Lumber dimensions chart
Nominal sizes name the rough-sawn board; the dressed (planed) size is what you measure. The American Softwood Lumber Standard, PS 20, sets the minimum dressed sizes for dry lumber (19% moisture or less)[1]:
| Nominal | Actual (in) | Actual (mm) | Lb per ft (dry Douglas-fir) | Floor joist span* |
|---|---|---|---|---|
| 2x4 | 1-1/2″ × 3-1/2″ | 38.1 × 88.9 | 1.22 | — |
| 2x6 | 1-1/2″ × 5-1/2″ | 38.1 × 139.7 | 1.92 | — |
| 2x8 | 1-1/2″ × 7-1/4″ | 38.1 × 184.1 | 2.53 | 12 ft 9 in |
| 2x10 | 1-1/2″ × 9-1/4″ | 38.1 × 234.9 | 3.23 | 15 ft 7 in |
| 2x12 | 1-1/2″ × 11-1/4″ | 38.1 × 285.8 | 3.93 | 18 ft 1 in |
* No. 2 Douglas fir-larch at 16 in centres, 40 psf live and 10 psf dead load, computed with the method behind the IRC floor joist tables; see the joist span calculator. Weights use the USDA Wood Handbook density at 12% moisture[5].
2x4 dimensions
A 2x4 measures 1-1/2″ × 3-1/2″ dry (38.1 × 88.9 mm) under PS 20[1]. It is the standard stud: under the IRC, 2x4 bearing studs may be 24 in apart when they carry only a roof, and 16 in when they also carry a floor[6].
| Property | Value |
|---|---|
| Actual size (dry) | 1-1/2″ × 3-1/2″ |
| Metric | 38.1 × 88.9 mm |
| Board feet per 8 / 12 / 16 ft | 5.33 / 8 / 10.67 |
| Weight per foot, dry Douglas-fir | 1.22 lb |
| Weight per foot, dry lodgepole pine (SPF) | 1.05 lb |
2x6 dimensions
A 2x6 measures 1-1/2″ × 5-1/2″ dry (38.1 × 139.7 mm) under PS 20[1]. It is the stud for thicker, better-insulated exterior walls (24 in apart for one floor and a roof under the IRC[6]), and common deck boards and stair treads.
| Property | Value |
|---|---|
| Actual size (dry) | 1-1/2″ × 5-1/2″ |
| Metric | 38.1 × 139.7 mm |
| Board feet per 8 / 12 / 16 ft | 8 / 12 / 16 |
| Weight per foot, dry Douglas-fir | 1.92 lb |
| Weight per foot, dry lodgepole pine (SPF) | 1.64 lb |
2x10 dimensions
A 2x10 measures 1-1/2″ × 9-1/4″ dry (38.1 × 234.9 mm) under PS 20[1]. As a floor joist it spans about 15 ft 7 in at 16 in centres in No. 2 Douglas fir-larch (40/10 psf), and it is a common header and deck joist size[7].
| Property | Value |
|---|---|
| Actual size (dry) | 1-1/2″ × 9-1/4″ |
| Metric | 38.1 × 234.9 mm |
| Board feet per 8 / 12 / 16 ft | 13.33 / 20 / 26.67 |
| Weight per foot, dry Douglas-fir | 3.23 lb |
| Weight per foot, dry lodgepole pine (SPF) | 2.76 lb |
2x12 dimensions
A 2x12 measures 1-1/2″ × 11-1/4″ dry (38.1 × 285.8 mm) under PS 20[1]. It is the minimum size for deck stair stringers in AWC's DCA 6[8] and spans about 18 ft 1 in as a No. 2 Douglas fir-larch floor joist at 16 in centres.
| Property | Value |
|---|---|
| Actual size (dry) | 1-1/2″ × 11-1/4″ |
| Metric | 38.1 × 285.8 mm |
| Board feet per 8 / 12 / 16 ft | 16 / 24 / 32 |
| Weight per foot, dry Douglas-fir | 3.93 lb |
| Weight per foot, dry lodgepole pine (SPF) | 3.36 lb |
Metric and other countries
Canada uses the same dressed sizes, written as 38 × 89 mm for a 2x4 and 38 × 140, 184, 235 and 286 mm for the wider sizes[2]. UK CLS studs are 38 × 63 and 38 × 89 mm, and sawn sizes such as 47 × 100 and 47 × 150 mm are common[3]; Australian MGP10 framing comes in 70 × 35, 90 × 35 and 90 × 45 mm[4].
Common lumber size mistakes
- Planning with nominal sizes. A wall of 2x4s is 3-1/2 in thick before sheathing and drywall.
- Mixing dry and green. Green lumber is cut larger (a green 2x4 is 1-9/16 × 3-9/16 in) and shrinks as it dries[1].
- Board feet from actual sizes. Softwood is tallied on nominal size; use the board foot calculator. For a whole list with prices, use the lumber calculator.
Frequently asked questions
What are the actual dimensions of a 2x6?
1-1/2 × 5-1/2 in (38.1 × 139.7 mm) dry.
What size is a 2x10 really?
1-1/2 × 9-1/4 in (38.1 × 235 mm) dry; a 2x12 is 1-1/2 × 11-1/4 in.
Why is a 2x4 not 2 by 4 inches?
The name is the rough-sawn size. Drying and planing reduce it to the dressed size set by PS 20: 1-1/2 × 3-1/2 in.
How much does a 2x10 weigh per foot?
About 3.2 lb per foot in dry Douglas-fir and 2.8 lb in dry lodgepole pine (SPF).
Sources
- Voluntary Product Standard PS 20-25, American Softwood Lumber Standard
- Standard Grading Rules for Canadian Lumber (Para. 820b Standard sizes)
- EN 336 and UK customary sizes
- Implications of NCC 2016 changes for mid-rise timber buildings on supply of sawn softwood (PRA391-1516)
- Wood Handbook (FPL-GTR-282), Chapter 5: Mechanical Properties of Wood (Table 5-3b)
- 2021 International Residential Code, Chapter 6: Wall Construction (R602 studs, plates, headers)
- 2021 International Residential Code, Chapter 5: Floors (R502 joists, R507 decks)
- DCA 6: Prescriptive Residential Wood Deck Construction Guide (2015 IRC basis)