Board Foot Calculator – One Board Size, Then the Whole Project List
Lumber is sold by volume, not by the piece — and that volume has a name: the board foot. Start with one board size here, then add a row for every other size to build the whole project list, with its total board feet and cost.
Counting one size in bulk instead? Board Feet Calculator tallies one board size by quantity — the same volume maths, a different job: one size, counted in bulk, rather than a mixed-size project list.
One board size
Nominal size quick-fill (fills in the actual size)
Waste allowance
🔒 Everything is calculated in your browser — your project list never leaves your device.
Your board feet
The count, step by step
Cost note: the estimate prices the amount you actually buy — the total including your waste allowance. At the default 0% waste, 80 board feet at $5.50 is $440.00.
Build the whole lumber list
Real projects mix sizes — decking boards, joists, a few posts. Add a row for each size below: every row gets its own board feet and cost, and the list keeps the project total for you. This is the list you take to the yard.
Lumber is sold by volume, not by the piece — and that volume has a name: the board foot. Enter the thickness, width and length of your boards and get board feet per piece, the project total, a waste allowance and the full cost, with the working shown. The trade’s two quiet traps are handled too: nominal sizes that are not the size they claim, and hardwood thickness sold in quarter inches.
Key takeaways
- A board foot is honest volume, so measure the board you will actually hold.
- Add a row for each size below: every row gets its own board feet and cost, and the list keeps the project total for you.
- A 2×4 measures 1.5 × 3.5 inches — the quick-fill buttons above use the real numbers.
How it works, in 3 steps
Measure actual, not nominal
A board foot is honest volume, so measure the board you will actually hold: thickness and width with a tape or caliper, length in feet and inches. A 2×4 measures 1.5 × 3.5 inches — the quick-fill buttons above use the real numbers.
Multiply, then divide by 144
Thickness × width × length in inches gives cubic inches; one board foot is exactly 144 of them. Short on inches? With the length in feet the same formula divides by 12 instead.
Add waste, then price it
Multiply by your pieces, add a waste allowance for cuts and defects, and price the buy-total at your yard’s rate per board foot. The number you pay for is the number with waste on it.
The maths behind a board foot
Length 8 ft = 96 in
The default board, worked through. A board 2 inches thick, 6 inches wide and 8 feet long holds 2 × 6 × 96 = 1,152 cubic inches. Divide by 144 and you get exactly 8 board feet per piece. Ten pieces make 80 board feet, which is 80 ÷ 12 = 6.67 cubic feet of wood, and at $5.50 per board foot the stack costs $440.00 before any waste allowance.
Why 144? A board foot is defined as the volume of a board one inch thick, twelve inches wide and twelve inches long: 1 × 12 × 12 = 144 cubic inches. Every board-foot figure is just “how many of those fit in your board” — which is why the formula is one multiplication and one division, and why a 1 × 12 board exactly one foot long is precisely 1 board foot.
The feet shortcut. Because 144 ÷ 12 = 12, you can skip the inch conversion when the length is a whole number of feet: thickness × width × length in feet, divided by 12. The calculator accepts feet plus odd inches, converts to inches internally, and always divides by 144 — one method, no rounding surprises.
Deep dives
Nobody at the lumberyard is lying to you — the name is a souvenir. A century ago a 2×4 really was sawn a full 2 inches by 4 inches, green and rough. Modern boards are dried in a kiln, which shrinks the wood, then planed smooth on all four faces (what the trade calls S4S), which trims it again. Standards settled where they settled: a finished 2×4 measures 1.5 × 3.5 inches, roughly a quarter of its named cross-section simply gone. The name stuck because carpenters needed one word for the stud, not a measurement.
| Nominal size | Actual size (in) | Board feet in an 8 ft board |
|---|---|---|
| 1×4 | 0.75 × 3.5 | 1.75 BF |
| 1×6 | 0.75 × 5.5 | 2.75 BF |
| 1×8 | 0.75 × 7.25 | 3.63 BF |
| 2×4 | 1.5 × 3.5 | 3.5 BF |
| 2×6 | 1.5 × 5.5 | 5.5 BF |
| 2×8 | 1.5 × 7.25 | 7.25 BF |
| 2×10 | 1.5 × 9.25 | 9.25 BF |
| 2×12 | 1.5 × 11.25 | 11.25 BF |
| 4×4 | 3.5 × 3.5 | 8.17 BF |
| 6×6 | 5.5 × 5.5 | 20.17 BF |
Why it matters for board feet. Price a 2×4 by its name and you would calculate 5.33 board feet for an 8-footer; the board in your hand holds 3.5. Construction lumber is usually priced by the piece, which hides the gap, but hardwood is priced by the board foot — and there the gap is money. Hardwood adds its own wrinkle: quarters are measured on the rough board, so a 4/4 board you pay a full board foot for may plane down to 13/16 of an inch thick. Rule of thumb: pay by the system the yard uses, design by the size you measure, and when a number really matters, put a tape on the actual board.
