Work out board feet from thickness, width and length for hardwood sold by the board foot.
Quick answer: One board foot is 144 cubic inches — a piece 1 in thick, 12 in wide and 12 in long. Formula: thickness (in) times width (in) times length (ft) divided by 12. A 1 in by 6 in board 8 ft long is 4 board feet, so ten boards are 40 board feet, about $200 to $480 at $5 to $12 per board foot.
What do you have?
in
Nominal thickness — enter 1 for 4/4 stock, 2 for 8/4 stock.
in
ft
$
Hardwood commonly runs $4–$15 per board foot; construction softwood is often cheaper per board foot but sold by the piece.
Board feet
40.00
1 × 6 in, 8.0 ft
Linear feet
80
10 pieces × 8 ft
The maths
Formulathickness × width × length ÷ 12
Your entry1 × 6 × 8 ÷ 12 × 10
Board feet40.00
Cost at $8.00/bf$320
Add 10% for cutting waste on framing, and remember that nominal sizes are larger than actual sizes — if a project specifies 2×6 actual dimensions, you are buying 5-1/2 in material.
Board feet are calculated from nominal dimensions — a 2×4 is 2 in by 4 in on paper, though it actually measures 1-1/2 in by 3-1/2 in. Softwood is usually priced per piece or per linear foot; hardwood is priced per board foot.
Core facts
Formula
thickness × width × length ÷ 12
One board foot
144 cubic inches
Thickness
Written in quarters: 4/4, 6/4, 8/4
Sold by
Board foot, by species and grade
What is Board Foot Calculator?
A board foot is a volume, not a length: 144 cubic inches, or a piece one inch thick, twelve inches wide and twelve inches long. Hardwood dealers price this way because boards from the same stack can be wildly different widths. The formula is thickness in inches times width in inches times length in feet, divided by 12. Hardwood thickness is usually written in quarters: 4/4 is one inch rough, 5/4 is one and a quarter, 6/4 is one and a half and 8/4 is two inches. Surfacing removes material before you receive it, but board feet is billed on the rough quarter measure, which is why a 4/4 board is thinner than an inch when it arrives.
Common uses for Board Foot Calculator
Price a hardwood order from a yard that quotes by the board foot
Compare one wide board with two narrow boards for the same job
Convert a cut list into board feet before buying rough lumber
Check that a mill invoice matches the boards you received
Work out the board feet in a tabletop glue-up
Why hardwoods are priced by volume
Softwood framing comes in a handful of standard widths, so counting pieces works. Hardwood comes in random widths out of the same stack, and two boards of equal length may differ by four inches in width. Pricing by volume makes those boards comparable and lets a yard invoice an order without measuring every piece against a fixed schedule. That is the whole reason the board foot exists.
Quarter thickness, explained
Hardwood thickness is written in quarters of an inch of rough stock: 4/4 is one inch, 5/4 is one and a quarter, 6/4 is one and a half, and 8/4 is two inches. You are billed on that rough figure, not on what the planer leaves behind. Surfacing removes material, so a 4/4 board planed on both faces usually finishes around 3/4 in thick. Settle your final dimensions after the stock is in your hands rather than before you order it.
Grade changes the price more than size does
Two boards with identical dimensions can carry very different prices, because grade describes how much clear, defect-free face they offer. A first-and-seconds board is mostly clear; a common-grade board has knots, checks and sap. For painted work the lower grade is often fine. For a visible tabletop, pay for the clear face and buy a little extra.
Frequently Asked Questions
What exactly is a board foot?
One board foot is 144 cubic inches of wood, the same as a board one inch thick, twelve inches wide and twelve inches long. Thickness and width are measured in inches, length in feet, and the product is divided by twelve. A 1 in by 12 in by 1 ft board is one board foot.
Do I use rough or surfaced thickness?
Use the rough quarter measure the lumber is sold by. A 4/4 board counts as one inch even though a surfaced one measures about 13/16 in. Widths are normally taken as the actual width of the rough board, because hardwoods are not sold in nominal 2x4 sizes.
Why did my yard charge more than the calculator?
Species, grade and surfacing all change the price per board foot, and some yards add a fee for cutting, planing or a minimum order. Sales tax and delivery sit on top. The calculator multiplies your own price, so enter the number you were actually quoted.
How much waste should I allow for hardwood?
Ten percent is a reasonable working allowance on a straight-line project, and fifteen percent is safer on figured wood or where you need clear, defect-free faces. Hardwood is often sold in random widths, so you may not get the exact widths your plan assumes.