Board Foot Calculator — lumber volume

How it works

Lumber is priced by the board foot — a volume equal to 144 cubic inches, or a board 1 inch thick, 12 inches wide and 1 foot long. It measures the amount of wood regardless of the board's exact shape, so a 1×12 and a 2×6 of the same length contain the same board footage.

The handy formula keeps thickness and width in inches and length in feet:

board feet = (thickness × width × length) ÷ 12 × number of boards

Dividing by 12 works because the length is in feet (12 inches) while thickness and width are in inches, so the product is in board feet directly. Multiply by the number of identical boards for the total.

Use nominal dimensions (the "2×4" size a board is sold as) for pricing, since lumber is bought and sold on nominal board footage even though the dressed board is slightly smaller.

Worked example

A single 2 × 6 board 8 feet long is (2 × 6 × 8) ÷ 12 = 96 ÷ 12 = 8 board feet. The definition itself — a 1 in × 12 in × 1 ft board — is (1 × 12 × 1) ÷ 12 = exactly 1 board foot. A 2 × 4 at 8 ft is (2 × 4 × 8) ÷ 12 = 5.33 board feet, and ten 2 × 6 boards at 8 ft are 8 × 10 = 80 board feet.

Frequently asked questions

What is a board foot?

A board foot is a unit of lumber volume equal to 144 cubic inches — the amount of wood in a board 1 inch thick, 12 inches wide and 1 foot long. Lumber is priced per board foot, especially hardwoods and rough-sawn stock.

How do I calculate board feet?

Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12: board feet = (T × W × L) ÷ 12. Multiply by the number of boards for a total. The ÷12 accounts for the length being in feet while T and W are in inches.

Should I use nominal or actual dimensions?

Use the **nominal** size — the "2×4" or "1×6" a board is sold as — because lumber is priced on nominal board footage. The actual dressed dimensions are a bit smaller (a 2×4 is really 1.5 × 3.5 inches), but pricing uses nominal.

How is a board foot different from a linear foot?

A linear foot measures only length, ignoring thickness and width; a board foot measures volume. Two boards of the same length have the same linear footage but different board footage if their cross-sections differ. Lumber priced per board foot accounts for the size of the board.

How does board foot relate to cubic feet?

One cubic foot is 1728 cubic inches and a board foot is 144 cubic inches, so 1 cubic foot = 12 board feet. Board feet are just a lumber-friendly way of measuring the same volume in convenient board-sized units.

How do I estimate the cost of lumber?

Multiply the total board feet by the price per board foot. Calculate the board footage here, then multiply by your supplier's per-board-foot price; add a little for waste and defects, especially with rough lumber.