PreConstruct AIA Canadian drawing set can name the same stud three ways: 2x4, 38 × 89, or “2x4 S-P-F” on a wall type. They are one piece of wood. The nominal size (2x4) is its name; the dressed size (1-1/2 × 3-1/2 in, or 38 × 89 mm) is what it measures once it has been dried and planed.
Lumber sizes in millimetres
Dressed dry sizes, thickness by width. The millimetres are the inches × 25.4, rounded to the millimetre, which is how Canadian codes and drawings write them.
| Nominal | Actual (in) | Actual (mm) | Width (mm, exact) |
|---|---|---|---|
| 2x2 | 1-1/2 × 1-1/2 | 38 × 38 | 38.10 |
| 2x3 | 1-1/2 × 2-1/2 | 38 × 64 | 63.50 |
| 2x4 | 1-1/2 × 3-1/2 | 38 × 89 | 88.90 |
| 2x6 | 1-1/2 × 5-1/2 | 38 × 140 | 139.70 |
| 2x8 | 1-1/2 × 7-1/4 | 38 × 184 | 184.15 |
| 2x10 | 1-1/2 × 9-1/4 | 38 × 235 | 234.95 |
| 2x12 | 1-1/2 × 11-1/4 | 38 × 286 | 285.75 |
| 4x4 | 3-1/2 × 3-1/2 | 89 × 89 | 88.90 |
The 2x sizes are all 38 mm thick, so wall plates of 2x lumber meet the BC Building Code 2018's “not less than 38 mm thick” (Section 9.23.11; check the edition your project is built under). Lumber surfaced green is a little larger than these sizes and shrinks as it dries.
Quick answers
What size is a 2x4 in mm?
38 × 89 mm: 1-1/2 in is 38.1 mm and 3-1/2 in is 88.9 mm.
What size is a 2x6 in mm?
38 × 140 mm: 5-1/2 in wide is 139.7 mm.
What is a 38 × 89 in inches?
A 2x4: 1-1/2 × 3-1/2 in.
What size is a 2x10 and a 2x12 in mm?
38 × 235 mm and 38 × 286 mm: 9-1/4 and 11-1/4 in wide.
What size is a 4x4 in mm?
89 × 89 mm: 3-1/2 × 3-1/2 in.
How many board feet in a 2x4x8?
5.33 board feet: 2 × 4 × 8 ÷ 12. Board feet are counted on the nominal size, not the dressed one, so a 2x6x12 is 12 and a 2x10x16 is 26.67.
Metric stud spacing
A metric set writes spacing as 400 or 600 mm on centre; an imperial one as 16 or 24 in, which are 406.4 and 609.6 mm. Count studs at the spacing the drawings print. A 6 m wall at 400 mm is 6000 ÷ 400 = 15, plus one to close the run: 16 studs before openings and corners. The wood wall framing calculator does the rest of the wall: extras at openings and corners, plates and sheathing.
Lengths are still sold in feet
Even on a metric job, studs and plates are bought by the foot. An 8 ft piece is 2.438 m, a 10 ft 3.048 m, a 12 ft 3.658 m, a 16 ft 4.877 m. Turn the metres you measure into pieces at the lengths your yard stocks.
What this guide does not tell you
Which size a stud, joist, rafter, header or beam has to be. Those come from the drawings, the span tables of the code your project is built under, and the engineer, and engineered lumber from its supplier. This guide is for reading the size off the drawings and buying it.