Key Takeaways
- A board foot is a volume measurement equal to 1 inch thick, 12 inches wide and 12 inches long
- The formula is (thickness x width x length) divided by 144, all in inches
- Lumber is sold by the board foot at hardwood yards, while softwood is sold by linear foot or per piece
- A standard 2x4 that is 8 feet long equals 5.33 board feet
- Knowing board feet helps you compare prices accurately across different lumber sizes
Board foot is a unit of volume for lumber equal to 144 cubic inches, or a board measuring 1 inch thick, 12 inches wide and 12 inches long.
Rough sawn refers to lumber that has not been surfaced or planed after cutting, retaining its full rough dimensions.
If you have ever walked into a hardwood lumber yard and heard prices quoted per board foot, you know the term matters. But most people who work with softwood dimensional lumber never use it, which is why the concept feels confusing when it first comes up.
A board foot is simply a volume measurement. It tells you how much wood you are buying, regardless of the board’s shape or size.
The formula
The standard formula is:
(board feet) = (thickness in inches x width in inches x length in inches) / 144
A board that is 1 inch thick, 8 inches wide and 96 inches long:
(1 x 8 x 96) / 144 = 5.33 board feet
The 144 in the denominator converts cubic inches into board feet because one board foot equals 144 cubic inches.
Why 144?
One board foot is defined as a volume of 1 inch x 12 inches x 12 inches, which equals 144 cubic inches. The formula divides total cubic inches by 144 to express the result in board feet.
Common boards in board feet
A 2x4 that is 8 feet long is actually 1.5 inches x 3.5 inches x 96 inches after surfacing. That works out to 4.2 board feet in its finished dimensions, but the rough sawn version before planing was 2 x 4 x 96 = 5.33 board feet. Hardwood yards price by the rough sawn dimension because that is the full volume of wood purchased.
A 1x6 that is 6 feet long in rough sawn dimensions:
(1 x 6 x 72) / 144 = 3 board feet
Board feet versus linear feet
Linear feet is a one-dimensional measurement: the length of the board regardless of width or thickness. Board feet account for all three dimensions. A 1x12 and a 1x3 that are both 8 feet long have the same linear footage but very different board foot counts.
This is why the per-board-foot price can be misleading if you do not know what you are comparing. A board foot of 4/4 (1 inch) hardwood costs less per board foot than a board foot of 8/4 (2 inch) hardwood because the thicker stock requires more raw material.
Where board feet matter
At a hardwood lumber yard, everything is priced per board foot. You pick the boards you want, the clerk measures each one, and your total is the sum of the board feet times the price per board foot.
At a home center selling softwood dimensional lumber, prices are per piece or per linear foot. A 2x4x8 has a fixed price regardless of whether the board is a little under or a little over its nominal dimensions.
The distinction matters when you are comparing costs between suppliers or when you are planning a project that requires a specific volume of wood.
Rough sawn versus surfaced
When hardwood is rough sawn, it is at its full nominal dimensions. After surfacing (planing smooth on both faces), it loses about 1/4 inch per face. A rough 4/4 board becomes about 3/4 inch thick after surfacing.
The board foot price is based on the rough sawn dimensions, which is the volume you purchased. The surfaced dimensions are what you actually work with. This is a standard part of the lumber industry, not a trick or a surcharge.
Calculating for a project
If a project calls for a specific volume of wood, add up the board feet for every piece in the cut list. For example, a dining table top made from four boards that are each 1 inch x 10 inches x 72 inches:
4 x (1 x 10 x 72) / 144 = 20 board feet
That number tells you how much lumber to request and lets you compare the total cost across different species and grades.
The board foot calculator handles the math for individual boards and project totals, converting between board feet, linear feet and actual piece counts.
Editorial note: This article is reviewed for accuracy and updated regularly. All calculations use standard lumber industry formulas. For pricing, consult your local hardwood or softwood supplier directly.
Frequently asked questions
How many board feet are in a 2x4x8?
In rough sawn dimensions, a 2x4x8 is 5.33 board feet. After surfacing to finished dimensions of 1.5 x 3.5 inches, it contains about 4.2 board feet. Hardwood yards use the rough sawn measurement.
How do you convert board feet to square feet?
Board feet and square feet measure different things. Board feet measure volume; square feet measure area. To convert, you need to know the thickness. A board foot of 1-inch thick lumber covers 1 square foot. A board foot of 2-inch thick lumber covers only half a square foot.
What is the difference between a board foot and a linear foot?
A linear foot is a length measurement: 12 inches of board regardless of width or thickness. A board foot is a volume measurement that accounts for thickness, width and length. A 1x12x12 board is 1 linear foot but 12 board feet.
Why is hardwood priced per board foot but softwood priced per piece?
Hardwood comes in varying widths and thicknesses, so board feet provide a consistent way to price different boards. Softwood dimensional lumber is manufactured to standardized sizes, so a per-piece or per-linear-foot price is simpler for both the seller and the buyer.