Lumber weight calculator
Lumber weight tables disagree with each other because they answer different questions: green or dry, nominal or actual, per piece or per board foot. This one states all three so the number can be checked.
Your boards
How this is calculated
Weight is actual volume times density, with a moisture correction. Nothing here uses the nominal size except the board-foot figure, which is a purchasing unit rather than a physical measurement.
- Volume = actual thickness × actual width × length in inches ÷ 1728, in cubic feet.
- Moisture factor = (1 + MC ÷ 100) ÷ 1.12. Densities in the table are quoted at 12%, so this rescales the water fraction.
- Weight = volume × density × moisture factor.
- Board feet = nominal thickness × nominal width × length ÷ 12 — the number the yard will invoice.
Worked example
Ten 2×8×12 in SPF at 12% moisture content:
- Actual = 1.5 × 7.25 × 144 in = 1,566 in³ = 0.906 ft³
- Weight each = 0.906 × 27 = 24.5 lb
- Ten pieces = 245 lb
- Board feet each = 2 × 8 × 12 ÷ 12 = 16 bf, so the invoice says 160 bf
Note the ratio: 16 board feet per piece but only 0.906 cubic feet, which is 7.25 board feet of actual wood. Roughly 55% of the nominal volume is air where the saw removed it.
Where the weight figure is used
- Trailer and vehicle loads. A 12 ft trailer at 3,500 lb capacity carries about 140 2×8×12s — but load it by axle rating, not by total.
- Lifting and carrying. Two people can carry a 24 ft 6×6 between them; a 20 ft ipe 2×10 is a machine job.
- Beam self-weight. When you check a beam against a span table, the dead load allowance usually already includes the member, so do not add it twice.
- Shipping and freight class. Hardwood sold by board foot is often freighted by weight, and ipe at 69 lb/ft³ is a different freight class from cedar at 23.
Where the weight figure breaks down
- It does not model the actual board. Density varies within a species by 10–15%, and a knot or a pitch pocket changes local weight. Treat the result as the centre of a range.
- It does not account for treatment chemicals. ACQ and copper azole add mass, roughly 3–8% depending on retention level. Wet treated stock is heavier than the moisture correction alone predicts.
- It does not size anything. A beam's capacity is not a function of its weight — see span tables.
- It does not convert to metric. Divide pounds by 2.205 if you need kilograms; that is the only conversion offered.
Questions people actually ask
How much does a 2x8x12 weigh?
In SPF at 12% moisture it is about 24.5 lb. In treated southern yellow pine at 25% it is closer to 41 lb — same board, wetter wood, denser species. That spread is why a single figure in a chart is only ever an average.
Why is my treated lumber so much heavier than the chart?
Two reasons. Treated stock ships at 25–30% moisture content, well above the 12% the density tables assume, and the preservative itself adds 3–8% mass. A wet 2×8×12 that weighs 40 lb is not a defect — it is water.
Does lumber lose weight as it dries?
Yes, and it keeps losing it for months. A treated 2×8 can shed 30% of its weight between the yard and equilibrium indoors. Deck boards, bought wet and installed within a week, settle somewhere in between.
Is board foot weight the same as actual weight?
No. Board feet use nominal dimensions, so a 2×8 contains 16 bf by the invoice but only about 7.25 bf of actual wood. If you need mass, use cubic feet; if you need to pay for it, use board feet.
Which deck species is heaviest?
Of the common ones, ipe and cumaru at roughly 68–69 lb/ft³, which is nearly three times western red cedar. It matters for handling, for trailer loads, and for the framing that carries it.