A board foot is a unit of volume used to tally lumber. A board 12 inches long, 12 inches wide, and 1 inch thick contains one board foot. A board 24 inches long, 6 inches wide, and 1 inch thick contains the same volume.
Choose the formula for your units
This gives board feet for one board. Multiply by quantity only when all boards have matching dimensions. If length is in inches instead of feet, divide by 144. Entering 96 inches into the feet field makes the result twelve times too large.
A mixed order, worked out
Four boards measuring 1 × 6 inches and 8 feet long contain 4 board feet each, or 16 total. Two boards measuring 1½ × 8 inches and 6 feet long contain 6 board feet each, or 12 total. Add the groups to get 28 board feet.
At a sample price of $7 per board foot, the material costs $196 before extra material or charges. If the groups have different prices, price each group separately before adding the costs.
Rough versus finished thickness
The quarter system describes rough thickness: 4/4 means 1 inch, 5/4 means 1¼ inches, 6/4 means 1½ inches, and 8/4 means 2 inches. Surfacing removes material. The dimensions a supplier uses for billing are not necessarily those of the finished piece.
For physical volume, measure the actual material. For a purchasing estimate, ask how the supplier tallies thickness, width, and length. Do not silently combine different conventions.
Allow for the work ahead
A finished cutting list is a net requirement. Milling, end checks, grain matching, knots, and joinery can increase the amount of rough wood required. There is no universal waste percentage: a narrow rail and a wide show panel have different selection requirements.
Use the board foot calculator for each size, then the cost calculator to apply your quote and allowance.