Board foot calculator
A board foot is 144 cubic inches of wood. Enter the thickness, width, length, and quantity below to get board feet per piece and the total, and add a price per board foot to see the cost. Build a cut list to total several different boards at once.
Length used
96.0 in
8.0 ft
Board feet / piece
8.00
This board total
8.00 bf
How to calculate board feet
A board foot is a volume, not a length. One board foot is 144 cubic inches: a piece one foot long, one foot wide, and one inch thick. The formula uses inches for thickness and width and divides by 144 to convert:
Board feet = (thickness″ × width″ × length″) ÷ 144
A 2-inch by 6-inch board that is 8 feet long works out to (2 × 6 × 96) ÷ 144, which is 8 board feet. If you measure length in feet instead of inches, multiply the two other dimensions and divide by 12: (2 × 6 × 8) ÷ 12 gives the same 8 board feet. The calculator handles either length unit for you.
Reading lumber thickness: the quarter system
Hardwood is sold in quarters of an inch. The thickness is written as a fraction over four, and the top number counts quarter inches. 4/4 is four quarters, or one inch. Common sizes:
- 4/4— one inch rough
- 5/4— one and a quarter inches
- 6/4— one and a half inches
- 8/4— two inches
- 12/4— three inches
- 16/4— four inches
The quarter number is the rough-sawn thickness before the mill planes the board. That distinction drives the next point.
Nominal versus actual thickness
Rough-sawn lumber measures its full quarter thickness, so a 4/4 rough board is a full inch and is billed as a full inch. Once the mill surfaces both faces, a 4/4 board usually finishes near 13/16 inch, and a common shop planing brings it to 3/4 inch. The wood is thinner, yet you still pay for the rough inch you started with.
For board-foot math, enter the thickness the seller charges you for. Buying rough-sawn 8/4 stock means entering 2 inches even after you plane it to 1 3/4. Buying surfaced-two-sides boards means entering the surfaced thickness. Ask the seller which thickness their price applies to before you calculate.
Board feet, linear feet, and cost
A linear foot measures length alone and tells you nothing about how much wood a board holds. Board feet fold in thickness and width, which is why a 1-inch by 4-inch board and a 2-inch by 12-inch board of equal length differ by six times in board footage. Lumber priced by the board foot is priced by volume, so the same dollar figure buys far more of a thin narrow board than a thick wide one.
For turning stock, board feet also help you compare a squared blank against a slabbed piece. A 3-inch by 3-inch by 12-inch bowl blank is (3 × 3 × 12) ÷ 144, or 0.75 board feet, so a shop charging by the board foot for turning squares is easy to check against a per-piece price. Enter your price per board foot above to convert any cut list straight into a total cost.
A worked example
Say you need six 8/4 walnut boards, each 7 inches wide and 6 feet long, at $9 per board foot. Per board: (2 × 7 × 72) ÷ 144 = 7 board feet. Six boards is 42 board feet, and at $9 that is $378. Change the width to 8 inches and the total climbs to 48 board feet and $432. The calculator updates both figures the moment you change a number, and the cut list keeps a running total when your boards are not all the same size.