • 3

      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.

    • 4

      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.