Waste is not carelessness — it is geometry. Boards come in fixed lengths and your project does not, so ends get trimmed; knots and splits get cut out; a miscut happens to everyone. Straightforward framing or decking wastes about 5 to 10 percent. Furniture work wastes more, 10 to 15 percent, because you are selecting for grain and colour, not just size. Anything diagonal — herringbone floors, chevron tabletops — can waste 20 percent, because every angled end throws away a triangle of good wood. Buy the waste on purpose, with the chips above, instead of discovering it on a Sunday afternoon.
What the price per board foot is really telling you. The same species can double in price between grades: a clear, straight-grained board costs more per board foot than a common-grade board full of knots, because more of it is usable. Thickness costs too — 8/4 stock is usually pricier per board foot than 4/4 of the same species, since thick, clear boards grow on fewer trees. Before you commit, run your project at the yard’s actual price here; sometimes stepping down a grade and adding 5 percent more waste allowance is the cheaper build.
Picking boards. Sight down each board like a rifle: bow, cup and twist are visible in two seconds and miserable forever. For wide boards, prefer several narrower ones glued up over one very wide board — wide stock cups more and costs more per board foot. And check the ends: checks and splits at the butt mean you will trim 2 to 4 inches before you start, which is exactly what your waste allowance is for.
Board feet, square feet, cubic feet and linear feet: converting between them
Four units describe the same pile of lumber, and each one answers a different question. A board foot is a volume: 144 cubic inches. A cubic foot is also a volume, and it holds exactly 12 board feet, because 1,728 cubic inches divided by 144 is 12. A square foot is an area: the face of the board, with no thickness in it. A linear foot is a length: one foot of one board, whatever its width. The conversions between them need the thickness and width, because volume is area times thickness, and a square foot of 2-inch stock holds twice the wood of a square foot of 1-inch stock.
The three conversions worth memorising are these. Board feet to cubic feet: divide by 12. Square feet to board feet: multiply the area by the thickness in inches, because board feet equal thickness in inches times area in square feet. Board feet to linear feet: multiply the board feet by 12, then divide by thickness in inches times width in inches, because one linear foot of a board holds thickness times width times 12 cubic inches. Worked on a real order: 100 square feet of decking in 5/4 by 6 boards, finished 1 inch thick and 5.5 inches wide, needs 100 board feet before waste, and 100 times 12 divided by 5.5, or about 218 linear feet of board. Add the waste allowance before ordering, not after, because the waste boards are bought at the same price as the good ones.
| From | To | Rule |
|---|---|---|
| Board feet | Cubic feet | Divide by 12 |
| Square feet | Board feet | Multiply by thickness in inches |
| Board feet | Linear feet | Multiply by 12, divide by thickness times width in inches |
| 1-inch board | Square feet | 1 board foot covers 1 square foot |
Nominal size vs actual size: why the same 2×6 gives two different answers
A 2×6 is not 2 inches by 6 inches. The name is the size of the rough-sawn board before drying and planing; the board you buy is smaller, typically 1.5 inches by 5.5 inches for softwood. Run the formula on the name and an 8-foot 2×6 holds 8 board feet. Run it on the board itself and the same piece holds 5.5 board feet. Both answers are honest, and they answer different questions: the nominal figure is what a yard may quote, and the actual figure is the wood in your hands. The gap matters most when you are comparing prices, because a price per board foot computed on nominal dimensions looks cheaper than the same price computed on actual dimensions, for identical wood.
The quarter system in the quick-fill chips works the same way. A 4/4 board is named for 1 inch, a 5/4 board for 1.25 inches, a 6/4 board for 1.5 inches and an 8/4 board for 2 inches, all rough-sawn, all thinner once finished. This calculator uses the actual dimensions you enter, which is the right basis for working out how much wood a project contains. When a supplier quotes by the board foot, ask which dimensions the quote uses before comparing it with another yard. A quote that looks 10 percent cheaper on nominal dimensions and a quote that looks 10 percent dearer on actual dimensions can be the same price for the same boards, and the only way to tell is to ask.
