Framing and carpentry
Board foot calculator
A board foot is a volume, and for softwood it is billed on a size the board does not have. That gap is the whole reason a tape measure never agrees with an invoice.
Written and edited by Pablo Ruiz Quintero
Last reviewed 2026-09-17 · Nothing you type leaves your browser
The boards
Softwood is billed on the nominal size and hardwood in quarters of an inch of the rough board. They are different systems giving the same unit, which is most of the confusion.
Nominal sizes: a 2 × 4 bills as 2 by 4 and measures 1 1/2 by 3 1/2.
Item 1
Standard framing lumber. Sold by the piece everywhere, and the board-foot figure is only useful for comparing sizes or estimating a truckload.
Used only to pick a regional labour rate. It stays in your browser.
Board feet
106.67
20 pieces · 160 linear ft · 175 lb
Billed for 52 % more wood than is there
106.7 board feet on the nominal size against 70 of actual timber. It is a convention, not a surcharge — but it is why measuring a board never agrees with the invoice.
Item by item
| Board | Each | Total bf | Weight |
|---|---|---|---|
| 20 off 2 × 4 × 8 ft | 5.333 | 106.67 | 175 lb |
What it costs
National average. Material only, at the board foot. Delivery, cutting and any milling are separate.
$0.90 a board foot. This species is sold by the piece at every yard, so treat the figure as a way of comparing sizes rather than as a quote. A framed structure gives you the cut list to put in here.
Scaling a log
How many board feet come out of a log depends on which rule the mill uses, and the three in common use do not agree.
Inside the bark, at the thin end.
Scaled in whole 4 ft sections.
| Rule | Per log | Total | What it is |
|---|---|---|---|
| Doyle | 144 | 144 | The simplest and the commonest in the eastern United States. It assumes 4 in of slab waste regardless of log size, which is roughly right on a big log and wildly punitive on a small one. |
| Scribner | 166 | 166 | Drawn from diagrams of boards sketched into circles rather than from a formula, then tabulated. It sits between the other two and is the rule most western mills and the Forest Service use. |
| International 1/4 in | 200 | 200 | The only one derived from geometry rather than custom, with a 1/4 in saw kerf and a half-inch-per-four-feet taper allowance. It is the most accurate and the one a seller asks for. |
The same log, three rules, 39 % apart. Doyle counts the least and the International 1/4 in rule the most, and the gap widens as logs get smaller — on a 16 in log it is 39 %. This is not an academic difference: which rule the mill uses is the single biggest variable in what a load of logs is worth, and it is agreed before the truck arrives, not after.
Worth knowing
- Board feet here are worked out on the NOMINAL size, which is how softwood is billed: a 2 × 4 counts as two inches by four even though it measures 1 1/2 by 3 1/2. That is not an error and nobody is overcharging — it is a convention left over from when boards were measured rough, before planing. It does mean the billed volume is about 52 % more than the wood you can actually put a tape on.
- SPF (spruce-pine-fir) is sold by the piece, not by the board foot. The figure above is still worth having for two things: comparing sizes honestly, and knowing whether the load fits in the vehicle.
- 175 lb in 20 pieces, worked out from the ACTUAL dimensions rather than the nominal ones, because an axle does not care about billing conventions. A half-ton pickup is rated for about 1,000–1,500 lb of payload with nothing else in it.
On this page — 8 sections
- 01A volume, not a length — and billed on a size that is not there
- 02How much you are billed for that is not there
- 03Hardwood counts in quarters, and it counts the rough board
- 04What it weighs, and whether it fits in the vehicle
- 05Three rules, one log, and up to half the difference
- 06Five ways this goes wrong
- 07How the calculator works it out
- 08The words on a lumber ticket
A volume, not a length — and billed on a size that is not there
The short version
- A board foot is 144 cubic inches. Thickness × width × length ÷ 144, or ÷ 12 with the length in feet.
- Softwood bills on the nominal size. A 2 × 4 counts as 2 by 4 and measures 1.5 by 3.5.
