Case 1
- Thickness
- 1in
- Width
- 6in
- Length
- 8ft
4.0000bd ft
Open with these valuesBoard Foot Calculator
4.0000bd ft
Result: 4.0000 bd ftA board foot is 144 cubic inches: a board 1 inch thick, 12 inches wide and 1 foot long. Multiply thickness in inches by width in inches by length in feet, then divide by 12. A rough 1×6 board 8 feet long is 4 board feet.
The numbers at a glance
Held fixed: Thickness 1.000 in, Width 6.000 in.
| Length (ft) | Result (bd ft) |
|---|---|
| 2.000 | 1.0000 |
| 4.000 | 2.0000 |
| 6.000 | 3.0000 |
| 8.000Your value | 4.0000 |
| 10.000 | 5.0000 |
| 12.000 | 6.0000 |
| 14.000 | 7.0000 |
| 16.000 | 8.0000 |
Worked examples
Case 2
- Thickness
- 0.75in
- Width
- 5.5in
- Length
- 10ft
3.4375bd ft
Open with these valuesCase 3
- Thickness
- 2in
- Width
- 12in
- Length
- 16ft
32.0000bd ft
Open with these valuesHow it's calculated
bd ft = (T × W × L) ÷ 12
- StepEnter thickness and width in inches — the two small dimensions.
- StepEnter length in feet, not inches; this is where the ÷ 12 comes from.
- ResultFor rough-sawn stock use the full sawn size, for planed stock the actual size.
What this number means
A board foot is the unit hardwood and rough-sawn timber are bought and sold in. It is exactly 144 cubic inches: the wood in a board one inch thick, twelve inches wide and one foot long. Despite the name it measures volume, not length or area, which is why a thick plank holds more board feet than a thin board of the same face size. The calculation multiplies thickness by width by length and divides by 12. That divisor reconciles the mixed units — thickness and width in inches, length in feet — because a foot is twelve inches. A board 1 inch thick, 6 inches wide and 8 feet long gives (1 × 6 × 8) ÷ 12 = 4 board feet. Multiply that by the piece count to size a whole order, and use it to compare prices between yards that quote differently. The caveat that matters most is nominal versus actual size. Rough-sawn hardwood is usually billed at its nominal dimensions, but planed softwood is smaller than its name: a 2×4 is really about 1.5 by 3.5 inches. Decide which you are using before you start, keep the length in feet, and remember this is volume only — no allowance for cuts, defects or waste.
It is a volume, despite the name
A board foot is exactly 144 cubic inches. That is why a thick plank holds more board feet than a thin board of the same face size.
Nominal is not actual
Rough-sawn hardwood is usually billed at nominal dimensions, but planed softwood is smaller than its name — a 2×4 is about 1.5 by 3.5 inches. Decide which you are using before you start.
Where the divisor 12 comes from
Thickness and width are in inches while length is in feet, and a foot is twelve inches. The 12 reconciles the mixed units, nothing more.
Commonly misread
Board feet tell me how much timber to order.
They tell you the volume of the finished pieces. Cuts, defects and waste are not in the number — add your own allowance on top.
Two boards with the same face size cost the same.
Only if they are the same thickness. Double the thickness and you double the board feet, and with them the price.
Reference table
| T, W, L | Typical piece | Board feet |
|---|---|---|
| 0.75, 5.5, 10 | planed 1×6, 10 ft | 3.4375 |
| 1, 6, 8 | rough 1×6, 8 ft | 4 |
| 1, 12, 1 | one board foot by definition | 1 |
| 1.5, 7.25, 8 | planed 2×8, 8 ft | 7.25 |
| 2, 6, 10 | rough 2×6, 10 ft | 10 |
| 2, 12, 16 | rough 2×12, 16 ft | 32 |
| 3, 10, 12 | timber 3×10, 12 ft | 30 |
Questions
What is a board foot?
A board foot is a unit of volume used to measure and price lumber, equal to 144 cubic inches. It is the amount of wood in a board 1 inch thick, 12 inches wide and 1 foot long. Despite the word foot, it measures volume — not length or area.
How do I calculate board feet?
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A board 1 in thick, 6 in wide and 8 ft long is (1 × 6 × 8) ÷ 12 = 4 board feet.
Why do you divide by 12?
Because the formula mixes units: thickness and width are in inches but length is in feet. One board foot is 144 cubic inches and a foot converts to 12 inches, so 144 ÷ 12 = 12 inch-inch-feet make one board foot.
Should I use nominal or actual lumber size?
It depends on how the wood is sold. Rough-sawn hardwood is measured at its full sawn size, so a 1 in × 6 in board uses 1 and 6. Planed softwood is smaller than its name — a 2×4 is really about 1.5 in × 3.5 in — so use the actual size for a true volume.
What is the difference between board feet and square feet?
Square feet measure area and ignore thickness, while board feet measure volume and include it. Flooring and sheet goods are sold by the square foot; rough lumber and hardwood by the board foot, because a thicker board holds more wood for the same surface.
How many board feet are in a 2×4?
Using the nominal size, an 8-foot 2×4 is (2 × 4 × 8) ÷ 12 = 5.3333 board feet. Priced from the actual planed dimensions of 1.5 in × 3.5 in it works out to 3.5 board feet, which is why the basis matters.
Sources and last check
Information, not professional advice.