Board foot questions, answered
What is a board foot?
A board foot is a unit of lumber volume used across North America: the volume of a board 1 inch thick, 12 inches wide and 12 inches long — exactly 144 cubic inches. Lumber is priced by the board foot because it charges fairly for the wood itself, whatever shape it is cut into: a short thick board and a long thin one can hold the same amount of timber. This calculator turns any thickness, width and length into board feet with one formula: (thickness × width × length in inches) ÷ 144.
How do I calculate board feet?
Multiply the thickness in inches by the width in inches by the length in inches, then divide by 144. If the length is in feet, multiply thickness × width × feet and divide by 12 instead — the same answer. Example: a 2 × 6 board 8 feet long is (2 × 6 × 96) ÷ 144 = 8 board feet. For several boards, multiply the per-piece figure by the number of pieces, then add a waste allowance before you buy.
Why is a 2×4 not actually 2 inches by 4 inches?
The name is nominal — it describes the rough-sawn size the board started as, not the finished size you take home. Before a 2×4 reaches the shelf it is dried, which shrinks it, and planed smooth on all four sides, which trims it further. What remains measures 1.5 × 3.5 inches. The pattern runs through softwood lumber: a 2×6 finishes at 1.5 × 5.5, a 2×8 at 1.5 × 7.25. Because a board foot is real volume, always calculate with the actual measured size — the quick-fill buttons on this page do exactly that.
What do 4/4, 5/4, 6/4 and 8/4 lumber mean?
Hardwood thickness is sold in quarters of an inch, measured on the rough board before surfacing: 4/4 (said “four-quarter”) is 1 inch rough, 5/4 is 1.25 inches, 6/4 is 1.5 inches and 8/4 is 2 inches. After a board is planed smooth on both faces (sold as S2S), it comes out thinner — 4/4 typically finishes at 13/16 of an inch. When you plan a project, the quarters figure is what you pay for; the surfaced figure is what you design with. The thickness chips on this page enter the quarter sizes directly.
How much extra lumber should I buy for waste?
For straight cuts and simple work, 5 to 10 percent extra covers trimming, end cuts and the odd defective board. Furniture and mixed-grain projects usually deserve 10 to 15 percent, because you will reject boards for colour and grain as much as for size. Diagonal layouts, herringbone patterns and first attempts at a new joint can eat 20 percent or more. Pick an allowance with the chips above and the calculator prices the total you actually buy, waste included.
How many board feet are in a cubic foot?
Exactly 12. A cubic foot is 1,728 cubic inches and a board foot is 144 cubic inches, and 1,728 ÷ 144 = 12. The rule runs both ways: divide board feet by 12 for cubic feet. It is handy for comparing a lumber quote against firewood, veneer or shipping volumes quoted in cubic feet — like the 80 board feet in the example on this page, which is 6.67 cubic feet of wood.
How many board feet are in a square foot?
It depends on the thickness. One board foot is 144 cubic inches, so a square foot of 1-inch stock is exactly 1 board foot, a square foot of 2-inch stock is 2 board feet, and a square foot of half-inch stock is half a board foot. Multiply the area in square feet by the thickness in inches to get board feet.
How do I convert board feet to linear feet?
You need the thickness and the width as well as the board feet. Multiply the board feet by 12, then divide by the thickness in inches times the width in inches. One linear foot of a board holds thickness times width times 12 cubic inches, so a wider or thicker board gives fewer linear feet from the same number of board feet.
Should I calculate board feet from nominal or actual dimensions?
Use the actual dimensions of the boards you will buy when working out how much wood a project contains, because the finished board is thinner and narrower than its name. Use the same basis as the supplier when comparing prices, and ask which basis a quote uses. A price per board foot on nominal dimensions and the same price on actual dimensions are different prices for the same wood.
Related calculators
Counting one size in bulk? See the Board Feet Calculator — one board size tallied by quantity.
Estimates for planning — measure the boards you actually buy.
Finished lumber sizes follow North American standards, but mills, species and moisture content vary, and hardwood sold by the board foot is measured rough, before surfacing. Prices per board foot change with species, grade and region, so treat the cost here as a planning figure and confirm it against your yard’s current list. Nothing on this page sizes structural lumber for a load — beams, joists and spans follow your local building code and, where it matters, an engineer’s stamp, not a volume estimate.
A board foot is the wood itself — count it in actual inches and the count will never lie to you.
↑ Back to top