- Hardwood uses quarters of rough thickness. Different system, same unit, endless confusion.
- Weight comes from the actual size. Treated lumber weighs nearly double dry framing.
The board foot is the oldest unit still in daily use in construction, and the most misunderstood — not because the arithmetic is hard, but because of what goes into it.
The arithmetic is one line. The confusion is that for dimensional softwood the numbers you put into it are the size the board is called, not the size it is. A 2 × 4 is billed as two inches by four, and measures 1.5 by 3.5. So every board foot you pay for contains about two thirds of a board foot of wood.
board feet = (thickness × width × length in inches) ÷ 144
- thickness, width
- the NOMINAL size for softwood; rough thickness in quarters over actual width for hardwood
- length
- in inches — or use ÷ 12 with the length in feet, which is the version that gets done in the head
- 144
- cubic inches in a board foot: 1 × 12 × 12
Worked through — A 2 × 4 × 8 ft: 2 × 4 × 8 ÷ 12 = 5.33 board feet. Twenty of them is 106.7 board feet — and about 70 board feet of actual timber, weighing 175 lb.
National Institute of Standards and Technology, Voluntary Product Standard PS 20, American Softwood Lumber Standard · checked 2026-09-17
How much you are billed for that is not there
Planing takes a fixed amount off a board — half an inch off the width up to seven inches, three quarters above that, and a quarter off the thickness of a one-inch board. Being fixed, it costs proportionally far more on small stock than on large.
| Called | Actually | Bf per linear ft | Note |
|---|---|---|---|
| 1 × 2 | 0.75 × 1.5 | 0.167 | |
| 1 × 4 | 0.75 × 3.5 | 0.333 | |
| 1 × 6 | 0.75 × 5.5 | 0.500 | |
| 1 × 8 | 0.75 × 7.25 | 0.667 | From 8 in up the loss is 3/4 in, not 1/2. It is the step people get wrong. |
| 1 × 10 | 0.75 × 9.25 | 0.833 | |
| 1 × 12 | 0.75 × 11.25 | 1.000 | |
| 2 × 2 | 1.5 × 1.5 | 0.333 | |
| 2 × 4 | 1.5 × 3.5 | 0.667 | The most quoted dimension in construction, and neither number is right. |
| 2 × 6 | 1.5 × 5.5 | 1.000 | |
| 2 × 8 | 1.5 × 7.25 | 1.333 | |
| 2 × 10 | 1.5 × 9.25 | 1.667 | |
| 2 × 12 | 1.5 × 11.25 | 2.000 | |
| 4 × 4 | 3.5 × 3.5 | 1.333 | |
| 4 × 6 | 3.5 × 5.5 | 2.000 | |
| 6 × 6 | 5.5 × 5.5 | 3.000 | Timbers 5 in and over lose only 1/2 in, so a 6 × 6 is 5 1/2 and not 5 1/4. |
Hardwood counts in quarters, and it counts the rough board
Walk into a hardwood yard and nothing above applies. Thickness is given in quarters of an inch of the rough board — 4/4, 5/4, 8/4 — and width is whatever that particular board happens to be, because hardwood is not ripped to standard widths. You are buying timber, not a product.
The trap is the same one in a different place. You pay for 4/4 and receive 0.8125 in surfaced two sides, because the planing comes out of what you bought. A project needing a full inch of finished thickness has to start at 5/4.
| Called | Rough | Surfaced 2 sides | What comes out of it |
|---|---|---|---|
| 4/4 | 1 in | 0.8125 in | One inch rough, 13/16 surfaced two sides. The default board. |
| 5/4 | 1.25 in | 1.0625 in | What a stair tread or a thick shelf comes out of. |
| 6/4 | 1.5 in | 1.3125 in | Table aprons and heavier frames. |
| 8/4 | 2 in | 1.75 in | Table legs, and where the price per board foot starts climbing. |
| 12/4 | 3 in | 2.75 in | Rare, ordered, and priced accordingly. |
| Dimensional softwood | Hardwood | |
|---|---|---|
| Billed on | Nominal size | Rough thickness in quarters |
| Width | Standard, one of a dozen | Whatever the board is |
| Sold by | The piece | The board foot |
| Lengths | Even feet, 8 to 16 | Random, and you buy the whole board |
| Surfaced | Always, four sides | Rough or two sides, usually |
| Grading | Structural — what it can carry | Appearance — how much clear face it has |
National Hardwood Lumber Association, Rules for the Measurement and Inspection of Hardwood and Cypress · checked 2026-09-17
What it weighs, and whether it fits in the vehicle
Weight is where using the nominal size stops being harmless. A truck axle does not care about billing conventions, and the difference between the two sizes is thirty per cent of the load.
