Lumber Calculator

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.

Sixteen feet of wall at 16 inch centres, 8 foot studs in 2x4: 13 pieces, 104 linear feet, 69.3 board feet, 53.7 kg.

Thirteen, not twelve. Sixteen feet at 16 inch centres is twelve gaps, and both ends carry a stud. The same rule that gives 10 studs on a 12 foot wall gives 13 here, and it is the one place a framing count goes wrong by exactly one every time.

This count is the studs alone. Plates, noggins, cripples and the extra studs around openings are on top, and the simplest way to add them is to switch to Piece count and enter your own total once you have worked the wall out.

A 12 foot span at 16 inch centres in 10 foot 2x8: 10 pieces, 133.3 board feet, 106.9 kg.

Same 10 pieces as the 2x4 example, and twice the board feet — because board feet bill on the nominal section, and a 2x8 is twice the 2x4. The weight more than doubles too, and that figure uses the actual dressed 1.5 by 7.25 inches rather than the nominal 2 by 8.

A hundred kilos is the number worth reading before you book a van. Ten 2x8s at ten feet is a two-person lift and a roof rack you will regret.

Twenty 12 foot 2x6 in oak, entered directly through Piece count: 240 board feet, 73.2 metres of timber, and 292 kg.

Not everything is framed to centres. Blocking, noggins, fence rails, shelving and general stock are jobs where you know the number and want the rest — the board feet you will be billed for and the weight you have to move.

Species only moves the weight. The same twenty pieces in pine come to well under half that; oak is the reason this load needs a trailer rather than a roof rack, and it changes not a single board foot on the invoice.

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.