Wood weight calculator

Have a moisture meter reading, or weighing freshly sawn logs or slabs? Change How dry is the wood? and the calculator adjusts the density. New to this? Words explained.

How the weight is estimated

The calculator multiplies the board’s actual volume by a typical density for the species at about 12% moisture content — the range most kiln-dried and well air-dried lumber ends up at indoors. The species densities follow the specific gravities in the USDA Forest Products Laboratory’s Wood Handbook and the dried weights listed by The Wood Database.

weight = thickness × width × length × density
1 board foot = 0.00236 m³ = 1/12 cu ft
lb per board foot ≈ density (lb/cu ft) ÷ 12

Moisture: meter readings and green wood

Wood weight is mostly a question of water. Choose I have a moisture meter reading or Freshly sawn (green) and the calculator re-works the density with the method in chapter 4 of the USDA Wood Handbook: it backs out the wood’s basic specific gravity from the 12% density, allows for the wood swelling as it takes on water up to the fiber saturation point (taken as 30%), and adds the water’s weight. Above 30% the volume stops changing, so extra water just adds weight.

G12 = density at 12% ÷ 1,120 kg/m³
Gb = G12 ÷ (1 + 0.159 × G12)   (basic specific gravity)
G = Gb ÷ (1 − 0.265 × Gb × (1 − MC/30))   below 30% MC
density = 1,000 kg/m³ × G × (1 + MC/100)

A quicker rule you may see — multiply the 12% weight by (1 + MC/100) ÷ 1.12 — ignores that swelling, so it overstates the weight of wet wood: by about 4% for red oak at 20% moisture and about 10% near 30%. Green weights use the Handbook’s average green moisture content for the species (table 4-1), midway between its heartwood and sapwood figures; eastern white pine, SPF, spruce, Scots pine, mahogany and teak are not in that table, so for those enter a meter reading instead. A red oak 1 × 6 in × 8 ft board that weighs about 14.6 lb dry comes to about 15 lb at 20% moisture and about 20.6 lb green.

Example: a dry red oak board 1 × 6 in × 8 ft is 0.333 cu ft. At about 44 lb/cu ft, it weighs roughly 14.6 lb. More worked examples: How much does a 2x4x8 weigh, How much does a board foot of oak weigh and, in metric, Weight of 45 × 95 mm × 2.4 m timber.

Typical densities at about 12% moisture

Plywood, OSB and MDF sheets

Choose Sheet at the top to weigh sheet goods. The calculator uses a full 4 × 8 ft sheet (1220 × 2440 mm in metric) and a typical density for each panel type. Softwood plywood and OSB are set to match the approximate panel weights that APA – The Engineered Wood Association gives in its Panel Design Specification for dead-load calculations: about 2.3 lb per square foot for 3/4 in plywood, with OSB roughly 10% heavier. MDF and birch plywood vary more from brand to brand, so treat those figures as mid-range and check the label.

Watch the thickness. Structural plywood and OSB sold as “3/4”, “5/8” or “1/2” are usually 23/32, 19/32 or 15/32 in thick — the grade stamp prints the real figure, and the thickness list above includes both. The most common sheet is worked through on How much does a sheet of 3/4 plywood weigh. To weigh a whole floor or wall, count the sheets first — for example How many sheets of plywood for a 12x12 subfloor — and enter that number above.

Why your board may weigh more

• Moisture. Every percentage point of moisture adds weight. Lumber straight from a big-box store rack is often above 12%, and green wood of some species can be twice as heavy; enter a meter reading to see the difference.
• Nominal vs actual. Enter the measured size. A 2×4 is 1½ × 3½ in; entering 2 × 4 overstates its weight by about half. Pick a nominal size from the list and the calculator uses the actual size for you.
• Treatment and glue. Pressure-treated lumber is often shipped wet from treatment, and panel products carry glue and resin. For those, the manufacturer’s data sheet beats a species average.