The other half of the problem is that pressure-treated lumber leaves the yard wet. The preservative is waterborne and a fresh board is carrying several pounds of it — at 50 lb a cubic foot against 30 for kiln-dried framing, the same stack of boards weighs nearly two thirds more.
52%
Billed above actual
on a 2 × 4
0.667
Bf per linear ft
of 2 × 4, worth memorising
50
lb per ft³ treated
against 30 dry
39%
Log rule spread
on a 16 in log
Before loading it
- Payload from the door-jamb sticker, not the towing rating — they are different numbers and the small one is the one that matters.
- Treated lumber weighed wet. It will be lighter in three months and you are carrying it today.
- Weight worked out from actual dimensions, which is about 30 per cent less than the nominal ones would suggest.
- Long stock supported at both ends, not cantilevered off a tailgate, or it takes a set and stays bent.
- Anything over 16 ft is a delivery, not a pickup load, whatever it weighs.
- Treated lumber kept off dry interior stock — it is wet and it will stain and swell what it touches.
The deck calculator sizes joists, beams and posts and gives you the piece count to bring back here for the volume, the weight and the load.
Need the cut list first?Three rules, one log, and up to half the difference
Turning a standing log into a board-foot figure is not arithmetic, it is a choice of convention — and the three conventions in common use disagree enormously. The same 16 in log, 16 ft long, is 144 board feet by Doyle, 166 by Scribner and 200 by the International quarter-inch rule.
The disagreement is not random. Doyle assumes four inches of slab waste whatever the log measures, which is roughly right on a large log and punitive on a small one — on a ten-inch log it counts barely half of what the International rule does. Which is why a buyer likes Doyle and a seller asks for International, and why the rule is agreed before the truck arrives rather than after it is loaded.
| Rule | What it does |
|---|---|
| Doyle | The simplest and the commonest in the eastern United States. It assumes 4 in of slab waste regardless of log size, which is roughly right on a big log and wildly punitive on a small one. |
| Scribner | Drawn from diagrams of boards sketched into circles rather than from a formula, then tabulated. It sits between the other two and is the rule most western mills and the Forest Service use. |
| International 1/4 in | The only one derived from geometry rather than custom, with a 1/4 in saw kerf and a half-inch-per-four-feet taper allowance. It is the most accurate and the one a seller asks for. |
USDA Forest Service, Log scaling rules: Doyle, Scribner and the International 1/4-inch rule · checked 2026-09-17
Five ways this goes wrong
01Using actual dimensions for board feet on softwood
It gives a number about 34 per cent under what the yard will bill, which turns a comparison between two quotes into nonsense.
Instead — Nominal for dimensional softwood, always. Use actual sizes for design and for weight, never for the invoice.
02Ordering 4/4 hardwood for a one-inch finished part
4/4 surfaces to 0.8125 in, and if it needs flattening from rough there is less again. The part ends up thin or the board ends up scrap.
Instead — Start at 5/4 for anything that has to finish at a full inch.
03Comparing a per-piece price against a per-board-foot price
They are different units and the sizes differ, so the comparison is meaningless without converting. This is how a dear quote looks cheap.
Instead — Convert everything to one unit first. Divide a piece price by the board feet in that piece.
04Estimating a truckload from nominal size
It overstates the volume by a third, and if the lumber is treated it understates the weight by more than that in the other direction. The two errors do not cancel.
