ENCYCLOPEDIA OF WOOD

CALCULATING BOARD FEET

Ordering lumber by the board foot

Because the board foot is a unit of measurement that offers a standard way of totaling the volume of stock regardless of dimensions, it is commonly used when dealing with lumber. As shown at left, the standard board foot is equivalent to a piece that is 1 inch thick, 12 inches wide and 12 inches long. To calculate the number of board feet in a particu­lar piece of wood, multiply its three dimensions together. Then divide the result by 144 if the dimensions are all in inches, or by 12 if one dimension is expressed in feet. For the standard board, the formula is:

1" x 12" x 12" + 144 = 1 (or 1" x 12" x Г + 12 = 1). So if you had an 8-foot-long l-by-3, you would cal­culate the board feet as follows: 1x3x8h-12 = 2 (or 2 board feet). Other examples are shown in the illustration. Remember that board feet are calculat­ed on the basis of nominal rather than actual sizes.

Making and using a cutting list

A cutting list records the finished sizes of the lumber needed for a particular pro­ject. It may be included with the plans you purchase; otherwise, you will have to fashion your own based on a drawing of the design. Tally up the number of board feet for each piece using the formula shown on page 43; tack on an extra 30 to 40 percent to account for defects in the wood and waste. For the project shown on this page, which totals roughly 16 board feet, you should order at least 20 or 25 board feet of 4Aj lumber in addition to the necessary quantity of plywood sheet­ing. The cutting list should include the name of the part, the quantity, the dimen­sions of the pieces and the kind of wood suitable for the project. For convenience, assign a letter to each piece.