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1-5. BF Compution

A BF is a unit measure representing an area of 1 foot by 1 foot, 1 inch thick. The number of board feet in a piece of lumber can be computed using one of the following methods:

a. Rapid Estimate. You can estimate BF rapidly by using Table 1-5. For example, reading the table, you can see that if a 2-inch by 12-inch board is 16 feet long, your board feet would be 32.

Table 1-5. Board feet

b. Arithmetic Method. To determine the number of BF in one or more pieces of lumber use the following formula:

NOTE: If the unit of measure for length is in inches, divide by 144 instead of 12.

SAMPLE PROBLEM 1: Find the number of BF in a piece of lumber 2 inches thick, 10 inches wide, and 6 feet long (Figure 1-21).

SAMPLE PROBLEM 2: Find the number of BF in 10 pieces of lumber 2 inches thick, 10 inches wide, and 6 feet long.

SAMPLE PROBLEM 3: Find the number of BF in a piece of lumber 2 inches thick, 10 inches wide, and 18 inches long.

Figure 1-21. Lumber dimensions

c. Tabular Method. The standard essex board measure table (Figure 1-22) is a quick aid in computing BF. It is located on the back of the blade of the framing square. In using the board measure table, make all computations on the basis of 1-inch thickness. The inch markings along the outer edge of the blade represent the width of a board 1 inch thick. The third dimension (length) is provided in the vertical column of figures under the 12-inch mark.

Figure 1-22. Essex board measure table

SAMPLE PROBLEM: To compute the number of BF in a piece of lumber that is 8 inches wide, 14 feet long, and 4 inches thick-

1. Find the number 14 in the vertical column under the 12-inch mark.

2. Follow the guideline under number 14 laterally across the blade until it reaches the number on that line that is directly under the inch mark matching the width of the lumber.

Example: Under the 8-inch mark on the guideline, moving left from 14, the numbers 9 and 4 appear (9 and 4 should be on the same line as 14). The number to the left of the vertical line represents feet; the number to the right represents inches.

3. The total number is 37 1/3 BF. BF will never appear in a decimal form.

Example solution: 1" x 4" x 8' x 14'	Feet	Inches
	9	4
	4	4
	36	16/12
		1 4/12
		36+ 1 1/3	= 37 1/3 BF

NOTE: 1" x 4" = Always multiply the number of pieces by the thickness and multiply the feet and inches by the sum of pieces and thickness.

Curriculum design: David L. Heiserman
Publisher: SweetHaven Publishing Services