Dimensional lumber is cut to a specific length, width, and depth. However, there is a difference between the nominal size (what the lumber is referred to) and the actual size. The tables below provide both the nominal and actual sizes so many common North American lumber sizes.

Softwood Lumber Dimensions

Softwood lumber is generally used for framing walls and floors. In the United States, softwood lumber is governed by the National Institute of Standards American Softwood Lumber Standard (PS 20).

North American Standard 1-by Lumber

Nominal Size (inches) Actual Size (inches) Actual Size (mm)
1 x 2 3/4 x 1 1/2 19 x 38
1 x 3 3/4 x 2 1/2 19 x 64
1 x 4 3/4 x 3 1/2 19 x 89
1 x 6 3/4 x 5 1/2 19 x 140
1 x 8 3/4 x 7 1/4 19 x 140
1 x 10 3/4 x 9 1/4 19 x 184
1 x 12 3/4 x 11 1/4 19 x 286

North American Standard 2-by Lumber

Nominal Size (inches) Actual Size (inches) Actual Size (mm)
2 x 2 1 1/2 x 1 1/2 38 x 38
2 x 3 1 1/2 x 2 1/2 38 x 64
2 x 4 1 1/2 x 3 1/2 38 x 89
2 x 6 1 1/2 x 5 1/2 38 x 140
2 x 8 1 1/2 x 7 1/4 38 x 184
2 x 10 1 1/2 x 9 1/4 38 x 235
2 x 12 1 1/2 x 11 1/4 38 x 286
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North American Standard 3-by Lumber

Nominal Size (inches) Actual Size (inches) Actual Size (mm)
3 x 3 2 1/2 x 2 1/2 64 x 64
3 x 4 2 1/2 x 3 1/2 64 x 89
3 x 6 2 1/2 x 5 1/2 64 x 140
3 x 8 2 1/2 x 7 1/4 64 x 184
3 x 10 2 1/2 x 9 1/4 64 x 235
3 x 12 2 1/2 x 11 1/4 64 x 286

North American Standard 4-by Lumber

Nominal Size (inches) Actual Size (inches) Actual Size (mm)
4 x 4 3 1/2 x 3 1/2 89 x 89
4 x 6 3 1/2 x 5 1/2 89 x 140
4 x 8 3 1/2 x 7 1/4 89 x 184
4 x 10 3 1/2 x 9 1/4 89 x 235
4 x 12 3 1/2 x 11 1/4 89 x 286

North American Standard 6-by Lumber

Nominal Size (inches) Actual Size (inches) Actual Size (mm)
6 x 6 5 1/2 x 5 1/2 140 x 140

North American Standard 8-by Lumber

Nominal Size (inches) Actual Size (inches) Actual Size (mm)
8 x 8 7 1/4 x 7 1/4 184 x 184

Softwood Lumber Lengths

Softwood lumber comes in a number of standard lengths as listed in the table below.

Length in Feet Length in Inches Length in Meters
6 feet 72 inches 1.829 meters
8 feet 96 inches 2.438 meters
10 feet 120 inches 3.048 meters
12 feet 144 inches 3.658 meters
14 feet 168 inches 4.267 meters
16 feet 192 inches 4.877 meters
18 feet 216 inches 5.486 meters
20 feet 240 inches 6.096 meters
22 feet 264 inches 6.706 meters
24 feet 288 inches 7.315 meters
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Hardwood Lumber Dimensions

Hardwood lumber is sized based on how many sides are surfaced. Surfaced refers to a finishing process that smooths the lumber to remove all saw marks.

In North America, hardwood lumber is usually specified using the quarter system, where a board is identified by its thickness in quarters of an inch. For instance, hardwood trim that ends up being just over 1" thick (surfaced on 2 sides) is called a five-quarter (5/4) board.

Hardwood board widths vary. In most cases, hardwood boards come in random widths to be ripped to size by the woodworker. However, in some cases, like the big-box hardware stores, the boards come in dimensional widths similar to softwood widths. It is advisable to check with your contractor or lumber supplier before finalizing design details so you aren't surprised by what you receive.

Nominal Size Rough Size Actual Size: Surfaced 1 Side Actual Size: Surfaced 2 Sides
1/2 inch 3/8 inch (9.5 mm) 5/16 inch (7.9 mm)
5/8 inch 1/2 inch (13 mm) 7/16 inch (11 mm)
3/4 inch 5/8 inch (16 mm) 9/16 inch (14 mm)
4/4 inch 1 inch 7/8 inch (22 mm) 13/16 inch (21 mm)
5/4 inch 1 1/4 inch 1 1/8 inch (29 mm) 1 1/16 inch (27 mm)
6/4 inch 1 1/2 inch 1 3/8 inch (35 mm) 1 5/16 inch (33 mm)
8/4 inch 2 inches 1 13/16 inch (46 mm) 1 3/4 inch (44 mm)
12/4 inch 3 inches 2 13/16 inch (71 mm) 2 3/4 inch (70 mm)
16/4 inch 4 inches 3 13/16 inch (97 mm) 3 3/4 inch (95 mm)

Lumber Manufacturers

The links below will take you to Archimat, our building product directory, which hosts a list of manufacturers.

Wood / Plastics / Composites
Rough Carpentry
Finish Carpentry
Wood Decking

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