Board Foot Calculator
Add every board on your list and get the exact board footage, a waste allowance and an estimated cost — in inches, feet or metric, with fractions and 4/4 quarter sizes read as written.
Units apply to every board in the list. Thickness accepts decimals, fractions and hardwood quarter sizes such as 4/4, 5/4 and 8/4.
The formula
A board foot is a unit of volume: 144 cubic inches of wood. That is a piece one inch thick, twelve inches wide and twelve inches long. With every dimension in inches and Q identical boards:
board feet = (T × W × L × Q) ÷ 144 all dimensions in inches
Lumber lengths are usually quoted in feet, so the version most people carry around has the twelve inches per foot already divided out:
board feet = (T × W × L_ft × Q) ÷ 12 T and W in inches, L in feet
They are the same equation. This calculator converts everything to inches first and always divides by 144, so inches, feet, centimetres and metres all take one code path rather than one each.
Waste and cost then follow from the total:
board feet to buy = board feet × (1 + waste% ÷ 100) estimated cost = board feet to buy × price per board foot
The cost is charged on the waste-adjusted figure, not the raw total, because the offcuts are wood you still have to pay for.
Worked examples
One board
A board one inch thick, eight inches wide and eight feet long:
1 in × 8 in × 8 ft ÷ 12 = 5.33 board feet or, working in inches: 1 × 8 × 96 ÷ 144 = 5.33 board feet
Ten boards
Ten boards, each one inch thick, six inches wide and eight feet long:
1 in × 6 in × 8 ft × 10 ÷ 12 = 40 board feet
Waste and cost
Those forty board feet, with a ten percent waste allowance, at eight dollars per board foot:
40 × 1.10 = 44 board feet to buy 44 × $8 = $352.00 estimated
The waste allowance is the part worth thinking about rather than accepting. Forty board feet of clean, surfaced stock cut into long parts might genuinely need ten percent. The same forty board feet of rough lumber, cut into short parts that have to match across a panel, can need twice that.
What a board foot actually measures
A board foot measures how much wood there is, not how far it reaches or how much surface it covers. Any dimensions multiplying to 144 cubic inches are one board foot, so all of these are the same quantity of lumber:
- 1 in × 12 in × 12 in
- 2 in × 6 in × 12 in
- 1 in × 4 in × 36 in
- 3/4 in × 8 in × 24 in
That is why hardwood is priced this way. A yard selling by the board foot charges the same for a given volume of a species whether it arrives as one wide plank or three narrow ones.
Quarter thicknesses, and nominal versus surfaced
Hardwood thickness is written in quarters of an inch, and spoken that way too — 4/4 is “four quarter”, not “four fourths”.
| Written | Nominal | Typical surfaced (S2S) |
|---|---|---|
| 4/4 | 1 in | 13/16 in |
| 5/4 | 1 1/4 in | 1 1/16 in |
| 6/4 | 1 1/2 in | 1 5/16 in |
| 8/4 | 2 in | 1 3/4 in |
| 12/4 | 3 in | 2 3/4 in |
The surfaced column is approximate and varies by supplier. The point of the table is the gap between the two middle columns: you are normally billed on the nominal figure. Buy 4/4 walnut, take delivery of boards measuring 13/16 in, and the tally still counts them as a full inch, because the mill sawed and dried a full inch before surfacing it away.
So enter 4/4 — not 0.8125 — when you are checking a hardwood order. Type it into the thickness field and the calculator confirms how it read the size. If you want the true volume of wood you physically received instead, enter the thickness you measured.
Dimensional softwood works the same way for a different reason. A “2×4” actually measures about 1 1/2 in by 3 1/2 in, but it is tallied and priced at 2 by 4.
Choosing a waste allowance
The calculator starts at ten percent because it is a common default, not because it is correct for your project. Nothing about your cut list is known to it.
- Around 10% — surfaced, clean stock; parts that fit the boards you are buying without much ripping to width.
- 15–20% — rough lumber you have to joint and plane; some sapwood or knots to cut around; parts of varied length.
- 25–30% or more — grain or colour matching across a panel; short parts cut from long boards, where the offcuts are unusable; curved parts nested out of straight stock; a species you have not worked before.
Two things push the number up more than people expect: defects you cannot design around, and short parts. A run of 14-inch parts from 8-foot boards leaves an awkward remainder on every board, and those remainders add up fast.
Board feet, square feet and linear feet
Three different questions, and mixing them up is expensive.
- Linear feet measure length only. Twelve linear feet of 1×4 and twelve linear feet of 2×12 are very different amounts of wood.
- Square feet measure face area and ignore thickness. Useful for flooring, sheet goods and anything sold by coverage.
- Board feet measure volume, thickness included. Useful for rough and surfaced hardwood, which is sold by the amount of wood rather than by coverage.
For one-inch stock, board feet and square feet of face happen to be numerically equal, which is exactly why the two get confused. Move to 8/4 stock and a square foot of face becomes two board feet — the area is unchanged and the bill doubles.
Frequently asked questions
What is a board foot?
A board foot is a unit of volume equal to 144 cubic inches — a piece one inch thick, twelve inches wide and twelve inches long. It is how hardwood is bought and sold, because it prices the actual amount of wood rather than how far it reaches.
