How do you calculate board feet?

Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. If the length is in inches instead of feet, divide it by 12 first to convert it, then run the same formula — the two routes always agree, since dividing by 12 twice is the same as dividing by 144 once. For several identical boards, find the board feet in one and multiply by the count: five 1×6 boards at 10 ft each come to 5.00 × 5 = 25.0 board feet.

How many board feet in a 2x4x8?

5.33 board feet, using the nominal size a 2×4 is sold by: 2 × 4 × 8 ÷ 12 = 5.33. If you instead measure the actual, dressed board — 1.5 in × 3.5 in — the true volume is only 3.50 board feet. Yards and mills invoice on the nominal figure, so 5.33 is the number that shows up on the receipt.

Is a board foot the same as a linear foot?

No. A linear foot only measures length and ignores thickness and width entirely, while a board foot is a volume that accounts for all three dimensions. A 8 ft 2×4 and a 8 ft 2×12 are both 8 linear feet, but the 2×4 is only 5.33 board feet against 16.0 board feet for the 2×12 — three times as much wood in the same length. Pricing lumber by the linear foot only makes sense once the width and thickness are fixed, which is why dimensional framing lumber is sometimes priced that way but hardwood almost never is.

How much does a board foot of lumber cost?

It depends heavily on species. Construction softwoods (pine, fir, spruce) typically run $0.60 – $1.50 per board foot, while a common furniture hardwood like red oak runs $5 – $9 and a premium species like black walnut can reach $9 – $16. At a mid-range $4.50 per board foot, an 8 ft 2×4 (5.33 board feet) costs about $24. A $200 budget at $4 per board foot buys 50.0 board feet — enough for 9 boards that size, spending $192 once the count is rounded down to a whole board.

What does 4/4 lumber mean?

Hardwood is graded and priced by rough thickness stated in quarters of an inch rather than a fraction: 4/4 ("four-quarter") means 1 in thick before surfacing, 8/4 means 2 in, and 12/4 means 3 in. After planing on both faces, a 4/4 board typically finishes around 13/16 in — noticeably thinner than the 1 in the quarter-count implies, the same nominal-versus-actual gap that dimensional softwood lumber has.

How many board feet in a 2x6?

It depends on length, but a nominal 2×6 works out to exactly 1.00 board foot per linear foot, since 2 × 6 ÷ 12 = 1. That makes the length the whole answer: an 8 ft 2×6 is 8.00 board feet, a 12 ft 2×6 is 12.0 board feet, and so on — one of the few sizes where the board-foot count and the length in feet are the same number.

Nominal vs actual lumber size — what's the difference?

Nominal size is the name a board is sold under (2×4, 2×10…) and the size used to calculate and price its board feet. Actual size is what it measures after milling and drying, which runs about 1/4 to 3/4 in smaller on each face — a nominal 2×4 is actually 1.5 in × 3.5 in, and a nominal 2×10 is actually 1.5 in × 9.25 in. The gap exists because rough-sawn lumber is planed smooth and dried after the nominal size is assigned, and both steps shrink the board without changing what it's called or how it's charged.

Construction

Board Foot Calculator

A board foot is 144 cubic inches of lumber: (thickness in × width in × length ft) ÷ 12. Pick a nominal size or enter your own dimensions to get total board feet and cost for any number of boards — or flip it around and solve for how many boards a budget affords.

Board size

Dimensions to use

Lumber is priced by its nominal, sold size — switch to actual only to size the real, dressed board in your hands.

Thickness

WidthHardwood is sold in quarters — 4/4 = 1 in, 8/4 = 2 in

Length

How many boards?

Pricing

Price per board foot

$/ bd ft

Board feet

5.33 bd ft

2 in × 4 in × 8 ft ÷ 12

Per board

5.33 bd ft

Boards

Estimated material cost

$24

5.33 bd ft @ $4.50 / bd ft

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One board foot = 144 in³ of lumber. Board footage is conventionally figured on nominal size, the size lumber is sold and priced by.

The basics

What a board foot measures

Board feet exist because lumber is priced and stocked as a volume, not a length. Two boards of the same length can hold very different amounts of wood, and the board foot is the single number that captures the difference.

