Lumber Dimensions

2x4s are not actually 2 inches by 4 inches. When the board is first rough sawn from the log, it is a true 2x4, but the drying process and planing of the board reduce it to the finished 1.5x3.5 size. Here are the common sizes of lumber, and their actual sizes.

Nominal	Actual	Actual - Metric
1" x 2"	3/4" x 1-1/2"	19 x 38 mm
1" x 3"	3/4" x 2-1/2"	19 x 64 mm
1" x 4"	3/4" x 3-1/2"	19 x 89 mm
1" x 5"	3/4" x 4-1/2"	19 x 114 mm
1" x 6"	3/4" x 5-1/2"	19 x 140 mm
1" x 7"	3/4" x 6-1/4"	19 x 159 mm
1" x 8"	3/4" x 7-1/4"	19 x 184 mm
1" x 10"	3/4" x 9-1/4"	19 x 235 mm
1" x 12"	3/4" x 11-1/4"	19 x 286 mm
1-1/4" x 4"	1" x 3-1/2"	25 x 89 mm
1-1/4" x 6"	1" x 5-1/2"	25 x 140 mm
1-1/4" x 8"	1" x 7-1/4"	25 x 184 mm
1-1/4" x 10"	1" x 9-1/4"	25 x 235 mm
1-1/4" x 12"	1" x 11-1/4"	25 x 286 mm
1-1/2" x 4"	1-1/4" x 3-1/2"	32 x 89 mm
1-1/2" x 6"	1-1/4" x 5-1/2"	32 x 140 mm
1-1/2" x 8"	1-1/4" x 7-1/4"	32 x 184 mm
1-1/2" x 10"	1-1/4" x 9-1/4"	32 x 235 mm
1-1/2" x 12"	1-1/4" x 11-1/4"	32 x 286 mm
2" x 2"	1-1/2" x 1-1/2"	38 x 38 mm
2" x 4"	1-1/2" x 3-1/2"	38 x 89 mm
2" x 6"	1-1/2" x 5-1/2"	38 x 140 mm
2" x 8"	1-1/2" x 7-1/4"	38 x 184 mm
2" x 10"	1-1/2" x 9-1/4"	38 x 235 mm
2" x 12"	1-1/2" x 11-1/4"	38 x 286 mm
3" x 6"	2-1/2" x 5-1/2"	64 x 140 mm
4" x 4"	3-1/2" x 3-1/2"	89 x 89 mm
4" x 6"	3-1/2" x 5-1/2"	89 x 140 mm