Woodworking Board Feet

How Board Feet Are Calculated

A board foot is the standard lumber-industry volume unit — 144 cubic inches, the volume of a 1”x12”x12” board. Enter your board’s thickness, width, length, and quantity to find the total board footage and, if you know a price per board foot, the estimated cost.

Board feet is the unit hardwood and specialty lumber is priced by — unlike the common softwood dimensional lumber sold at a home center (a “2x4” priced by the linear foot), a hardwood supplier typically quotes a price per board foot and expects you to work out your own total from a board’s actual dimensions. This calculator does that math for you, whether you’re pricing a single board or a whole order of identical pieces.

Key Factors to Consider

• Nominal and actual lumber dimensions are usually different. A board sold as “1x6” doesn’t actually measure 1 inch by 6 inches — it’s typically closer to 3/4” x 5.5” once dried and planed. Use the ACTUAL measured dimensions of your lumber, not its nominal sold size, for an accurate board-foot count.
• Rough-sawn lumber is usually sold at its true, un-planed thickness. Hardwood is often sold rough-sawn (e.g. “4/4” meaning roughly 1 inch thick before planing) rather than pre-surfaced — check whether your supplier quotes thickness before or after planing, since planing removes material and reduces the final board footage.
• This calculates raw material volume, not usable yield after cutting and waste. Real woodworking projects lose some material to cutting, defects, and waste — order some extra board footage beyond the exact calculated amount for a project with many cuts or a lot of joinery.
• Board feet is a volume measurement, unrelated to a board’s linear length by itself. A short, thick, wide board and a long, thin, narrow board can have the identical board-foot volume — don’t assume two boards with the same board-foot count are interchangeable for a project that needs a specific length or width.

Common Mistakes

• Measuring width or thickness in feet instead of inches. The board-foot formula expects thickness and width in inches and length in inches too (or a length-in-feet variant that divides by 12 instead of 144) — mixing units into the same formula without converting first will give a result off by a factor of 12.
• Forgetting the quantity multiplier. A single board’s board footage is easy to get right, but it’s just as easy to price only one board and forget to multiply by how many identical pieces you’re actually ordering.
• Treating “board feet” as a price, not a volume. Board feet measures volume, not cost — the same board-foot total can cost very different amounts depending on species and grade (see Useful to Know below). Don’t assume a board-foot figure from one species or supplier translates directly to a price from another.
• Assuming rough-sawn thickness is the finished thickness. If your supplier’s price is quoted on rough-sawn (“green” or unplaned) stock, the board actually delivered may be thinner once it’s surfaced — ask whether the quoted thickness is before or after planing if the exact finished dimension matters for your project.

The Formula

$$\text{Board Feet} = \frac{\text{Thickness} \times \text{Width} \times \text{Length (in)}}{144} \times \text{Quantity}$$

Worked Example

1. $\frac{1 \times 6 \times 96}{144} \times 4 = 16 \text{ bf}$

Useful to Know

Board-foot price varies a lot by grade, not just species. Hardwood lumber is typically sold under a grading system (such as FAS, Select, and the “Common” grades) that rates a board mainly by how much clear, defect-free material it yields — a higher grade costs meaningfully more per board foot than a lower one of the identical species, because more of the board can be used without cutting around knots, checks, or other defects. If you’re comparing quotes or estimating cost, make sure the price-per-board-foot figure you enter here reflects the grade you’re actually buying, not just the species name.