Timber size converter
What 4 × 2 is in millimetres, why sawn 100 × 50 comes out at 94 × 44, what CLS measures, and a calculator for pieces, linear metres, cubic metres and price.
Convert a section
Imperial names to metric sizes
Three sizes exist for the same piece of wood. The nominal size is the rough-sawn size the name comes from. Regularised carcassing has been machined to a consistent thickness, usually 47 mm instead of 50. PAR (planed all round) loses about 3 mm on every face. All three are sold as "4 × 2".
| Trade name | Nominal sawn | Regularised (sold as) | PAR finished (approx.) | Typical use |
|---|---|---|---|---|
| 1" × 1" | 25 × 25 mm | 25 × 25 mm | 20 × 20 mm | Batten, beading |
| 2" × 1" | 50 × 25 mm | 50 × 25 mm | 44 × 20 mm | Roofing batten, trim |
| 3" × 1" | 75 × 25 mm | 75 × 25 mm | 69 × 20 mm | Skirting, fascia |
| 4" × 1" | 100 × 25 mm | 100 × 25 mm | 94 × 20 mm | Skirting, shelving |
| 6" × 1" | 150 × 25 mm | 150 × 25 mm | 144 × 20 mm | Fascia, wide boards |
| 2" × 2" | 50 × 50 mm | 47 × 50 mm | 44 × 44 mm | Framing, posts |
| 3" × 2" | 75 × 50 mm | 47 × 75 mm | 69 × 44 mm | Studwork, joists |
| 4" × 2" | 100 × 50 mm | 47 × 100 mm | 94 × 44 mm | Studwork, joists |
| 5" × 2" | 125 × 50 mm | 47 × 125 mm | 119 × 44 mm | Joists |
| 6" × 2" | 150 × 50 mm | 47 × 150 mm | 144 × 44 mm | Joists, rafters |
| 7" × 2" | 175 × 50 mm | 47 × 175 mm | 169 × 44 mm | Joists |
| 8" × 2" | 200 × 50 mm | 47 × 200 mm | 194 × 44 mm | Joists |
| 9" × 2" | 225 × 50 mm | 47 × 225 mm | 219 × 44 mm | Floor joists |
| 3" × 3" | 75 × 75 mm | 75 × 75 mm | 69 × 69 mm | Posts |
| 4" × 4" | 100 × 100 mm | 100 × 100 mm | 94 × 94 mm | Posts |
| 6" × 3" | 150 × 75 mm | 75 × 150 mm | 144 × 69 mm | Beams, lintels |
PAR finished sizes vary by mill by a millimetre or two. Where it matters, such as matching existing joists, measure a piece from the pack.
CLS timber sizes
CLS is already finished, with eased corners, and is sold at its true size. It is smaller than the sawn equivalent: CLS 2 × 4 is 38 × 89 mm, not 47 × 100.
| Name | Finished size |
|---|---|
| CLS 2 × 3 | 38 × 63 mm |
| CLS 2 × 4 | 38 × 89 mm |
| CLS 2 × 6 | 38 × 140 mm |
| CLS 2 × 8 | 38 × 184 mm |
| CLS 2 × 10 | 38 × 235 mm |
Sawn to PAR finished sizes
Per dimension. Planing takes roughly 3 mm off each face on small sections and a little more on large ones.
| Sawn (nominal) mm | PAR finished mm |
|---|---|
| 25 | 20 |
| 32 | 27 |
| 38 | 32 |
| 47 | 44 |
| 50 | 44 |
| 63 | 57 |
| 75 | 69 |
| 100 | 94 |
| 125 | 119 |
| 150 | 144 |
| 175 | 169 |
| 200 | 194 |
| 225 | 219 |
Standard lengths
| Metres | Feet |
|---|---|
| 1.8 m | 5.9 ft |
| 2.1 m | 6.9 ft |
| 2.4 m | 7.9 ft |
| 2.7 m | 8.9 ft |
| 3.0 m | 9.8 ft |
| 3.3 m | 10.8 ft |
| 3.6 m | 11.8 ft |
| 3.9 m | 12.8 ft |
| 4.2 m | 13.8 ft |
| 4.5 m | 14.8 ft |
| 4.8 m | 15.7 ft |
| 5.1 m | 16.7 ft |
| 5.4 m | 17.7 ft |
| 6.0 m | 19.7 ft |
Pieces, linear metres, cubic metres and price
Run a trade counter? Stop re-typing delivery notes.
TradeSorter reads a supplier invoice into a purchase order and books the stock in. 30-day free trial, no card.
Common questions
4 × 2 is 100 × 50 mm nominal sawn. Regularised carcassing is sold as 47 × 100 mm, and planed (PAR) 4 × 2 finishes at about 94 × 44 mm. CLS 2 × 4 is a different, smaller section: 38 × 89 mm.
Sawn sizes are nominal. Planing (PAR, planed all round) takes roughly 3 mm off each face, so 100 × 50 sawn finishes at about 94 × 44, and regularising takes carcassing from 50 to 47 mm on the thin side.
CLS (Canadian Lumber Standard) is sold at its finished size with rounded corners: 38 × 63 (2 × 3), 38 × 89 (2 × 4) and 38 × 140 (2 × 6) are the common sections, in C16 or C24 grades.
Width (m) × thickness (m) × length (m) × number of pieces. Ten lengths of 47 × 100 mm at 4.8 m is 0.047 × 0.1 × 4.8 × 10 = 0.226 m³. The calculator on this page does it, and converts a per-m³ price to per piece.
Softwood is stocked in 0.3 m steps: 1.8, 2.1, 2.4, 2.7, 3.0, 3.6, 4.2, 4.8, 5.4 and 6.0 m are the most common. 2.4 m and 4.8 m roughly match the old 8 ft and 16 ft.