How do you calculate board feet?

Thickness (in) × width (in) × length (ft) ÷ 12. Or thickness × width × length all in inches ÷ 144. A 1 × 6 × 8 ft board is 4 board feet.

Is a 2×4 measured at 2 × 4?

For board-foot pricing, yes, nominal sizes are used: a 2×4×8 is 5.33 board feet even though it is 1½ × 3½ actual. Softwood framing is usually priced per piece anyway.

Quarters of an inch of rough thickness: 4/4 is 1 in, 5/4 is 1¼, 6/4 is 1½, 8/4 is 2 in. Surfacing removes about a quarter inch.

Board foot calculator

Form 100 · Materials estimateFigures checked 2026-09-04

US customary

Measurements

Thickness(in)4/4 = 1 in, 5/4 = 1.25, 6/4 = 1.5, 8/4 = 2

Width(in)

Length(ft)

Pieces

What you need

Quantity · Amount

01Board feet, each piece1 × 6 in × 8 ft ÷ 124 bd ft
02Board feet, all pieces$7 per board foot4 bd ft$28

Total, lumber$28

Rough lumber is measured at its nominal thickness; surfaced 4/4 stock (¾ in) still counts as 1 in.

Prices — put in what you were quoted

Price($ per board foot)Red oak $4–7, walnut $10–15, poplar $3–5 per board foot

Total, lumber4 board feet$28

Where these figures come from

Board foot = 144 cubic inches by definition; nominal (rough) dimensions are used in the trade.

Hardwood is sold by the board foot: a piece 1 inch thick, 12 inches wide and 12 inches long. Type the nominal thickness in quarters or inches (4/4 = 1 in, 8/4 = 2 in), the width, the length and how many pieces, and the sheet gives board feet and cost at the price per board foot you enter.

Worked examples

Ten 4/4 boards, 6 in × 8 ft: 40 bd ft — board feet, all pieces, about $280 in lumber.
One 8/4 slab, 12 in × 10 ft: 20 bd ft — board feet, all pieces, about $140 in lumber.

How it is worked out

Board feet = thickness (in) × width (in) × length (ft) ÷ 12, × the number of pieces. Cost = board feet × price per board foot.

The figures behind it

Board foot = 144 cubic inches by definition; nominal (rough) dimensions are used in the trade.

Every figure here is an estimate. Materials vary with moisture, compaction and product; order a little extra and confirm quantities with your supplier.

Questions people ask

How do you calculate board feet?: Thickness (in) × width (in) × length (ft) ÷ 12. Or thickness × width × length all in inches ÷ 144. A 1 × 6 × 8 ft board is 4 board feet.
Is a 2×4 measured at 2 × 4?: For board-foot pricing, yes, nominal sizes are used: a 2×4×8 is 5.33 board feet even though it is 1½ × 3½ actual. Softwood framing is usually priced per piece anyway.
What does 4/4 mean?: Quarters of an inch of rough thickness: 4/4 is 1 in, 5/4 is 1¼, 6/4 is 1½, 8/4 is 2 in. Surfacing removes about a quarter inch.

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