Board feet, piece count and weight for framing, decking and finish work.
A "2x4" really measures 1½ by 3½ inches. Board feet bill on the nominal size; weight uses the actual one.
Measured stud centre to stud centre.
Extra to order for cuts and warped boards. 10% is typical.
Nothing to work out yet
Enter values for Length (per piece), Span to Cover, Spacing (centres).
Give it the span and the centres you are framing to and it counts the pieces: both ends carry one, so a 12 ft wall at 16 inch centres takes 10 studs, not 9. Board feet then use the nominal size, because that is how timber is sold and billed — nominal width × nominal height × total linear feet, divided by 12. Weight uses the actual dressed size instead, since a "2x4" really measures 1½ by 3½ inches and pricing the load off the nominal figure would overstate it by about a third. Waste is applied to the piece count and rounded up to whole boards. Total linear length is the pieces multiplied by their length — the figure a merchant cuts from and a delivery is measured in, which board feet alone does not tell you. If you already know the count, switch the first dropdown and enter it directly.
A 12 foot span at 16 inch centres, 2x4 pine, 8 foot pieces. The calculator returns 10 pieces, 80 linear feet, 53.3 board feet and 41.3 kg.
Ten, not nine. A 12 foot wall at 16 inch centres has nine gaps, and both ends carry a piece — so it is gaps plus one. That fencepost rule is the single most common framing miscount, and it is why the drawing beside the form shows five boards with four gaps rather than telling you the answer in words.
Board feet then use the NOMINAL size: 2 × 4 × 80 linear feet ÷ 12 = 53.3 BF. Weight uses the ACTUAL dressed size instead, 1.5 by 3.5 inches, which is why 53.3 board feet of pine comes to 41 kg rather than the 60-odd the nominal figure would suggest.
Assuming a 2x4 measures 2 by 4 inches. It does not — it finishes at 1.5 by 3.5 after planing, and every nominal size is smaller than its name in the same way. The drawing on this page shows the sold size as a dashed outline around the real timber for exactly that reason.
Where it costs money is the direction of the error. Timber is BILLED on the nominal size, so board feet must use it. But weight, and anything you are sizing a load or a trailer around, must use the actual. Price the load off the nominal figure and you overstate it by about a third.
Pieces, the nominal size, the length, and the species. Board feet is the pricing unit, and it is on the results for that reason, but a merchant cuts and delivers pieces of a stated length — which is what Total Linear Length is there to tell you.
Species changes weight, not board feet. Pine, fir, cedar and oak of the same size are billed identically and load very differently, so the species dropdown moves the weight row and nothing else. If you are hiring a van rather than a lorry, that is the row to read.
The working shows the piece count, the linear feet, the nominal figures the board feet came from, and states plainly that the weight used the actual section. Four lines, and each one is checkable against a tape.
If you already know your count — buying stock for blocking, noggins or a fence rather than framing to centres — switch the first dropdown to Piece count and enter it directly. The board feet and the weight are worth having either way, and there is no sensible way to reverse-engineer a span and a spacing that happen to produce twenty.