Instead — Actual dimensions times density, and treated lumber weighed wet.
05Selling logs without agreeing the scale
Doyle against International on a small-log load is a difference of nearly half the value, and the scaling is done after the logs have left.
Instead — Agree the rule, and who scales, before anything moves. Put it in writing for anything beyond a trailer load.
How the calculator works it out
- 01Decide which system appliesDimensional softwood is billed on the nominal size. Hardwood is billed in quarters of rough thickness over the actual width.
- 02Multiply thickness by width by lengthIn inches, then divide by 144. If the length is in feet, multiply thickness by width by length and divide by 12 instead.
- 03Multiply by how many piecesBoard feet add up straight, unlike sheet goods, which is the one convenience of the unit.
- 04Convert to the price you were quotedHardwood is quoted per board foot. Softwood is quoted per piece, so divide the piece price by the board feet in it to compare.
- 05Work the weight from the actual sizeNever from the nominal one. Volume times density, and treated softwood is far heavier than it looks because it leaves the yard wet.
- 06For logs, agree the rule before the truckDoyle, Scribner or International. Which one is used changes the answer by up to half.
Nominal against actual dimensions come from the American Softwood Lumber Standard. The quarter system, surface measure and the rough-versus-surfaced thicknesses come from the hardwood grading rules. The three log formulas and the taper allowance come from the Forest Service. Densities and prices are a survey. All of it is on the sources page, dated.
One thing stated plainly, because it is the whole point of the page: volume is computed on the billing size and weight on the actual size. They are deliberately different numbers, and any tool that uses one figure for both is wrong in one of the two answers.
Nothing you type is sent anywhere — the whole thing runs in your browser.
The words on a lumber ticket
Two are worth knowing before ordering: what nominal means, and what quarters mean. Between them they account for nearly every argument at a lumber counter.
- Board foot
- 144 cubic inches of lumber — one inch thick, twelve inches wide, twelve inches long, or anything that multiplies to the same. It is a volume, not a length and not an area.
- Nominal size
- The size a board is called and billed as. A 2 × 4 is nominally two by four inches and actually 1.5 by 3.5, a gap of 52 per cent by volume.
- Actual size
- What a tape measure finds: the dressed dimension after the board has been planed on all four sides. It is what you design with and never what you pay by.
- Quarters
- How hardwood thickness is expressed — quarters of an inch of the rough board. 4/4 is one inch, 8/4 is two, and after surfacing you receive noticeably less than either.
- Surface measure
- Width times length in square feet, taken on the rough board at the yard. Multiply by the thickness in quarters and you have the board feet you are charged for.
- S2S and S4S
- Surfaced two sides — planed on the faces, rough on the edges — or surfaced four sides. Hardwood is usually sold rough or S2S and you straighten the edges yourself.
- Linear foot
- Length alone, with no reference to section. It is how dimensional softwood is actually sold, which is why a board-foot price on framing lumber is a comparison and not a quote.
- Log rule
- A formula converting a log's small-end diameter and length into the board feet it will yield. Three are in common use and they disagree by up to half on the same log.
- Doyle rule
- The commonest in the eastern United States, and the one that counts least. It assumes four inches of slab waste whatever the log size, which is about right on a big log and severe on a small one.
- International 1/4 in rule
- The only rule derived from geometry rather than custom, with a quarter-inch saw kerf and a taper allowance. The most accurate, and the one the person selling the logs asks for.
- Slab
- The rounded offcut taken off the outside of a log before any square lumber comes out of it. How much a rule assumes gets slabbed off is the difference between the three.
- Taper
- A log is wider at the butt than at the top, so it holds more than its small-end diameter suggests. Only the International rule accounts for it, at half an inch per four feet.
Common questions
- How do you calculate board feet?
- Thickness in inches times width in inches times length in inches, divided by 144. With the length in feet it is thickness times width times length divided by 12, which is the version people carry in their heads. A 2 × 4 × 8 is 2 × 4 × 8 ÷ 12 = 5.33 board feet.
