Board foot calculator
Type a board’s thickness, width and length and get its board feet and its cost. It takes 8/4, 1 1/2 or a store 2x4 as you would write them. Add each board to a list and the total stays at the foot. It is free and runs in your browser.
Hardwood, in quarters
Store sizes
1 in thick · 4/46 in wide8 ft long1 board
4board feet
1 in × 6 in × 8 ft ÷ 12
Board feet = thickness (in) × width (in) × length (ft) ÷ 12, × the count. It is a port of the Board Foot Calculator app’s engine, checked against the app’s own code. The list is kept on this page only.
What a board foot is
A board foot is a unit of lumber. The USDA Forest Products Laboratory’s Wood Handbook defines it:
A unit of measurement of lumber represented by a board 12 in. long, 12 in. wide, and 1 in. thick or its cubic equivalent. [Wood Handbook, Glossary, p. G-2]
That is 12 × 12 × 1 = 144 cubic inches of wood.
How the calculator counts a board
- Thickness and width are the nominal ones; the length is the actual one. [Wood Handbook, Glossary, p. G-2] The Wood Handbook’s glossary says the board foot calculation is based on nominal thickness and width and the actual length for lumber 1 inch or more thick.
- A board under 1 inch counts as 1 inch. [Wood Handbook, Glossary, p. G-2] A half-inch board 12 inches wide and 8 feet long is 8 board feet that way.
- A store size counts at its name. [PS 20-20, section 2.2] [PS 20-20, section 2.16] A 2x4 is counted as 2 by 4 inches, though the wood measures less. One button counts what you measured instead. See nominal vs actual sizes.
- Money is counted in whole cents, once, from the unrounded board feet, so a long list never drifts a penny.
What you can type
Thickness and width take inches as a decimal (1.75), a fraction (1 3/4 or 1-3/4) or, for thickness, a hardwood quarter call (8/4, which is 2 inches). Length takes feet (10, 10.5) or feet and inches (10 ft 6 in or 10' 6"). The calculator reads 3/4 as three quarters of an inch; a quarter call starts at 4/4. The price is optional.
Use a point for decimals, not a comma. The list is kept on this page only, and nothing you type is sent anywhere.
- The formula. Thickness × width × length ÷ 12, which size to use, and how to go backwards.
- Worked examples. Nine boards and a short list, worked out step by step.
- 4/4, 8/4 and quarters. 4/4 is 1 inch, 8/4 is 2: every standard hardwood thickness, rough and planed.
- 2x4 actual size. A dry 2x4 is 1½ by 3½. Nominal and dressed sizes, dry and green.
- Board foot chart. Board feet by width and length, and for the store sizes.
- FAQ. Short answers, and what the calculator leaves out.
Take the tally to the yard in Board Foot Calculator!
For iPhone and iPad. Works offline.
This calculator is a port of the app’s engine, run in your browser and checked against the app’s own code. The app keeps the whole tally: every board you add lands on a list with its board feet and cost and the total in view, your own prices are saved by wood and thickness and fill in when you pick the wood, and the list goes to the yard as a text.
Coming soon to the App Store
How this was checked
The numbers on this page come from a port of the Board Foot Calculator iPhone and iPad app’s engine, and an automated test compares them with the app’s own code on well over a hundred thousand inputs (last run ). Statements about lumber are quoted from the USDA Forest Products Laboratory’s Wood Handbook and the American Softwood Lumber Standard, linked where they appear. Your lumberyard’s ticket is what you pay, so ask how it counts a board. If something here is wrong, tell us at a@noshu.net.