Any combination of dimensions multiplying to 144 cubic inches is one board foot: 1 in × 12 in × 12 in, 2 in × 6 in × 12 in, and 1 in × 4 in × 36 in are all the same quantity of lumber.
How do I calculate board feet?
Multiply thickness by width by length, with every measurement in inches, then divide by 144. Multiply by the number of identical boards.
Because lumber lengths are usually quoted in feet, the shortcut most people use is thickness in inches × width in inches × length in feet ÷ 12. It is the same equation with the twelve inches per foot already divided out — use whichever matches the numbers in front of you.
Is a board foot the same as a square foot?
No, and the difference matters when you are paying. A square foot measures area and ignores thickness. A board foot measures volume and includes it.
For one-inch stock the two happen to line up: a square foot of face on a 1 in board is one board foot. Double the thickness and the area is unchanged while the board footage doubles — a square foot of face on 2 in stock is two board feet. Linear feet are different again: they only describe length, so they say nothing about how much wood you are getting until you also know the thickness and width.
How many board feet are in a 2×4?
It depends on the length, and on whether you count nominal or actual dimensions. An eight-foot 2×4 counted at its nominal size is 2 × 4 × 8 ÷ 12 = 5.33 board feet.
A 2×4 does not actually measure two inches by four inches — surfaced softwood finishes at about 1 1/2 in by 3 1/2 in, which would be 3.5 board feet. Dimensional softwood is normally tallied and priced by its nominal size, so 5.33 is usually the figure a yard means. If you need the real volume of wood, enter the actual dimensions instead.
Should I use nominal or actual dimensions?
Use whichever your supplier bills on, and ask if you are not sure. For hardwood, board footage is normally calculated on the rough thickness before surfacing, so 4/4 stock counts as a full inch even though it arrives at about 13/16 in. For dimensional softwood, the nominal 2× and 4× sizes are the ones on the invoice.
This calculator uses exactly the numbers you type. Enter nominal figures to match a supplier's tally, or actual measured figures if you want the true volume of wood you are getting.
What does 4/4 lumber mean?
It is thickness written in quarters of an inch. 4/4 is one inch, 5/4 is one and a quarter, 6/4 is one and a half, 8/4 is two inches, and 12/4 is three. Say it as "four quarter", not "four fourths".
The number refers to the rough thickness the board was sawn to, before it was dried and surfaced. Surfaced 4/4 usually measures nearer 13/16 in, but it is still sold as 4/4 and tallied as a full inch. You can type quarter sizes straight into the thickness field above and the calculator will confirm how it read them.
How much waste should I add?
There is no single right figure. Ten percent is a reasonable starting point for straightforward cuts out of clean, surfaced stock. Rough lumber with sapwood, knots and checks can easily need twenty to thirty percent, and work where the grain has to match across a panel — or where the parts are short and the offcuts unusable — can need more.
Think about your actual cutting layout rather than reaching for a percentage. Long parts from short boards waste more than short parts from long ones, and one wide panel glued from narrow stock wastes more than a design that takes boards as they come.
How is rough lumber measured?
Rough hardwood is usually measured after drying and before surfacing, using the National Hardwood Lumber Association rules. Those rules compute a surface measure from the board's width and length and then apply rounding — widths commonly to the nearest inch, lengths to the foot — with the details varying by grade.
This calculator does not apply those rounding conventions. It multiplies the numbers you enter and divides by 144, which is transparent and reproducible but will not always match a graded tally to the decimal. That is a deliberate choice: quietly applying one mill's convention would make the figure look more authoritative than it is.
Can I calculate board feet from metric measurements?
Yes. Choose centimetres or millimetres for thickness and width, or centimetres and metres for length, and the calculator converts to inches before applying the formula — a board foot is defined in inches, so that conversion has to happen somewhere.
For reference, one board foot is 2,359.74 cubic centimetres, and one cubic metre is about 423.8 board feet.
Why might a lumberyard's tally differ from this calculator?
Several reasons, and none of them mean somebody made a mistake. Yards may measure rough rather than surfaced dimensions, round each board's width or length before multiplying, apply grading rules that treat part of a board differently, set minimum billable widths, or tally a whole lift at once rather than board by board.
Use this figure to plan a purchase and check an invoice is in the right neighbourhood. If it matters to the dollar, ask the supplier how they tally before you order.
Method and limitations
How the figure is produced. Every dimension is converted to inches, multiplied together with the quantity, and divided by 144. Rows are summed at full precision and rounded only for display — per-board figures to three decimal places, totals to two. Nothing is rounded before the total is computed.
What is not applied. No hardwood grading convention is used. National Hardwood Lumber Association rules round surface measure and width in ways that vary by grade and by mill, so applying one of them silently would make this number look more authoritative than it is while being wrong for most suppliers. The arithmetic here is plain and reproducible; where a graded tally differs, the tally governs the invoice.
What this cannot tell you. Whether a species is right for the job, whether a board will be stable once it is cut, what a supplier's minimum billable width is, how a yard rounds, or whether the price you entered is a fair one. It is an estimating tool for planning a purchase and sanity-checking an invoice.
Your measurements stay in the browser. There is no account, no database, and nothing about your project is sent anywhere.