Timber Volume and Weight Calculator
Volume, board area and weight for timber by species density.
Quick answer
With the default inputs: Length 4 · Width 200 · Thickness 50 etc.Total volume 0.8000 m³
Edit the inputs below to recalculate.Inputs
Result
Total volume
0.8000m³
| Volume per piece | 0.04000m³ |
| Mass per piece | 20.00kg |
| Total mass | 400.0kg |
| Equivalent board area | 16.00m² |
| Pieces per m³ | 25.0bars |
| Total length | 80.0m |
| Surface area per piece | 2.000m² |
| Board feet (reference) | 17.0bf |
Volume is net finished size; add 5-10 mm for sawing and planing when ordering. Air-dry density is at 12-15% moisture, and green timber is 20-40% heavier. Timber is priced by volume, not weight — weight matters only for haulage and lifting.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Volume per piece | V = length × width × thickness in metres |
| Total volume | V × quantity |
| Mass | V × air-dry density |
| Board area | total volume ÷ thickness |
| Pieces per m³ | N = 1 ÷ volume per piece |
| Board feet | 1 m³ ≈ 423.8 bf |
Twenty pieces at 40 × 200 × 50 mm and 500 kg/m³: 0.0400 m³ and 20.00 kg each — 0.8000 m³ and 400.0 kg in total, equivalent to 16.00 m² of 50 mm board.
How to work it out
- Convert to metres and compute the volume per piece: length × width × thickness. A 200 × 50 mm, 4 m length is 0.04 m³.
- Multiply by the count for total volume, then by air-dry density for weight. Density depends on moisture, and air-dry (12-15%) is the usual basis for pricing and haulage.
- Typical air-dry densities: pine and larch 450-550 kg/m³, fir 350-420, ash 600-700, oak 700-800, plywood 550-650.
- Boards are measured by area × thickness; decorative sheets are counted by the sheet at 1220 × 2440 mm.
- Round logs come from the volume tables, never from the cylinder formula, because the tables already account for taper and bark.
Where it goes wrong
- Using green density — freshly felled timber at 60-100% moisture reaches 900 kg/m³, overstating haulage and lifting by more than 60%.
- Applying the cylinder formula to logs — GB/T 4814 works from small-end diameter and taper rules, and a plain cylinder is out by 10-20%.
- Not allowing for bark — log diameters are quoted under bark and volumes use the debarked figure.
- Using nominal sizes for sawn timber — a specified 200 × 50 may plane to 190 × 45, so nominal overstates volume by about 10%.
Material and cost
Larch logs 1200-1800 CNY/m³, Scots pine 1500-2200, imported structural spruce 2000-3000, 18 mm plywood 60-120 per sheet, construction battens 1600-2400 CNY/m³.
On site
- Timber is anisotropic: strength along the grain is 10-20 times across it, so formwork battens must bear along the grain or they crush.
- Moisture matters: structural timber below 15%, joinery at 8-12%; wetter timber splits and distorts.
- Fire treatment adds 5-10% to weight, and density should be taken after treatment.
Basis
- GB/T 4814-2013 Volume tables for round logs
- GB 50005-2017 Standard for design of timber structures
- GB/T 1931-2009 Method for determination of moisture content in wood
FAQ
Why is timber sold by volume, not weight?
Because value follows usable volume and yield, not mass. The same volume of pine and hardwood differs twofold in weight yet yields identical members. Selling by weight rewards wet timber — 20-40% heavier but no more product — which is exactly why timber is settled by volume.
How do sawn timber and plywood convert?
By volume: 1 m³ is 20 m² at 50 mm, 33.3 m² at 30 mm and 55.6 m² at 18 mm. But sawn timber is solid and plywood is laminated, so they are far from interchangeable. In formwork the sawn member is the bending-resistant bearer while plywood is the wearing face — quantity them separately.
Does moisture content affect volume much?
Volume little, weight a lot. Drying from green to air-dry shrinks volume 3-8% but cuts mass 20-40%. That is why timber machined straight after delivery comes out undersized, and why timber codes require 15-20% moisture before installation — otherwise it cracks and distorts afterwards.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Timber Volume and Weight Calculator. 2026-10-25. https://jianzhujisuan.com/en/timber-volume
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.