T × W × L ÷ 12

One board foot is 144 cubic inches

A board one foot square and one inch thick holds exactly one board foot. Multiply thickness and width in inches by length in feet and divide by twelve, and any size of board reduces to the same unit.

2 × 4 × 8 ÷ 12 = 5.33 bd ft

2×4 ≠ 1.5 × 3.5 in

Nominal size vs actual size

A board named 2×4 is milled and dried down to roughly 1.5 in × 3.5 in, but it is still sold, stocked and board-footed under its nominal name. Board-foot math runs on nominal size unless you deliberately choose otherwise.

Nominal: 5.33 bd ft · Actual: 3.50 bd ft

Method

How to calculate board feet by hand

Four steps take a tape-measure reading to an order, whether you are pricing boards or working backwards from a budget.

1
Note the nominal size the lumber is sold by
Use the thickness and width stamped on the tag — 2×4, 2×6 and so on — not the smaller actual, dressed size. A yard prices by the nominal figure even though the board is milled smaller.
2×4 → thickness 2 in, width 4 in
2
Put the length in feet
The formula runs on length in feet. A length quoted in inches or metres has to be converted first, or the answer lands off by a factor of twelve or more.
96 in ÷ 12 = 8 ft
3
Multiply thickness × width × length, then divide by 12
With thickness and width in inches and length in feet, the product is a cubic-inch count per foot of length; dividing by twelve converts it into board feet.
2 × 4 × 8 ÷ 12 = 5.33 bd ft
4
Multiply by quantity, then apply price — or invert for a budget
Multiply one board's figure by the number of boards for the total, then by a price per board foot for cost. To go the other way, divide a budget by the price to get affordable board feet, then divide by one board's figure and round down.
$200 ÷ $4.00 = 50.0 bd ft

Worked examples

The same method across three sizes

A 2×4, a 1×6 and a 2×6, each at the lengths a yard actually stocks — every figure below computed by the calculator's own logic, not typed in by hand.

Given: 2×4 nominal, 8 ft long

Multiply: 2 × 4 × 8 ÷ 12

Evaluate: 5.33 bd ft

Given: 2×4 nominal, 10 ft long

Multiply: 2 × 4 × 10 ÷ 12

Evaluate: 6.67 bd ft

Given: 2×4 nominal, 12 ft long

Multiply: 2 × 4 × 12 ÷ 12

Evaluate: 8.00 bd ft

Given: 2×4 nominal, 16 ft long

Multiply: 2 × 4 × 16 ÷ 12

Evaluate: 10.7 bd ft

Where it shows up

Why board feet matter

Three places a board-foot figure decides real money, from a framing takeoff to a sawmill's log scale.

framing takeoffs

Estimating a framing package

Studs, joists and rafters are priced and quoted in board feet once a takeoff totals up every piece on a plan, so a framing estimate is really a very long board-foot addition problem.

per-board-foot pricing

Woodworking and furniture stock

Hardwood for furniture, cutting boards and cabinetry is sold by the board foot rather than by the piece, since boards come in irregular widths and lengths that a per-piece price cannot fairly capture.

stumpage and log scale

Sawmills and timber sales

Standing timber and sawlogs are valued in board feet using a log scale that estimates the lumber a log will yield, which is the board-foot idea applied before the tree is even cut.

Reference

Nominal vs actual, and board feet per 8 ft board

The dimensions every board-foot calculation depends on, and the board-foot count for one standard 8 ft length of each size — the length most often quoted in examples and price lists.

Nominal size	Actual size	Board feet per 8 ft board
1×4	0.75 × 3.5 in	2.67
1×6	0.75 × 5.5 in	4.00
2×4	1.5 × 3.5 in	5.33
2×6	1.5 × 5.5 in	8.00
2×8	1.5 × 7.25 in	10.7
2×10	1.5 × 9.25 in	13.3
2×12	1.5 × 11.25 in	16.0
4×4	3.5 × 3.5 in	10.7

Quick chart

Board feet by size and length

The answer to “how many board feet in a 2×8×12” and every variation of it — every common nominal size at the lengths a yard typically stocks, computed on nominal dimensions.

