How wood weight is calculated
Wood density is reported at a specific moisture content. The standard reference is specific gravity — the ratio of wood density to water density at a given moisture content. Multiply specific gravity by 62.4 lb/ft³ (the density of water) to get pounds per cubic foot at that MC.
The formula for weight at any MC:
Weight (lb) = SG × 62.4 × Volume (ft³) × (1 + MC/100 × shrinkage factor)
For simplicity, this calculator uses pre-computed densities at common MCs (kiln-dried 8%, air-dried 15%, green). For unusual MCs, the linear interpolation between dried and green density is accurate to within 5%.
Why moisture content matters so much
Green oak weighs about 4,700 lb per thousand board feet. Kiln-dried oak weighs about 3,400 lb per MBF. Same wood, different water weight — and water is heavy.
Implication: if you're hauling lumber from the yard in the back of a pickup, ask whether it's kiln-dried or green. A full-size pickup is rated for about 1,000-1,500 lb of payload. Green oak hits that limit with 6-8 boards. Kiln-dried oak can run 10-15 boards before you hit the same weight.
Common weights per board foot (kiln-dried, 8% MC)
- Lightest: Cedar, pine, paulownia — 1.5-2 lb/BF
- Medium: Walnut, cherry, mahogany — 2.5-3.5 lb/BF
- Heavy: Oak, ash, hard maple — 3.5-4.5 lb/BF
- Very heavy: Ipe, ebony, lignum vitae — 5-8 lb/BF
What "floats in water" means
Wood with specific gravity less than 1.0 floats; more than 1.0 sinks. Almost all common woods float when dry, because their cell walls (mostly cellulose) are less dense than water. A few exceptions: lignum vitae, ebony, and a handful of tropical hardwoods can sink even when dry.
This is mostly a curiosity for woodworkers, but it matters for: river-recovered logs (they sink, then are dragged up), boat-building (you want buoyant woods), and shipping (heavier woods cost more per BF to ship).
Frequently asked questions
How much does a typical workbench weigh?
A solid maple workbench (5'×2.5', 4" thick top) weighs 400-500 lb. A laminated MDF/plywood top weighs 150-200 lb. Add the base (legs, stretchers, vises) and you're looking at 500-700 lb total for a serious bench.
What's the weight of a full sheet of plywood?
3/4" birch plywood: ~75 lb. 1/2" MDF: ~50 lb. 1/4" lauan: ~20 lb. These vary by core material (MDF core is heavier than veneer core).
How much weight can a wood floor hold?
Most residential wood floors are designed for 40 lb/sq ft live load (per IRC). That's a bookshelf full of books, a pool table, or a piano. Heavier items (grand piano, large aquarium) require floor-joist reinforcement — consult a structural engineer.