What is a board foot?

A board foot is a volume of lumber: 144 cubic inches, or a piece 12 inches by 12 inches by 1 inch thick. It is how rough hardwood is priced. A board 1 inch thick, 6 inches wide and 8 feet long is (1 × 6 × 8) ÷ 12 = 4 board feet, whatever its actual finished size.

How do I calculate board feet?

Multiply thickness in inches by width in inches by length in feet, then divide by 12. Or use inches throughout and divide by 144. Multiply by the number of identical boards. This tool does it either way you enter, and adds a waste factor for defects and cutting.

Do I use nominal or actual size?

Rough lumber is usually priced on its rough sawn size, which is close to nominal — a rough 1-inch board really is about an inch. Surfaced (S4S) lumber is smaller than its nominal call-out, but is still often sold by the nominal board foot. Ask the yard which they charge on, and enter that size.

How is board foot different from a linear foot?

A linear foot is just length; a board foot accounts for thickness and width as well, so it measures the amount of wood. Two boards the same length can be very different board footage if one is wider or thicker. Trim and moulding sell by the linear foot; rough boards sell by the board foot.

Board foot calculator

This is arithmetic on the sizes you enter. Yards differ on whether they charge by nominal or actual size and how they round, so use this as an estimate and confirm the tally at the till.

Enter the thickness, width and length of a board and how many you have. The tool works out the board footage — the standard measure of lumber volume — adds a waste factor, and shows the equivalent cubic volume alongside it. Switched to metric, the big figure is cubic metres and the board feet ride underneath, because North American yards still price lumber by the board foot.

Ejemplo resuelto

A board 1 inch thick, 6 inches wide and 8 feet long is (1 × 6 × 8) ÷ 12 = 4 board feet. Ten of them is 40 board feet; add 10% for defects and cutting and you would buy around 44 board feet of rough stock to be safe.

In metric: a board 25 mm thick, 150 mm wide and 2.4 m long is 0.025 × 0.15 × 2.4 = 0.009 m³ (3.8 board feet). Ten of them is 0.09 m³; with 10% on top, 0.099 m³ — about 42 board feet on a North American invoice.

En la obra

Hardwood for a tabletop. The top is 36 × 72 in, glued up from 8/4 stock. Finished it is 36 × 72 × 2 ÷ 144 = 36 board feet — but you buy rough, and rough boards lose width to jointing, length to checked ends and a board or two to grain that will not match. Hardwood waste runs 25–40%, not 10%: 36 × 1.3 = 47 board feet. Set the waste field to what your supplier's boards look like, not what the pine yard's do.

The quarter system. Hardwood thickness is quoted in quarters of an inch: 4/4 is 1 in, 5/4 is 1¼, 6/4 is 1½, 8/4 is 2. And it is billed on the rough thickness — a 4/4 board surfaced to 13/16 still counts as 1 in in the tally. Type the rough figure so the tool and the invoice agree.

Timbers by the board foot. Dimension lumber is sold by the piece, but big timbers and a hardwood order are priced per board foot or per thousand (MBF). Eight 6 × 6 × 10 ft posts are 8 × (6 × 6 × 10 ÷ 12) = 8 × 30 = 240 bf. At a price per MBF, that is 0.24 × the thousand-foot price.

What went wrong?

Quick referencefor lumber

A board foot: 144 in³ — 1 in × 12 in × 12 in
Pies tabla: thickness (in) × width (in) × length (ft) ÷ 12
Per piece: 2×4×8 = 5.3 · 2×6×8 = 8 · 2×8×10 = 13.3 · 2×10×12 = 20 · 2×12×16 = 32 · 4×4×8 = 10.7 · 6×6×10 = 30
Quarters: 4/4 = 1 in · 5/4 = 1¼ · 6/4 = 1½ · 8/4 = 2 · 12/4 = 3
MBF: 1,000 board feet — a price per MBF ÷ 1,000 is the price per bf
Métrico: 1 m³ ≈ 424 board feet · 1 bf = 0.00236 m³ · m³ = thickness (mm) × width (mm) × length (m) ÷ 1,000,000

Waste & overagewhat to add, and why

Hardwood buyers plan 15–25% over the finished board footage: rough lumber has checks, wane and bow, and jointing and planing to size take a quarter inch off each face. The waste field starts at 10% — lift it for rough stock.
Mills sell random widths and lengths, so the tally you pay for is never exactly the tally you drew; buy the next clear board up rather than a piece that just makes it.
For a cut list with many short parts, add for the kerf and the snipe at the ends — a 12 ft board rarely yields twelve 1 ft pieces.

Mistakes to catchbefore you order

Typing the finished (S4S) thickness when the yard bills by rough thickness — 4/4 stock is charged as 1 in even though it planes to ¾.
Entering the length in inches into a field that wants feet; the board-foot formula divides by 12 once, so an inch length inflates the answer twelve times.
Forgetting the piece count: one board at 8 board feet is right, ten of them are 80, and the Number of boards field is easy to leave at 1.

What an inspector looks forthe lumber grader at the mill, and the inspector where the timber is structural

On this part of the job

The grade stamp on the piece: species or species group, grade, moisture condition at surfacing, and the mill. Structural timber must carry one, and an unstamped stick will be refused.
Whether you bought nominal or actual dimensions. Board feet are figured on the rough nominal size, which is why an order can measure short across the tape and still be right.
Moisture. Timber that arrives green and is closed into a wall shrinks; on a finished job that is a callback and on an inspection it can be a deficiency.
For a structural member, that the species and grade on the stamp match what the span table or the engineer assumed.

Have this ready

The tally sheet with each piece's nominal size, length and count.
One piece with the stamp readable, kept where you can point at it.

Every figure an inspector measures against comes from the code your jurisdiction has adopted, the stamped drawing, or the manufacturer's printed instructions — so none of them are printed here. Look the number up in your own book, type it into the tool, and the arithmetic is yours.

La fórmula

board feet = (thickness_in × width_in × length_ft) ÷ 12 · m³ = (thickness_mm × width_mm × length_m) ÷ 1,000,000

A board foot is 144 cubic inches. Thickness and width are in inches and length in feet, so dividing by 12 (rather than 144) accounts for the feet-to-inches on the length. In metric there is no board foot, so the tool converts your sizes to inches and feet to keep the yard's unit while also giving you cubic metres. The cubic metres lead in metric — a 38 × 140 mm board 3.6 m long is 0.0192 m³, or 8.1 board feet.

Preguntas

What is a board foot?: A board foot is a volume of lumber: 144 cubic inches, or a piece 12 inches by 12 inches by 1 inch thick. It is how rough hardwood is priced. A board 1 inch thick, 6 inches wide and 8 feet long is (1 × 6 × 8) ÷ 12 = 4 board feet, whatever its actual finished size.
How do I calculate board feet?: Multiply thickness in inches by width in inches by length in feet, then divide by 12. Or use inches throughout and divide by 144. Multiply by the number of identical boards. This tool does it either way you enter, and adds a waste factor for defects and cutting.
Do I use nominal or actual size?: Rough lumber is usually priced on its rough sawn size, which is close to nominal — a rough 1-inch board really is about an inch. Surfaced (S4S) lumber is smaller than its nominal call-out, but is still often sold by the nominal board foot. Ask the yard which they charge on, and enter that size.
How is board foot different from a linear foot?: A linear foot is just length; a board foot accounts for thickness and width as well, so it measures the amount of wood. Two boards the same length can be very different board footage if one is wider or thicker. Trim and moulding sell by the linear foot; rough boards sell by the board foot.

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