Board Foot Definition
One Board Foot of wood equals a board that is 12″ x 12″ x 1″, or any other board dimensions that result in the same cubic inch capacity of 144 cubic inches (12″ x 12″ x 1″).
1 Board Foot = 12″ x 12″ x 1″ = 144 cubic inches
Board Feet Calculation Example
What’s the board feet total for a 1×6 that’s 8 ft (96″) in length.
Total Board Feet = (1″ x 6″ x 96″) / 144
= 576 / 144
= 4 Board Feet
- The nominal dimensions (Rough dimensions) are the dimensions of the lumber when it is first cut from a log. Both softwoods & hardwoods use the nominal values for calculating board feet.
Table 1, shows calculated board feet values, for common board sizes.
- When you buy a 2 x 4 softwood board from a store, it’s actual dimensions will be 1-1/2″ x 3-1/2″. However, for calculating the number of board feet, you use the nominal dimensions for the board. In this case, you would use 2″ x 4″, for calculating the board feet.
Table 2, lists nominal & actual board dimensions for softwoods used for framing lumber.
Softwoods start out at the lumber mill dimensioned with nominal dimensions. Before the lumber leaves the mill, it’s trimmed down to a finished size. It’s actual size, dimension wise.
When I say softwoods, I am thinking of woods basically used for the framing of houses. Softwoods commonly used for framing are pine & douglas fir.
Now for hardwoods, the dimensions of the lumber sold are not as standardized, as for softwoods. Suppliers offer hardwood lumber in a range of standard thicknesses, but the width and length are not standardized.
In North America, what’s called the quarter system is used for hardwoods. This system states the nominal (rough) thickness, in 1/4″ increments.
For example, a board with a nominal (rough) thickness of 1″ would be described as a board with a 4/4 thickness.
Table 3, lists the quarter system increments in the 1″ to 2″ range.
Common hardwoods used for furniture building are cherry, walnut, maple, and oak.
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