How to use the lumber and board foot calculator
- Pick a Common size such as 2x4, or choose Custom size and type the Nominal thickness (in) and Nominal width (in) yourself.
- Enter the Length per board (ft) and the Number of boards.
- Type a Price ($, optional) and set The price is to per board, per board foot or per linear foot, matching the tag or the yard's quote.
- Read the board feet, the linear feet and the total cost. The cost box also converts your price into the other two units, so you can compare a per-board tag against a per-board-foot quote.
How board feet are worked out
A board foot is a piece of wood 12 inches wide, 12 inches long and 1 inch thick, or 144 cubic inches. The formula is thickness (in) x width (in) x length (ft) / 12. The University of Wisconsin-Extension explains it in What Is A Board Foot?, which also points out that the result uses nominal sizes, not the true volume. Linear feet are simply length times the number of boards. Typical actual sizes shown by the tool come from the American Softwood Lumber Standard (PS 20), summarized in the Southern Pine Inspection Bureau's size guide.
Worked example with the default inputs
Ten 2x4s, each 8 ft long, at $8 per board. Each board is 2 x 4 x 8 / 12 = 5.33 board feet, so ten boards are 53.33 board feet and 80 linear feet. At $8.00 a board the total is $80.00, which works out to $1.50 per board foot and $1.00 per linear foot. The wood itself is 1.5 x 3.5 inches, so each board really holds 3.50 board feet, but you are billed for 5.33.
Limits and edge cases
- The tool does not add waste. Order extra boards for cuts, knots and mistakes.
- Hardwood is usually sold in quarters of an inch. Enter 1 for 4/4, 1.25 for 5/4 and 2 for 8/4, and measure the rough size you are buying.
- A yard may round each board or the whole order to a convenient board foot figure, so a quote can differ slightly from this total.
- Typical actual size only appears for standard softwood sizes. Planing, drying and the yard's stock can change it.
- Need to convert a measurement like 1.5 in? Use the decimal to fraction converter or the length converter. Building a deck? The concrete calculator sizes the footings.
Frequently asked questions
How many board feet are in a 2x4?
A 2x4 holds 0.667 board feet for every foot of length (2 x 4 / 12). An 8-foot 2x4 is 5.33 board feet, a 10-foot is 6.67 and a 12-foot is 8.00.
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 1x8 that is 8 feet long is 1 x 8 x 8 / 12 = 5.33 board feet.
Does a board foot use nominal or actual size?
For softwood sold as dimension lumber, yards bill by nominal size, so a 2x4 counts as 2 by 4 inches even though it measures 1.5 by 3.5. For an exact wood volume, enter the actual size instead.
What is the difference between a board foot and a linear foot?
A linear foot is one foot of length at any size. A board foot is a volume of 144 cubic inches. A 2x4 and a 2x12 of the same length have the same linear feet, but the 2x12 has three times the board feet.
Sources: University of Wisconsin-Extension, What Is A Board Foot? (No. 42); Southern Pine Inspection Bureau, Nominal vs Actual Lumber Sizes (PS 20).