Nominal vs. Actual Dimensions: The listed dimensions (e.g., 2x4) are nominal sizes, not the actual physical dimensions of the lumber after milling.
Moisture Content: The weight of lumber is directly dependent on its moisture content. "Green" lumber is freshly cut and wet, "kiln dried" has been dried in a kiln to a low moisture content, and "pressure treated" lumber has been infused with chemical preservatives, which adds significant weight.

Lumber Weight Data Tables

7 rows

Weight (lb) of Green Lumber Boards by Nominal Dimension and Length
Nominal Dimension (in x in)	Length 1 ft(lb)	Length 8 ft(lb)	Length 10 ft(lb)	Length 12 ft(lb)	Length 16 ft(lb)
2 x 4	1.7	13	17	20	27
4 x 4	3.6	29	36	43	58
4 x 6	5.4	43	54	65	86
4 x 8	7.2	58	72	86	115
4 x 10	9	72	90	108	144
4 x 12	10.8	86	108	130	173
6 x 6	8.1	65	81	97	130

Source: engineeringtoolbox.com

5 rows

Weight (lb) of Kiln Dried Lumber Boards by Nominal Dimension and Length
Nominal Dimension (in x in)	Length 1 ft(lb)	Length 8 ft(lb)	Length 10 ft(lb)	Length 12 ft(lb)	Length 16 ft(lb)
2 x 4	1.3	11	13	16	21
2 x 6	2	16	20	24	32
2 x 8	2.7	21	27	32	43
2 x 10	3.3	27	33	40	53
2 x 12	4	32	40	48	64

Source: engineeringtoolbox.com

10 rows

Weight (lb) of Pressure Treated Lumber Boards by Nominal Dimension and Length
Nominal Dimension (in x in)	Length 1 ft(lb)	Length 8 ft(lb)	Length 10 ft(lb)	Length 12 ft(lb)	Length 16 ft(lb)
2 x 4	2.1	17	21	26	34
2 x 6	3.2	26	32	38	51
2 x 8	4.4	35	44	53	70
2 x 10	5.5	44	55	66	88
2 x 12	6.6	53	66	79	106
4 x 4	4.8	38	48	58	77
4 x 6	7	56	70	84	112
4 x 8	9.3	75	93	112	149
4 x 10	11.7	93	117	140	187
4 x 12	14	112	140	168	224

Green Kiln Dried Pressure Treated Lumber Weights