- What's a board foot?
- A board foot is a unit of lumber volume equal to a piece 1 inch thick by 12 inches wide by 12 inches long — 144 cubic inches. Hardwood lumber in the US and Canada is almost always priced by the board foot. Softwood dimensional lumber (2x4s at the home center) is usually priced by the piece or linear foot, but board feet still apply if you want to compare.
- What's the formula?
- Board feet = (thickness × width × length) ÷ 144, with all dimensions in inches. For multiple identical pieces, multiply by the piece count. Example: a 1 in × 6 in × 96 in board = (1 × 6 × 96) ÷ 144 = 4 board feet.
- Nominal vs actual — which dimension do I use?
- Depends on what your supplier prices on. Most hardwood dealers price on rough (full nominal) dimensions even though the boards they hand you are surfaced (smaller). A 4/4 board priced at 'one inch thick' is really about 13/16 in surfaced. Read the price sheet — if it says '4/4 cherry $7/bdft,' use 1 in for thickness in this calculator.
- What does 4/4, 5/4, 8/4 mean?
- Quarter notation, common at hardwood yards. 4/4 = four-quarters of an inch = 1 in rough. 5/4 = 1.25 in. 6/4 = 1.5 in. 8/4 = 2 in. The denominator is always 4. Boards are sold rough at these thicknesses; surfaced (S2S or S4S) boards are typically 1/8 to 3/16 in thinner after planing.
- Why not just use cubic feet?
- Tradition, mostly — the lumber industry standardized on board feet over a century ago. The math is identical to cubic feet × 12, but the unit is sized to match what a working board actually looks like, which makes pricing intuitive. A cubic foot of cherry sounds abstract; 12 board feet of cherry is roughly one nice 4/4 plank.
- Does this work for metric?
- Board feet are a North American unit. If you're working in metric, convert: 1 board foot ≈ 0.00236 cubic metres, or 2,360 cubic centimetres. Most metric markets price hardwood by the cubic metre or by the piece, not by the board foot. For metric volume math, use the Volume Calculator instead.
- How much should I order — exact or with overage?
- Always order overage. Standard practice is 15-20% extra for hardwood projects because you'll cut around knots, splits, sapwood streaks, and grain mismatches. For a project that needs 100 bdft of usable wood, order 115-120 bdft. Some yards mark boards 'shorts' or 'shop grade' at a discount if you can use them — worth asking.
- Is my data saved?
- No. The calculation runs entirely in your browser. Nothing is sent to a server, logged, or stored.
