How to use it
Estimating a weight
Choose the species
From 28 North American woods in the Wood Handbook's tables. Each name is pinned to one botanical species: 'red oak' is northern red oak, hard maple is sugar maple.
Enter the moisture content
Kiln-dried furniture stock is usually close to the 6–10% the Handbook recommends for interior work; air-dried lumber outdoors is wetter; green, freshly sawn wood can hold from about 30% to more than 200%.
Enter the size
Thickness and width in inches with length in feet, or millimetres and metres — the switch converts what you have typed. Use the actual size of the boards at that moisture, not the nominal size.
Enter how many boards
The weight is for all of them together.
The method
Weight from specific gravity
Sx = S0 × (1 − x ÷ FSP)
Gx = G12 × (100 − S12) ÷ (100 − Sx), for x below FSP; Gx = Gb at or above it
ρx = 1,000 kg/m³ × Gx × (1 + x ÷ 100)
weight = volume × ρx
- x
- moisture content (%)
- S0, Sx
- volumetric shrinkage from green to ovendry, and to x (%)
- FSP
- fiber saturation point: 30%, or 22% for western redcedar and redwood (%)
- Gb, G12, Gx
- specific gravity green, at 12% and at x, all on ovendry mass
- ρx
- density including the water (kg/m³)
Wood Handbook Eqs. 4–9, 4–10 and 4–14. Results are converted with exact constants: 25.4 mm per inch, 0.3048 m per foot, 0.45359237 kg per pound.
| Boards | Moisture | Density | Weight |
|---|---|---|---|
| Black walnut, 1 × 6 in × 8 ft | 12% | 616 kg/m³ (38.5 lb/ft³) | 5.81 kg (12.8 lb) |
| White oak, two at 20 × 150 mm × 2 m | 12% | 762 kg/m³ | 9.14 kg (20.1 lb) |
| Northern red oak, any size | 8% | 694 kg/m³ (43.3 lb/ft³) | — |
| White oak, green | 60% | 960 kg/m³ (59.9 lb/ft³) | — |
Worked by hand from the formulas above and among the calculator's test cases. At 12%, density is simply 1,000 × G12 × 1.12.
Why one number cannot fit every board
- Moisture. Water adds weight directly, and below fiber saturation the wood also shrinks, so density rises faster than the water alone suggests. Above about 30% the volume stops changing and only the free water adds weight.
- The species average. The Handbook puts the coefficient of variation of ovendry density within common domestic species at about 10%; within a species it varies with the share of earlywood and latewood and of heartwood and sapwood, and in some species with minerals and extractives.
- Green weight. Fresh-sawn wood's moisture differs between heartwood and sapwood and within a single board; enter a measured moisture content if you have one.
- Specific gravity bases. A specific gravity always uses ovendry mass, but the volume it divides by may be green, at 12% or at another moisture content. Mixing bases is the commonest error in weight charts.
What it does not cover
- Plywood and panels. Their density depends on species mix, adhesive and construction; no panel data is used here.
- Treated lumber. Preservative and the water it is applied in add weight that the species data does not include.
- Standing trees and logs. The weight of a tree needs its volume and green moisture, which this board calculator does not estimate; board feet in a log are on the log board foot calculator.
- Species not listed. This version covers 28 domestic species only; imported woods are not included.
Before relying on a weight estimate
- Species matched to the botanical name listed
- Moisture content measured, not assumed
- Actual sizes entered, not nominal
- About 10% allowed either way for board-to-board variation
- Panels, treated lumber and logs weighed some other way
- A real scale used where the weight matters for safety
How moisture content moves a board's size is on the wood movement calculator; grades and sizes in the lumber guide; and the whole buying decision in choosing lumber.
Sources
Specific gravities are the Handbook's averages for small clear specimens; real boards with knots, sapwood, reaction wood or resin may differ. The calculator anchors below fiber saturation on the tabulated 12% value and above it on the green value; because those two come from separate tests, the result steps by a few percent at the fiber saturation point.
- 1.
Chapter 5: Mechanical Properties of Wood. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Specific gravity of the 28 species, green (basic, on green volume) and at 12% moisture content (on volume at 12%), Table 5–3a.
- 2.
Chapter 4: Moisture Relations and Physical Properties of Wood. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Specific gravity defined on ovendry mass and the volume at a stated moisture content (Table 4–5); water at 4 °C as 1,000 kg/m³ (62.43 lb/ft³); converting specific gravity between moisture contents (Eq. 4–10) with volumetric shrinkage from green (Eq. 4–9, Table 4–3), or 26.5 × Gb where shrinkage is unknown (Eq. 4–12); density including water ρx = ρw·Gx·(1 + x/100) (Eq. 4–14); the white ash worked example (Gb 0.55, G12 about 0.605, about 678 kg/m³ at 12%); no volume change above fiber saturation; green moisture content from about 30% to over 200%; a coefficient of variation of about 10% for ovendry density within common domestic species.
- 3.
Chapter 2: Characteristics and Availability of Commercially Important Woods. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Botanical names for the common names used.
About this calculator
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