- Do you use nominal or actual size for board feet?
- Nominal, for dimensional softwood — that is the convention and every yard in the country bills that way. It means the number is about 52 per cent larger than the wood you can measure with a tape on a 2 × 4. Hardwood is the exception: it uses the rough thickness in quarters over the board's real width, because hardwood is not ripped to standard widths in the first place.
- Why is a 2 × 4 not 2 by 4 inches?
- Because it was, once, when it left the saw rough. Then it gets dried and planed on four sides and comes out 1.5 by 3.5. The name stayed because changing it would invalidate every span table, every price list and every builder's intuition at the same time. It is not a deception — it is standardised in writing, and the actual dimensions are the ones in the code book.
- How many board feet in a 2x4?
- 5.33 in an eight-footer, 6.67 in a ten and 8 in a twelve — 0.667 board feet per linear foot of 2 × 4. That last figure is the useful one to remember, because it converts a cut list straight into board feet.
- What does 4/4 mean in lumber?
- Four quarters of an inch of rough thickness, so one inch. It is how hardwood is graded and priced, and the catch is that 4/4 surfaced two sides comes out at 0.8125 in — you pay for an inch and receive thirteen-sixteenths. If a project needs a full inch finished, order 5/4.
- How much does a board foot of lumber cost?
- It depends entirely on the species. Framing softwood works out around $0.90 a board foot, poplar about $4, red oak $6.50 and walnut $15. Softwood is not actually sold that way — it is priced per piece — so use the figure to compare sizes rather than to place an order.
- How much does lumber weigh?
- Volume times density, and the volume is the actual size rather than the nominal one. Kiln-dried framing runs about 30 lb a cubic foot, so a 2 × 4 × 8 is around 9 lb. Pressure-treated southern pine is 50 lb a cubic foot fresh from the yard, because the preservative is waterborne — a treated 2 × 6 × 12 is about 34 lb, and thirty of them is a thousand pounds.
- How many 2x4s fit in a pickup?
- Payload is the limit, not space. A half-ton pickup is typically rated for 1,000 to 1,500 lb with nothing else aboard, which is about 120 kiln-dried 2 × 4 × 8s — or roughly 40 treated 2 × 6 × 12s, because treated lumber weighs nearly twice as much. The sticker in the door jamb has the real number, and it is much lower than the towing figure people remember.
- How many board feet are in a log?
- It depends which rule you ask. A 16 in log 16 ft long gives 144 board feet by Doyle, 166 by Scribner and 200 by the International 1/4 in rule — the same log, 39 per cent apart. Doyle assumes a fixed four inches of slab waste whatever the size, so it penalises small logs hardest: on a 10 in log it counts nearly half of what the International rule does.
- Which log rule is most accurate?
- The International 1/4 in rule, and it is not close. It is the only one derived from geometry — a quarter-inch saw kerf and a half-inch taper allowance per four feet — rather than from custom or a tabulated diagram. Which rule gets used is a matter of local practice and of who has the stronger hand, and it is agreed before the load moves.
- Is a board foot the same as a linear foot?
- No, and they are not convertible without knowing the section. A linear foot is length. A board foot is volume. Sixteen linear feet of 1 × 4 is 5.33 board feet; sixteen linear feet of 2 × 12 is 32. Yards quote framing per piece, decking per linear foot and hardwood per board foot, all on the same site.
- Does plywood come in board feet?
- No. Sheet goods are sold by the sheet or by the square foot, because the thickness is fixed within a product and volume adds nothing. Board feet apply to solid lumber, where thickness genuinely varies from board to board.
Send this to whoever is paying
The link carries your measurements, so whoever opens it sees the same numbers you are looking at — and you can come back to it yourself tomorrow with the delivery note in front of you.
Plain links, no tracking scripts. Nothing here reports back that you shared it.
About the author
Pablo Ruiz Quintero — Editor
Editor of MaterialsEstimator. Decides which documents count as a source, what every default value is, and where the line sits between what the reader parses and what the engines compute.
More about how this site is edited