How this calculator works
Lumber weight is volume times density. Volume uses the actual dressed dimensions, not the trade name: a nominal 2 by 4 is about 38 by 89 mm once surfaced. The density figures are indicative values at about 12% moisture content, the usual dry service condition for framing. Wet or freshly treated lumber is heavier, and a denser species in the same size can add a third or more to the load, which matters for trailers, shelves and roof framing.
Formula
Volume per board = actual length x actual width x actual thickness; total mass = volume per board x quantity x density. A nominal 2 x 4 is entered as 38 x 89 mm, not 50 x 100 mm.
Worked example
Ten 2.4 m boards measuring 38 by 89 mm contain 0.0812 m3. At 430 kg/m3 for SPF they weigh about 34.9 kg in total, or 3.49 kg each. The same boards in white oak at 770 kg/m3 weigh 62.5 kg.
Advertisement
Frequently asked questions
Why is the weight different from the label on the bundle?
Bundle weights are usually for a whole bunk at a stated moisture content, and they include packaging and dunnage. This figure is the wood alone at the density you chose.
Does pressure treatment add weight?
Yes. Treatment adds water and preservative, and freshly treated lumber can be much heavier than the dry density shown. Let treated boards dry before using these figures for a permanent load.
Can I use nominal dimensions?
No. Enter actual dressed sizes, because the nominal name overstates both thickness and width. The table below converts common nominal sizes to their surfaced dimensions.