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.
- Skill level:
- Moderately Easy
Things you need
- Tape measure
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.
Tips and warnings
- A board foot can be any shape, but derives its name from a square board measuring 12 by 12 inches and 1-inch thick.
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- "Webster's New World College Dictionary 4th Edition"; Michael Agnes, ed.; 2007
- Dave's Shop Talk; Inches to Decimal Foot; David E. Osborne
- The World of Math Online: Volume Formulas
- North Dakota State University Dickinson Research Extension Center; Weight of Water per Acre from One Inch of Rain; Llewellyn L. Manske PhD
- Ohio State University; Determining Diameter, Merchantable Height, and Volume; Randall B. Heiligmann and Stephen M. Bratkovich