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Board Foot Calculator

Hardwood and rough lumber are sold by the board foot, not by the piece. Enter the board dimensions and how many you need, and get the total board feet, and the bill, at your yard's price.

Diagram of a board showing its length in feet and the end face with thickness and width in inches
A board foot is volume: thickness × width (inches) × length (feet), divided by 12.

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How board feet are calculated

A board foot is a volume of wood: a board 12 in wide × 12 in long × 1 in thick makes 144 cubic inches. The formula is board feet = (thickness in inches × width in inches × length in feet) ÷ 12. Multiply by the number of pieces for the total.

Worked through: a 2×6 that is 8 ft long is (2 × 6 × 8) ÷ 12 = 8 board feet. A 1×12 at 6 ft is (1 × 12 × 6) ÷ 12 = 6 board feet. If the yard prices by the piece instead, divide its price by the board feet per piece to compare boards fairly.

Two lumber-yard realities: dimensions are nominal: a "2×6" is actually 1.5 × 5.5 in, and board-foot pricing at hardwood yards is normally calculated on the nominal (or rough) size, not the dressed size. And rough lumber loses thickness when surfaced, so buy 10–20% extra for waste, defects and milling, the waste allowance most woodworkers plan on. Counting studs for a wall frame? The Stud Calculator turns wall length and spacing into a stud count.

Sources

The figures behind this calculator come from published manufacturer data and industry standards:

Worked examples

Ten 2 × 6 boards, 8 ft long

(2 × 6 × 8) ÷ 12 = 8 board feet per board.

80 board feet total

Four 1 × 12 boards, 6 ft long

(1 × 12 × 6) ÷ 12 = 6 board feet per board.

24 board feet total

Five 4 × 4 posts, 12 ft long

(4 × 4 × 12) ÷ 12 = 16 board feet per post.

80 board feet total

Frequently asked questions

How many board feet are in a 2×4×8?
(2 × 4 × 8) ÷ 12 = 5.33 board feet on nominal size. Note that construction 2×4s are usually priced per piece, not per board foot. Board-foot pricing is the hardwood and rough-lumber system.
What is the difference between board feet and linear feet?
Linear feet only measure length. A 10 ft board is 10 linear feet whatever its size. Board feet measure volume, so a 10 ft 2×12 (20 board feet) counts four times a 10 ft 1×6 (5 board feet).
Should I calculate board feet from actual or nominal dimensions?
Hardwood yards typically charge on the nominal/rough dimensions the lumber was sawn to, before surfacing. If you're calculating how much finished wood a project needs, use actual finished sizes for the requirement, then add waste.
How much extra lumber should I buy?
Add 10% for straight, clear stock and up to 20% for rough hardwood that needs milling and defect cut-out. Buying all a project needs in one trip also keeps colour and grain consistent.

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Estimate disclaimer: results are planning estimates based on standard manufacturer yields and coverage figures. Site conditions, product choice and installation method change actual quantities. Verify before you buy, and follow local building code for structural work. This tool does not replace professional engineering advice.

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