On a trip to your local home depot or woodworking supplier you might notice the different wood sizes on display, and be scratching your head wondering what it all means. There are a couple important things to remember when purchasing stock.
2x4 vs 1 ½”x3 ½”
The first is that 1 inch doesn’t always mean “1 inch”, so while the label might read 2x4 it actually translates to 1 ½” x 3 ½”, because of dryness and milling methods. Wood tends to shrink when it’s dried and lumber mills make adjustments accordingly. That said, the length of a piece is generally not affected so a piece “measuring” 8’ is usually very close to 96 inches.
Softwood
An important thing to remember about softwood and hardwood sizes is that they aren’t the same; softwood sizes are a lot more direct or as direct as you’d expect with the information you know now concerning 2x4’s. Most pieces of softwood used in home woodworking or construction come in 2x’s and 1x’s, but will differ slightly from the sizes advertised so for instance a 2x6 will mostly translate to a 1 ½”x5 ½” as indicated in the chart below.
| Softwood Lumber Sizes | |||
| Name | Actual | Name | Actual |
| 1x2 | 3⁄4 in × 1 1⁄2 in (19 mm × 38 mm) | 2 × 2 | 1 1⁄2 in × 1 1⁄2 in (38 mm × 38 mm) |
| 1x3 | 3⁄4 in × 2 1⁄2 in (19 mm × 64 mm) | 2 × 3 | 1 1⁄2 in × 2 1⁄2 in (38 mm × 64 mm) |
| 1x4 | 3⁄4 in × 3 1⁄2 in (19 mm × 89 mm) | 2 × 4 | 1 1⁄2 in × 3 1⁄2 in (38 mm × 89 mm) |
| 1x6 | 3⁄4 in × 5 1⁄2 in (19 mm × 140 mm) | 2 × 6 | 1 1⁄2 in × 5 1⁄2 in (38 mm × 140 mm) |
| 1x8 | 3⁄4 in × 7 1⁄4 in (19 mm × 184 mm) | 2 × 8 | 1 1⁄2 in × 7 1⁄4 in (38 mm × 184 mm) |
| 1x10 | 3⁄4 in × 9 1⁄4 in (19 mm × 235 mm) | 2 × 10 | 1 1⁄2 in × 9 1⁄4 in (38 mm × 235 mm) |
| 1x12 | 3⁄4 in × 11 1⁄4 in (19 mm × 286 mm) | 2 × 12 | 1 1⁄2 in × 11 1⁄4 in (38 mm × 286 mm) |
Hardwood
Hardwood sizing is generally a lot more complex than the relatively straightforward sizing of softwood stock. Pieces are rarely produced in standard sizes, and are generally sold by board foot by woodwork suppliers as opposed to 2x4 or 2x6 sizes. A lot depends on whether a hardwood piece has been surfaced on one side (S1S) or two sides (S2S). Judging by the chart below, a 1” stock piece might measure 7/8” if it is S1S or 13/16” if it’s S2S (surfaced on two sides). Furthermore, hardwood stock is generally sold in quarters ie ¼” thick so a 5/4 board would be 1-1/4” thick. Should your project call for stock that is 1” thick, you might want to go with a 5/4 board and whittle it down using a surface planer.
| Hardwood Lumber Sizes | ||
| Name | S1S | S2S |
| 1⁄2 in | 3⁄8 in (9.5 mm) | 5⁄16 in (7.9 mm) |
| 5⁄8 in | 1⁄2 in (13 mm) | 7⁄16 in (11 mm) |
| 3⁄4 in | 5⁄8 in (16 mm) | 9⁄16 in (14 mm) |
| 1 in or 4⁄4 in | 7⁄8 in (22 mm) | 13⁄16 in (21 mm) |
| 1 1⁄4 in or 5⁄4 in | 1+1⁄8 in (29 mm) | 1+1⁄16 in (27 mm) |
| 1 1⁄2 in or 6⁄4 in | 1+3⁄8 in (35 mm) | 1+5⁄16 in (33 mm) |
| 2 in or 8⁄4 in | 1+13⁄16 in (46 mm) | 1+3⁄4 inches (44 mm) |
| 3 in or 12⁄4 in | 2+13⁄16 in (71 mm) | 2+3⁄4 in (70 mm) |
| 4 in or 16⁄4 in | 3+13⁄16 in (97 mm) | 3+3⁄4 in (95 mm) |
Plywood
Plywood stock is graded from A-D depending on the quality of the sanded finish on both sides of the sheet where A is the smoothest. Grading is done individually for both sides, so for instance a BC plywood sheet would be graded B on one side and C for the other.
Plywood sheets are usually available as 4’x8’ sheets but remember, sizes for thickness aren’t always what they seem. While common sizes are ½” and ¾”, in reality they correspond to 15/32” and 23/32” thickness, respectively. It is important to remember that plywood is almost NEVER the thickness that it is rated at, this is so that there is room for expansion of the sheet due to moisture conditions and differences in locales.