🪵 Board Foot Calculator — Lumber to Square Feet Conversion

A 2×4 that is 8 feet long contains 5.33 board feet using nominal dimensions: 2 × 4 × 8 ÷ 12 = 5.33 bd ft. Board foot math always runs on nominal size — the labeled size, not the milled 1.5 × 3.5 inch reality. At $4.50 per board foot, that stick costs about $24.

A kiln-dried 2×4×8 in pine or fir weighs about 10 lbs. The same stick pressure-treated with water-based preservative weighs 13–14 lbs, and a soaked, un-dried treated stick from the yard can top 20 lbs until it seasons. For quick estimating, figure roughly 1.25 lbs per foot for KD 2×4 pine — so a 10-footer is ~12.5 lbs and a 12-footer ~15 lbs.

About 15 lbs in kiln-dried pine: a 2×6×8 contains 8 board feet, and softwood runs roughly 2 lbs per board foot. Pressure-treated versions weigh 20–24 lbs. Our calculator above applies species density automatically — switch between pine (26 lb/ft³), plywood-core (32 lb/ft³), and oak (47 lb/ft³) to see the spread.

One board foot is a volume of 144 cubic inches — think a plank 12 inches wide, 12 inches long, and 1 inch thick. The abbreviation is bd ft, FBM (foot board measure), or just BF in lumber pricing. It measures volume, not area or length, which is why a 2-inch-thick board yields only half as many square feet per board foot as 1-inch stock.

Multiply thickness in inches × width in inches × length in feet, then divide by 144. A 1×6 that is 10 feet long: 1 × 6 × 10 ÷ 144 = 0.417 bd ft. The two habits that keep the math honest: use nominal (labeled) dimensions, and use length in feet — not inches. For a whole project, list every part with its bd ft and add the column; the Cut list mode above does exactly that.

Divide board feet by thickness in inches. One board foot of 1-inch stock covers exactly 1 square foot; of 2-inch stock, half a square foot. So 200 board feet of 4/4 lumber is 200 square feet of surface, while 200 bd ft of 8/4 is only 100 sq ft. The reverse: multiply square feet by thickness in inches.

A linear foot is 12 inches of length and ignores width and thickness entirely; a board foot is 144 cubic inches of volume and ignores nothing. A 12-foot 1×6 and a 12-foot 2×12 are both 12 linear feet, but the 1×6 is 6 bd ft and the 2×12 is 24 bd ft. Linear feet price trim, molding, and flooring; board feet price dimensional hardwood and rough lumber.

A 4×8 sheet contains 32 square feet of surface, so it equals 32 board feet at 1-inch thickness — but plywood is never sold by the board foot. It is sold by the sheet, by thickness, which is why a 3/4-inch sheet (nominally 24 'board feet of surface') does not cost 24× a 1-inch price. Mixing units only makes sense when a cabinet order combines sheet goods for carcasses with board-foot lumber for face frames.

It depends entirely on species and grade. Construction-grade softwood runs roughly $2–4 per bd ft; common hardwoods like red oak or ash around $5–8; walnut and cherry $8–15; and figured or curly stock can exceed $20 per bd ft. Enter your species and price in the calculator to see per-piece and order totals — the default $4.50 reflects a mid-grade hardwood counter price.

Hardwood thickness is quoted in quarters of an inch, rough-sawn: 4/4 (four quarters) is 1 inch rough, 8/4 is 2 inches, 5/4 is 1¼ inches. Board foot pricing is charged on that rough nominal thickness before surfacing — a 4/4 board planed to 3/4 inch still costs its full 4/4 board footage. That gap between rough and finished thickness is the lumber yard's margin for the surfacing you did not have to do.

Add up the board footage of every part from your cut list, then add 15–30% for waste, defects, and grain matching — straight paint-grade work can live with 15%, but walnut tabletops with matched grain routinely burn 30%. A 60 × 30-inch dining top at 8/4 needs 100 sq ft × 2 = 200 board feet of surface, so order roughly 250–260 bd ft.