Size	8 ft	10 ft	12 ft	16 ft
1×4	2.67	3.33	4.00	5.33
1×6	4.00	5.00	6.00	8.00
2×4	5.33	6.67	8.00	10.7
2×6	8.00	10.0	12.0	16.0
2×8	10.7	13.3	16.0	21.3
2×10	13.3	16.7	20.0	26.7
2×12	16.0	20.0	24.0	32.0
4×4	10.7	13.3	16.0	21.3

Figures are exact board feet per single board — multiply by quantity for a full order.

Hardwood

Pricing lumber in quarters

Hardwood swaps the framing world's nominal sizes for a rough thickness stated in quarters of an inch, and its per-board-foot price swings far more with species than softwood's does.

Quarter	Rough thickness
4/4	1 in
5/4	1.25 in
6/4	1.5 in
8/4	2 in
10/4	2.5 in
12/4	3 in
16/4	4 in

Species	Per bd ft
Construction pine, fir & spruce (SPF)	$0.60 – $1.50
Cedar	$3 – $7
Poplar	$3 – $6
Red oak	$5 – $9
Hard maple	$6 – $10
Black walnut	$9 – $16

8/4 stock costs roughly twice as much per board foot to buy as 4/4 of the same species, since it is genuinely twice the volume — the quarter system is a thickness label, not a separate pricing scale.

Common mistakes

Where board-foot estimates go wrong

Four errors account for almost every board-foot number that looks plausible and is wrong by a clean multiple.

÷ 144, not ÷ 12

Dividing by twelve instead of a hundred forty-four

A board foot is a cubic measure, not a linear one — a board one foot square and one inch thick. Multiplying three inch-dimensions and stopping at a division by twelve leaves the wrong units, unless the length was already converted to feet first.

sold by nominal

Pricing off the actual, dressed size

A yard measures and prices by the nominal size stamped on the tag, even though the board in your hand is smaller. Board-footing the actual, planed-down size understates what the mill and the invoice both call the same piece of lumber.

linear ≠ board feet

Confusing linear feet with board feet

A linear foot is only length — it says nothing about thickness or width. A ten-foot two-by-four and a ten-foot two-by-twelve are both ten linear feet, but one is three times the board feet of the other.

convert length first

Leaving a metric length unconverted

The formula wants length in feet. A board measured in metres has to be converted before it joins the multiplication, or the answer lands an order of magnitude away from the real figure.

Worth knowing

Rules worth remembering

Six facts that turn a board-foot number from a formula output into a decision you can order against.

1 ft × 1 ft × 1 in

The unit itself is a small block

A board foot is exactly 144 cubic inches — a foot square and an inch thick. Every other size of board is just some multiple or fraction of that one reference block.

nominal wins the invoice

Actual size is real, nominal size is billed

The board in your hands is smaller than its name, but the invoice, the tag and this calculator's default all run on the nominal figure — the size lumber is sold by.

8 ft 2×4: nominal 5.33 bd ft vs actual 3.50 bd ft

2×6 = 1 bd ft/ft

A few sizes reduce to round numbers

Because 2 × 6 ÷ 12 equals exactly one, a nominal 2×6's board-foot count is just its length in feet — a handy shortcut worth remembering on site.

12.0 bd ft in a 12 ft 2×6 — the length and the board-foot count match

quarters, not fractions

Hardwood thickness has its own language

4/4, 6/4, 8/4 and up describe rough thickness in quarter-inches, a convention softwood framing lumber never uses — mixing the two systems is a common source of ordering mistakes.

order 10–20% over

Waste eats into every order

Defects, warp, and the width of every saw kerf all consume board feet that never make it into a finished project — woodworkers routinely order noticeably more than the net design calls for.

grade sets usable yield

Grade changes what you can use, not the formula

A board's grade (FAS, Select, #1 Common…) predicts how much of its gross board footage is free of knots and defects — the board-foot formula counts the whole board regardless, so a lower grade means paying for board feet you will cut away.

FAQ

Common questions

A board foot is a unit of lumber volume equal to 144 cubic inches — a board one foot square and one inch thick. It exists because lumber is a three-dimensional product but gets bought by a single number, so thickness, width and length are folded into one figure: (thickness in inches × width in inches × length in feet) ÷ 12. A 2×4 that is 8 ft long comes to 2 × 4 × 8 ÷ 12 = 5.33 board feet.

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