Timber calculator
Work out the cubic metres, linear metres and cost of a timber order, with the finished size of 47 mm C16 carcassing timber.
Pick a stock section or type your own. For 47 mm timber, use the size it is sold as.
For 4800 mm, type 4.8.
Timber volume
- Volume
- 0.226 m³0.0226 m³ per piece
- Total length
- 48 m
- Finished size
- 45 × 95 mm0.205 m³ of wood at the finished size
Cost
From the price label or the merchant’s quote. Leave empty to skip the cost.
- Total cost
- –
- Per piece
- –
- Per cubic metre
- –
Estimate only. Check the product label and the building regulations where you live before you buy or build.
Quick answer
Multiply the thickness by the width and the length, all in metres, then by the number of pieces. Ten pieces of 47 × 100 mm timber, 4.8 m long, are 0.047 × 0.1 × 4.8 × 10 = 0.2256 m³ (0.226 m³ rounded) and 48 linear metres. At their finished size of 45 × 95 mm the same ten pieces hold 0.205 m³ of wood.
How to use the timber calculator
- Pick a size such as 47 × 100 mm or 38 × 89 mm CLS, or type the thickness and width in millimetres. For 47 mm C16 timber, use the size it is sold as; the finished size appears with the result.
- Enter the length of each piece in metres and the number of pieces. For 4800 mm, type 4.8.
- Read the volume in cubic metres, the volume per piece and the total length in linear metres. For 47 mm sizes you also get the finished size and the volume of wood at that size.
- To check a price, choose whether it is quoted per metre, per piece or per cubic metre, and type it. The total cost and the other two prices appear below. Switch to Imperial to enter sizes in inches and lengths in feet.
How do you work out the volume of timber?
Multiply thickness by width by length, with all three in metres, then multiply by the number of pieces. Divide millimetres by 1000 to get metres, so a 47 × 100 mm section is 0.047 × 0.1 m and one 4.8 m piece is 0.047 × 0.1 × 4.8 = 0.02256 m³.
The total length in linear metres is the length of one piece times the count. A price per piece divided by the volume of one piece gives the price per cubic metre, and divided by its length gives the price per metre. That lets you compare a merchant that prices by the metre with one that prices by the cubic metre.
volume per piece (m³) = thickness (m) × width (m) × length (m)total volume (m³) = volume per piece × number of piecestotal length (m) = length of one piece × number of piecesprice per m³ = price per piece ÷ volume per pieceprice per metre = price per piece ÷ length of one pieceCLS and C16 timber sizes: nominal, finished and volume per 4.8 m
Nominal and finished sizes of machined, kiln dried C16 carcassing timber as BSW Timber lists them. Volumes are worked out for one 4.8 m piece, once on the nominal size and once on the finished size.
| Size (mm) | m³ per 4.8 m, nominal | m³ per 4.8 m, finished |
|---|---|---|
| CLS 50 × 75, finished 38 × 63 | 0.0180 | 0.0115 |
| CLS 50 × 100, finished 38 × 89 | 0.0240 | 0.0162 |
| CLS 50 × 150, finished 38 × 140 | 0.0360 | 0.0255 |
| 47 × 75, finished 45 × 70 | 0.0169 | 0.0151 |
| C16 47 × 100, finished 45 × 95 | 0.0226 | 0.0205 |
| C16 47 × 125, finished 45 × 120 | 0.0282 | 0.0259 |
| C16 47 × 150, finished 45 × 145 | 0.0338 | 0.0313 |
| C16 47 × 175, finished 45 × 170 | 0.0395 | 0.0367 |
| C16 47 × 200, finished 45 × 195 | 0.0451 | 0.0421 |
| C16 47 × 225, finished 45 × 220 | 0.0508 | 0.0475 |
BSW lists CLS in 2.4, 3.0 and 4.8 m lengths (38 × 140 mm in 4.8 m only) and 47 mm timber in 2.4, 3.0, 3.6, 4.2 and 4.8 m; it marks 47 × 75 mm as not graded. In the calculator, CLS is listed by its finished size and 47 mm timber by its nominal size.
Worked examples
Ten pieces of 47 × 100 mm timber, 4.8 m long
Each piece is 0.047 × 0.1 × 4.8 = 0.0226 m³, so ten pieces are 0.226 m³ and 48 linear metres. That volume is counted on the nominal size the timber is sold as.
