Stack of dimensional lumber showing the board ends

Reference

Lumber actual sizes: what a 2x4 really measures

The name on the bin is the nominal size — roughly the rough-sawn size before drying and planing. Those take ¼ to ¾ inch off each dimension before the board reaches the store, and every framing table, span chart and deck calculator uses the smaller, dressed number.

What is the actual size of a 2x4? 1½ × 3½ inches (38 × 89 mm). A 2x6 is 1½ × 5½, a 4x4 is 3½ × 3½.

Nominal vs actual lumber sizes (2x4, 2x6, 4x4)

Softwood lumber in the US is dressed to the sizes in the American Softwood Lumber Standard. One-by boards lose a quarter inch of thickness; two-by and thicker lose half an inch; widths lose half an inch up to 6 in nominal and three-quarters above that. Green (undried) lumber is dressed slightly larger — a green 2x4 is 1⁹⁄₁₆ × 3⁹⁄₁₆ in — and rough-sawn lumber is close to the full nominal size, which is why a board from a sawmill measures bigger than one from the store.

Nominal	Actual, inches	Actual, mm
1x2	¾ × 1½	19 × 38
1x3	¾ × 2½	19 × 64
1x4	¾ × 3½	19 × 89
1x6	¾ × 5½	19 × 140
1x8	¾ × 7¼	19 × 184
1x10	¾ × 9¼	19 × 235
1x12	¾ × 11¼	19 × 286
2x2	1½ × 1½	38 × 38
2x3	1½ × 2½	38 × 64
2x4	1½ × 3½	38 × 89
2x6	1½ × 5½	38 × 140
2x8	1½ × 7¼	38 × 184
2x10	1½ × 9¼	38 × 235
2x12	1½ × 11¼	38 × 286
4x4	3½ × 3½	89 × 89
4x6	3½ × 5½	89 × 140
6x6	5½ × 5½	140 × 140

Standard lumber lengths

Dimensional lumber is sold in 2 ft steps from 8 to 24 feet: 8, 10, 12, 14, 16, 18, 20, 22, 24. Home Depot and Lowe's stock 8, 10, 12 and 16 ft in most sizes; the other lengths are a lumberyard order. Studs come pre-cut at 92⅝ in for an 8 ft wall, 104⅝ in for 9 ft and 116⅝ in for 10 ft.

Lumber weight per foot

How much does a 2x4 weigh? About 8 lb for an 8 ft kiln-dried spruce-pine-fir board, 17 lb wet and pressure-treated. Weight is density times the dressed cross-section, and density moves with the species and far more with moisture: fresh pressure-treated pine can weigh twice what a kiln-dried spruce-pine-fir board of the same size weighs.

Spruce-pine-fir, kiln-dried (about 12% MC)

Size	Per foot	8 ft board	16 ft board	Per meter
2x4	1.0 lb	8 lb	16 lb	1.49 kg
2x6	1.6 lb	13 lb	26 lb	2.38 kg
2x8	2.1 lb	17 lb	34 lb	3.13 kg
2x10	2.7 lb	22 lb	43 lb	4.02 kg
2x12	3.3 lb	26 lb	53 lb	4.91 kg
4x4	2.4 lb	19 lb	38 lb	3.57 kg
6x6	5.9 lb	47 lb	94 lb	8.78 kg

Douglas fir-larch, kiln-dried (about 12% MC)

Size	Per foot	8 ft board	16 ft board	Per meter
2x4	1.2 lb	10 lb	19 lb	1.79 kg
2x6	1.9 lb	15 lb	30 lb	2.83 kg
2x8	2.6 lb	21 lb	42 lb	3.87 kg
2x10	3.3 lb	26 lb	53 lb	4.91 kg
2x12	4.0 lb	32 lb	64 lb	5.95 kg
4x4	2.9 lb	23 lb	46 lb	4.32 kg
6x6	7.1 lb	57 lb	114 lb	10.57 kg

Southern yellow pine, kiln-dried (about 12% MC)

