Hardwood dealers sell by the board foot, so knowing the formula is the difference between an accurate quote and a surprise at the register. This calculator takes thickness (including 4/4 through 16/4 quarter sizes), width, length, and piece count, then returns board feet per piece, the total, and the cost at your price per board foot — plus the equivalent price per linear foot for comparing yards.
Framing a wall instead? The stud wall calculator counts studs, plates, and headers, and the deck calculator turns deck size into boards and joists. For metric conversions of any dimension, use the unit converter.
Frequently asked questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A board foot is 144 cubic inches — the volume of a board 1 inch thick, 12 inches wide, and 1 foot long. So a 2×6 that is 10 feet long is 2 × 6 × 10 ÷ 12 = 10 board feet. If you measure length in inches instead, divide by 144. For a stack of identical boards, work out one piece and multiply by the count. The calculator does all of this at once and accepts lengths like 8' 6" or 2.4m.
Do I use nominal or actual size for board feet?
By trade convention, softwood dimension lumber is tallied on nominal size, so a 2×4 counts as 2 × 4 even though it measures 1½" × 3½" after drying and planing. Rough hardwood is sold by its rough thickness in quarters (4/4, 8/4) and its measured width, before surfacing. If you are pricing a board that has already been surfaced, ask the yard whether their per-board-foot price is based on rough or finished size — most price on rough, so the surfaced board costs more per actual cubic inch.
What do 4/4, 5/4, and 8/4 mean?
Hardwood thickness is quoted in quarter inches. 4/4 ("four quarter") is 1 inch rough, 5/4 is 1¼ inch, 6/4 is 1½ inch, 8/4 is 2 inches, and 12/4 is 3 inches. These are rough-sawn sizes: after planing, 4/4 stock typically finishes around ¾" to 13/16". Type a quarter size straight into the thickness box or tap one of the chips, and the calculator converts it to inches for the board-foot formula. If a dealer lists 4/4 lumber "S2S," it has been surfaced on two sides but is still tallied at its 1-inch rough thickness.
How do I convert linear feet to board feet?
Board feet per linear foot equals thickness × width ÷ 12 (nominal inches). A 2×4 is 0.667 BF per foot, a 2×6 is exactly 1, a 2×12 is 2, and a 1×6 is 0.5. Multiply by the linear footage to get board feet, or divide board feet by that figure to go the other way. The converter under the result does this for common nominal sizes, which is handy when a lumberyard quotes one unit and a store quotes the other.
How much extra lumber should I buy?
For furniture and cabinet work in rough hardwood, plan on 20–30% over the finished board footage to cover defects, snipe, knots, and grain you want to avoid. For framing and dimension lumber, 10% is a common allowance. Figures depend heavily on grade: FAS hardwood yields more clear material than Common grades. This calculator reports the exact board footage of what you enter, so add your waste by bumping the piece count or length. Buying a little extra of the same batch also keeps color and grain consistent across a project.