The timber is finished at 45 × 95 mm, so the ten pieces hold 0.205 m³ of wood, 9% less than the nominal figure. Ask which of the two sizes a price per cubic metre is based on before you compare quotes.
From a price per metre to a price per cubic metre for 47 × 150 mm joists
An order of twelve 47 × 150 mm joists, 3.6 m long, is 0.047 × 0.15 × 3.6 = 0.0254 m³ a joist, 0.305 m³ in total and 43.2 linear metres.
Say the timber is £5.00 a metre. Each joist costs £18.00, the twelve cost £216.00, and the price per cubic metre on the nominal size is £709.22. Type the finished size, 45 × 145 mm, and the same £5.00 a metre works out at £766.28 per cubic metre.
Why is 47 × 100 mm timber only 45 × 95 mm?
47 × 100 mm is the nominal size the timber is sold under, and 45 × 95 mm is its finished size. BSW Timber lists its machined, kiln dried C16 timber this way: 47 × 75 mm is 45 × 70 mm finished, 47 × 150 mm is 45 × 145 mm and 47 × 225 mm is 45 × 220 mm. Its CLS is listed as nominal 50 × 75, 50 × 100 and 50 × 150 mm, finished 38 × 63, 38 × 89 and 38 × 140 mm.
The gap matters when a price is quoted per cubic metre. For 47 × 100 mm the finished size holds 9% less wood than the nominal size, and for CLS the gap is 29 to 36%. The calculator counts the size you type, so type the nominal size to check a quote made on the nominal size, and the finished size to see how much wood you get. Set out and cut to the finished size.
Questions
How many metres of timber are in a cubic metre?
One cubic metre of 47 × 100 mm timber is 212.8 linear metres: divide 1 by the section in metres, 1 ÷ (0.047 × 0.1). For 47 × 150 mm it is 141.8 m and for 47 × 200 mm it is 106.4 m. Counted on the finished size the figures are higher, 233.9 m for 45 × 95 mm, because each metre holds less wood.
How do I convert a price per metre to a price per cubic metre?
Divide the price per metre by the cubic metres in one metre of the section. One metre of 47 × 150 mm timber is 0.00705 m³, so £5.00 a metre is £5.00 ÷ 0.00705 = £709.22 per cubic metre. To go back, multiply the price per cubic metre by 0.00705. Ask whether a cubic metre price uses the nominal or the finished size.
What size is CLS timber?
CLS is 38 × 63, 38 × 89 or 38 × 140 mm finished, which BSW Timber lists as nominal 50 × 75, 50 × 100 and 50 × 150 mm. BSW describes it as kiln dried and C16 graded, and sells it in 2.4, 3.0 and 4.8 m lengths, with 38 × 140 mm in 4.8 m only. The calculator lists CLS by its finished size.
What lengths does timber come in?
BSW Timber lists 47 mm C16 timber in 2.4, 3.0, 3.6, 4.2 and 4.8 m lengths, steps of 0.6 m, and sawn battens such as 25 × 38 and 25 × 50 mm in 3.0, 3.6, 4.2 and 4.8 m. A 4.8 m length is 15 ft 9 in. Pick the length that cuts into your pieces with the least waste, then enter that length and the count.
What is a 2x4 in mm?
A US 2x4 is 1½ × 3½ in when dry, which is 38.1 × 88.9 mm, so it matches 38 × 89 mm CLS. ‘2x4’ is a nominal size from the American Softwood Lumber Standard (PS 20), and the real piece is smaller than its name. Among BSW’s C16 sizes, the nearest is 47 × 100 mm, finished 45 × 95 mm.
Sources
- BSW Timber, Machined Carcassing (checked 19 October 2026)CLS and C16 nominal and finished sizes, lengths, kiln dried C16 grading, 47 × 75 mm not graded.
- BSW Timber, General Construction (checked 19 October 2026)Sawn batten sizes (25 × 38 and 25 × 50 mm) and lengths.
- National Institute of Standards and Technology (published by the American Lumber Standard Committee), Voluntary Product Standard PS 20-25, American Softwood Lumber Standard (checked 19 October 2026)Table 3: a US nominal 2x4 is 1½ × 3½ in (38.1 × 88.9 mm) dry.
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