Lumber Calculator (Board Feet)
Calculate board feet from lumber thickness, width, length, and quantity.
How we calculate it
Board feet = (Thickness × Width × Length) / 12 × Quantity, thickness and width in inches, length in feet.
Understanding your estimate
Lumberyards price rough stock by the board foot, not by the piece count on your cut list. Tell a supplier you need ten 1x6 boards at eight feet and they still have to convert that into board feet before quoting you anything. Get that conversion wrong by hand and you either walk out short a board or two, or pay for volume the project never needed.
Ten 1x6 boards, worked out
The calculator opens with these numbers already filled in: ten boards, nominal 1 inch thick, 6 inches wide, 8 feet long.
- Thickness in feet: 1 in ÷ 12 = 0.083 ft.
- Width in feet: 6 in ÷ 12 = 0.5 ft.
- Volume of one board: 0.083 × 0.5 × 8 = 0.333 ft³.
- A board foot is defined as 1 ft × 1 ft × 1 in, which works out to 1/12 ft³, so that volume converts to 4 board feet per piece.
- Ten boards: 4 × 10 = 40 board feet, the number that goes on the order.
Check the definition against the classic textbook case: a single board 1 inch thick, 12 inches wide, and 8 feet long comes out to exactly 8 board feet. Double the width of our example and the board feet per piece doubles too, which is exactly what happens.
Why the metric toggle does nothing here
Every other calculator on this site follows the unit switcher in the header. This one ignores it on purpose. Board feet has no metric cousin that lumberyards quote by, the way our Mulch Calculator's depth field genuinely works in either inches or centimeters. There's no metric unit that stands in for a board foot the same clean way, so building a metric mode here would mean inventing a conversion nobody in the trade actually uses. This page stays in inches, feet, and board feet no matter what the rest of the site is set to, a deliberate scope decision from when the calculator shipped.
Why the result comes back exact
Our Concrete Calculator rounds bag counts up, because a bag is a whole object you either buy or you don't, and coming up short mid-pour is expensive. Board feet works differently: it's a continuous volume measurement, closer to a reading on a fuel gauge than a count of items, and the number of boards in your order was already a decision you made before opening this calculator. There's no purchase quantity here to protect with a safety margin, so the result above is the exact output of the math, decimals included.
A loose end we're leaving visible
The unit toggle in the site header still appears on this page, and clicking it leaves the result below untouched. Hiding it would mean teaching the header which calculator it's rendering next to, a bigger change than this calculator needed to justify on its own. It sits there doing nothing, a known rough edge we'd rather show you than quietly work around.
Checked against the textbook example
1 in thick, 12 in wide, 8 ft long comes out to exactly 8 board feet, the example almost every woodworking reference uses to teach the unit in the first place. This calculator's test suite checks that exact case before it checks anything more complicated, on the theory that if the textbook case doesn't come back clean, a stranger combination of dimensions has no business being trusted either.