Sawn lumber is not the actual size that you've grown up hearing. A 2x4 is not actually 2" x 4". During the finishing phase (includes drying and planing the board) the 2x4 has been reduced to 1.5" x 3.5". The following is a table describing common lumber sizes, and their actual sizes and weights (assuming the wood weighs 35 pcf). When engineering for wood design, it is important to use the actual sizes of the wood beams/columns when calculating the various dimensional properties (cross sectional area, moment of inertia, radius of gyration, etc.).

Table 1: Sawn Lumber Nominal vs Actual Size + Weights
Nominal Size Actual Size (in) Area (in2) Weight (lbs/ft)
1x3 0.75x2.5 1.88 0.47
1x4 0.75x3.5 2.63 0.64
1x6 0.75x5.5 4.13 1.00
1x8 0.75x7.25 5.44 1.32
1x10 0.75x9.25 6.94 1.69
1x12 0.75x11.25 8.44 2.05
2x3 1.5x2.5 3.75 0.94
2x4 1.5x3.5 5.25 1.28
2x6 1.5x5.5 8.25 2.00
2x8 1.5x7.25 10.88 2.64
2x10 1.5x9.25 13.88 3.37
2x12 1.5x11.25 16.88 4.10
2x14 1.5x13.25 19.88 4.83
3x3 2.5x2.5 6.25 1.52
3x4 2.5x3.5 8.75 2.13
3x6 2.5x5.5 13.75 3.34
3x8 2.5x7.25 18.13 4.41
3x10 2.5x9.25 23.13 5.62
3x12 2.5x11.25 28.13 6.84
3x14 2.5x13.25 33.13 8.05
3x16 2.5x15.25 38.13 9.27
4x4 3.5x3.5 12.25 2.98
4x6 3.5x5.5 19.25 4.68
4x8 3.5x7.25 25.38 6.17
4x10 3.5x9.25 32.38 7.78
4x12 3.5x11.25 39.38 9.57
4x14 3.5x13.25 46.38 11.28
4x16 3.5x15.25 53.38 12.98
6x6 5.5x5.5 30.25 7.35
6x8 5.5x7.5 41.25 10.03
6x10 5.5x9.5 52.25 12.70
6x12 5.5x11.5 63.25 15.37
6x14 5.5x13.5 74.25 18.05
6x16 5.5x15.5 85.25 20.72
6x18 5.5x17.5 96.25 23.29
8x8 7.5x7.5 56.25 13.67
8x10 7.5x9.5 71.25 17.32
8x12 7.5x11.5 86.25 20.96
8x14 7.5x13.5 101.25 24.61
8x16 7.5x15.5 116.25 28.26
8x18 7.5x17.5 131.25 31.90
10x10 9.5x9.5 90.25 21.94
10x12 9.5x11.5 109.25 26.55
10x14 9.5x13.5 128.25 31.17
10x16 9.5x15.5 147.25 35.79
10x18 9.5x17.5 166.25 40.41
12x12 11.5x11.5 132.25 32.14
12x14 11.5x13.5 155.25 37.73
12x16 11.5x15.5 178.25 43.33

Note: Anything greater than or equal to a: 1x8, 2x8, 3x8 or 4x8 will take 3/4" off the planing in the strong axis. All other members (including all 6x's, 8x's, 10x's, etc.) will only take a 1/2" off the planing process on both faces


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