What Is a Board Foot?
A board foot is a unit of lumber volume - 144 cubic inches, the wood in a piece one inch thick, a foot wide and a foot long. Here is what that means, how it differs from a linear, square and cubic foot, and how to convert it to cubic metres.
By the Calculate My Reno Team / Published
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A board foot is a unit of lumber volume: 144 cubic inches of wood. Picture a board 1 inch thick, 12 inches wide and 1 foot long - that is one board foot. Any piece with the same volume counts the same, whether it is thick and narrow or thin and wide.
Why lumber is sold this way
Because a board foot is a volume, it captures thickness, width and length together. That lets a sawmill price a thick, wide plank and a thin, narrow one on the same scale - by how much actual wood is in each. It is the standard unit for hardwood and rough-sawn lumber, and the figure on a “price per board foot” tag.
Work it out
The volume is easy to find from the size:
board feet = thickness_in × width_in × length_ft ÷ 12
A full walk-through is in how to calculate board feet, or just use the board foot calculator. Remember to use the nominal size - a 2x4 is figured 2 by 4, not its actual 1½ × 3½.
Board foot vs linear foot vs square foot
These three get mixed up constantly because they measure different things:
| Unit | Measures | Counts |
|---|---|---|
| Linear (lineal) foot | Length | Just how long the board is |
| Square foot | Area | Length × width |
| Board foot | Volume | Length × width × thickness |
Ten linear feet of 1x6 and ten linear feet of 1x4 are the same length but not the same amount of wood - the 1x6 is more board feet. Use linear feet when a board is priced by length, board feet when it is priced by volume.
Board foot vs cubic foot and cubic metre
A board foot is a small volume, so it converts cleanly to the bigger units:
| 1 board foot equals |
|---|
| 144 cubic inches |
| 1/12 cubic foot (so 12 board feet = 1 cu ft) |
| ≈ 0.00236 cubic metres |
| ≈ 2.36 litres |
Going the other way, 1 cubic metre ≈ 423.8 board feet and 1 cubic foot = 12 board feet. That matters if your supplier sells timber by the cubic metre but you think in board feet, or vice versa - the board foot calculator shows both at once.
A board foot of spray foam
Spray foam insulation is also sold in board feet, and it means the same 144 cubic inches: one square foot covered at 1 inch thick. A 1,000 board-foot kit covers 1,000 sq ft at 1 inch, or 500 sq ft at 2 inches - the depth is what eats the board feet.
In short
- A board foot is 144 cubic inches of wood - a 1 in × 12 in × 1 ft piece.
- It is a volume, unlike a linear foot (length) or square foot (area).
- 12 board feet = 1 cubic foot, and 1 m³ ≈ 423.8 board feet.
Frequently asked questions
What is a board foot?
A board foot is a unit of lumber volume equal to 144 cubic inches - the wood in a board 1 inch thick, 12 inches wide and 1 foot long, or any piece with the same volume. It is how sawmills and hardwood dealers measure and price lumber, because it captures thickness, width and length all at once.
What is a board foot of lumber equivalent to?
One board foot equals 144 cubic inches, which is 1/12 of a cubic foot, about 0.00236 cubic metres, or about 2.36 litres of wood. Twelve board feet make one cubic foot, and one cubic metre is about 423.8 board feet.
What is the difference between a board foot and a linear foot?
A linear (or lineal) foot is just length - one foot of a board, whatever its size. A board foot is a volume that also counts thickness and width. Ten linear feet of 1x6 is more wood than ten linear feet of 1x4, but they are the same number of linear feet. Use linear feet when a board is sold by length and board feet when it is sold by volume.
What is a board foot of spray foam?
In spray foam insulation a board foot is the same 144 cubic inches - one square foot of area covered at 1 inch thick. So 1,000 board feet of foam covers 1,000 sq ft at 1 inch, or 500 sq ft at 2 inches. It is the same volume idea as lumber, just applied to coverage depth.
Is a board foot the same as a square foot?
No. A square foot is area - length times width, with no thickness. A board foot is volume - it adds the thickness. One board foot happens to be one square foot of wood at 1 inch thick, which is where the two get confused.