Bf, board foot (or board feet) is the unit of measure for lumber. One board foot is defined as 144" cubic inches of wood (the benchmark of 12"x12"x1" is often given). Lumber is sometimes expressed in explicit thicknesses (0.75"), but more often expressed as a fraction. 4/4, pronounced as Four Quarters, is generally betwen 3/4" and 1" thick. 8/4 (Eight Quarters) is generally between 1-1/2" and 2" thick. When calculating board feet, lumber marked as 4/4 is generally assumed to be 1" thick (regardless of actual thickness), and 8/4 lumber is generally assumed to be 2" thick (again, regardless of actual thickness).
So one board foot of 4/4 lumber adds up to about 144 cubic inches, whether it's 12"x12" (12x12x1=144) or 6"x24" (6x24x1=144) or whatever, it's about 144 cubic inches. And one board foot of 8/4 lumber might about 6"x12" (6x12x2=144). It's half as wide, but twice as thick.
For your bass body wings, you'll probably want 8/4 lumber unless you are putting a very thick top on the thing. You basically need two pieces that are about 6" wide and about 20" long (and since it's 8/4, about 2" thick). That's just a touch under 2 bf per side. According to woodworkers source' online calculator ([Invalid or Expired Link Removed]), two 8/4 pieces of mahogany 6" wide and 20" long is 3.33 board feet.
If you can find a lumberyard that will cut to your specified dimensions, you may save some money by not buying more than you need. If you buy online, you may not have that option. For example, the woodworkers source website shopping cart does not allow fractional quantities, but if you call them, they may be more flexible.
I hope that helps...and I hope I'm not way off. I'm an amateur at this, and that is just what I have learned from online research.
