Board foot calculator FAQ
Short answers to what people ask about board feet: the unit, the formula, quarters, nominal and actual size, boards under an inch, and what this calculator does and does not do.
What is a board foot?
The Wood Handbook defines it as: “A unit of measurement of lumber represented by a board 12 in. long, 12 in. wide, and 1 in. thick or its cubic equivalent.” That is 144 cubic inches of wood. The formula.
How do you calculate board feet?
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. Multiply by the number of boards for the total. The formula, step by step.
How many board feet are in a 2x4?
It depends on the length. Counted at its name, 2 by 4 inches, a 2x4 is 5.33 board feet at 8 feet, 6.67 board feet at 10 feet, 8 board feet at 12 feet, 10.67 board feet at 16 feet. The wood measures 1½″ by 3½″, but board measure uses the nominal size. Board foot chart.
How many board feet are in a 1x6x8?
4 board feet, counted at 1 by 6 inches and 8 feet.
What does 4/4 mean in lumber?
Hardwood thickness is called in quarters of an inch. 4/4 is 1 inch, 5/4 is 1.25 inches and 8/4 is 2 inches. What 4/4 means.
Do I use the nominal or the actual size?
The Wood Handbook says: “In practice, the board foot calculation for lumber 1 in. or more in thickness is based on its nominal thickness and width and the actual length.” For a store 2x4 that means 2 by 4 inches. A tape on the wood would give 1½″ by 3½″. The calculator counts the nominal size by default, and one button counts what you measured. Nominal vs actual sizes.
Why doesn't a 2x4 measure 2 by 4 inches?
The American Softwood Lumber Standard says: “The label designation for lumber size categories that does not reflect the dressed size. The nominal size is greater than the dressed size i.e., a dry 2 by 4 is surfaced to 38.1 mm by 88.9 mm (1 1/2 by 3 1/2 inches)” Common sizes, dry and green.
How do you count a board thinner than 1 inch?
As 1 inch. The Wood Handbook: “Lumber with a nominal thickness of less than 1 in. is calculated as 1 in.” A ½-inch board 12 inches wide and 8 feet long is 8 board feet.
How do you work out the cost of lumber by the board foot?
Multiply the board feet by the price per board foot. 4 board feet at $10.69 a board foot is $42.76. The calculator rounds the money once, to the cent. Worked examples.
Can I type fractions of an inch?
Yes. Type 1.75, 1 3/4 or 1-3/4 for inches, 8/4 for a hardwood thickness in quarters, and 10, 10.5 or 10 ft 6 in for a length. Use a point for decimals, not a comma.
How much waste should I add?
That depends on the boards and the job, and this page does not suggest a number. In the calculator's list you can add a waste allowance from 5% to 50% in steps of 5%, and it shows the board feet and the cost with it.
Does it work in metric?
No. The calculator takes inches and feet.
Is it the same as the app?
The numbers are. It runs a port of the Board Foot Calculator iPhone and iPad app's engine, and a test compares the two on over a hundred thousand inputs and requires every figure and sentence to match. The app also saves your prices by wood and thickness, keeps your lists, and sends a list to the yard as a text.
What does this calculator leave out?
It counts lumber you can measure. It does not scale logs, grade hardwood or apply any grading rule, and it does not convert board feet to cubic metres.
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.