Size	Per foot	8 ft board	16 ft board	Per meter
2x4	1.4 lb	11 lb	22 lb	2.08 kg
2x6	2.2 lb	18 lb	35 lb	3.27 kg
2x8	2.9 lb	23 lb	46 lb	4.32 kg
2x10	3.7 lb	30 lb	59 lb	5.51 kg
2x12	4.5 lb	36 lb	72 lb	6.70 kg
4x4	3.2 lb	26 lb	51 lb	4.76 kg
6x6	8.0 lb	64 lb	128 lb	11.91 kg

Pressure-treated southern pine, wet from treatment

Size	Per foot	8 ft board	16 ft board	Per meter
2x4	2.1 lb	17 lb	34 lb	3.13 kg
2x6	3.3 lb	26 lb	53 lb	4.91 kg
2x8	4.3 lb	34 lb	69 lb	6.40 kg
2x10	5.5 lb	44 lb	88 lb	8.18 kg
2x12	6.7 lb	54 lb	107 lb	9.97 kg
4x4	4.8 lb	38 lb	77 lb	7.14 kg
6x6	12.0 lb	96 lb	192 lb	17.86 kg

Plywood and OSB sheet weight

A standard 4 × 8 ft sheet, by thickness. OSB is denser than plywood of the same thickness.

Panel	Thickness	4 × 8 sheet	kg
Plywood	1/4 in	26 lb	11.8
	3/8 in	35 lb	15.9
	1/2 in	48 lb	21.8
	5/8 in	58 lb	26.3
	3/4 in	68 lb	30.8
OSB	7/16 in	47 lb	21.3
	1/2 in	53 lb	24.0
	5/8 in	68 lb	30.8
	3/4 in	80 lb	36.3

The deck calculator counts boards, joists and posts at these dressed sizes.

Plan your deck →

Figures: Nominal and dressed sizes: American Softwood Lumber Standard, Voluntary Product Standard PS 20-20, Table 3 (dry and green dressed sizes). Standard lengths: PS 20, WWPA and SPIB grading rules — dimension lumber in 2 ft steps, normally 8 to 24 ft. Weights per foot: USDA Forest Products Laboratory Wood Handbook (FPL-GTR-282) and NDS Supplement specific gravities at about 12% moisture content — spruce-pine-fir about 28 lb/ft³, Douglas fir-larch 34, southern yellow pine 38 — multiplied by the dressed cross-section; wet pressure-treated southern pine at about 57 lb/ft³ from Southern Forest Products Association and treater shipping weights (an 8 ft 2x4 at 15–18 lb). Panel weights: APA Engineered Wood Construction Guide (Form E30) design weights, plywood 0.8–2.1 lb/ft² and OSB 1.5–2.5 lb/ft² by thickness. Pre-cut stud lengths: retailer stud listings; the 1964 dressed-size change: PS 20 history. Accessed 2026-10-14. Weights are planning figures — moisture content on the day moves them by a third or more.

Lumber size questions

How much does a 2x4 weigh?

A kiln-dried spruce-pine-fir 2x4 weighs about 8 lb at 8 ft; pressure-treated and wet, about 17 lb.

How much does a 2x6 weigh?

About 13 lb for an 8 ft kiln-dried spruce-pine-fir 2x6 and about 26 lb for an 8 ft wet pressure-treated one; a 16 ft treated 2x6 is about 53 lb.

Is a 4x4 really 4 inches?

No — it is 3½ × 3½ in. Post bases and brackets are made for that size.

Why is a 2x4 not 2 by 4?

The nominal size is roughly the rough-sawn dimension before drying and surfacing. The standard dressed size has been 1½ × 3½ since 1964.

How long is a 2x4?

Stock lengths are 8, 10, 12, 14, 16, 18, 20, 22, 24 ft, plus pre-cut studs at 92⅝, 104⅝ and 116⅝ in for 8, 9 and 10 ft walls.

The rest of the deck

These tables set how far the frame can reach. Every deck tool on the site works inside them.

Tools for the job

What makes this job easier

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