Lumber Size Chart(Nominal vs Actual Dimensions)

The definitive guide to wood sizes for carpenters, contractors, and makers. Stop guessing why your 2x4 isn't 2 inches by 4 inches. Get actual dimensions for softwood, hardwood, and sheet goods in one printable chart.

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Framing Softwood

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Dimensional Lumber (Softwood)

Nominal vs Actual Dimensions • Letter

Nominal SizeActual (Inch)Actual (MM)Common Uses / Notes
1 x 23/4" x 1 1/2"19 x 38 mmTrim, Furring
1 x 33/4" x 2 1/2"19 x 64 mmBaseboards, Trim
1 x 43/4" x 3 1/2"19 x 89 mmTrim, Fascia
1 x 63/4" x 5 1/2"19 x 140 mmFencing, Shelving
1 x 83/4" x 7 1/4"19 x 184 mmShelving, Siding
1 x 103/4" x 9 1/4"19 x 235 mmTrim, Shelving
1 x 123/4" x 11 1/4"19 x 286 mmStair treads, Shelving
2 x 21 1/2" x 1 1/2"38 x 38 mmBalusters, Framing
2 x 31 1/2" x 2 1/2"38 x 64 mmFraming
2 x 41 1/2" x 3 1/2"38 x 89 mmWall Studs, Framing
2 x 61 1/2" x 5 1/2"38 x 140 mmJoists, Rafters
2 x 81 1/2" x 7 1/4"38 x 184 mmFloor Joists
2 x 101 1/2" x 9 1/4"38 x 235 mmFloor Joists, Headers
2 x 121 1/2" x 11 1/4"38 x 286 mmStair Stringers
4 x 43 1/2" x 3 1/2"89 x 89 mmPosts
4 x 63 1/2" x 5 1/2"89 x 140 mmPosts, Beams
6 x 65 1/2" x 5 1/2"140 x 140 mmHeavy Posts

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Type

Softwood

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Quality

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How to Use This Chart

Avoid the most common beginner mistake: measuring based on the label instead of the lumber.

Nominal vs Actual

Understand why a 2x4 isn't 2"x4". It starts that size (Rough Cut) but shrinks during drying and planing to 1.5"x3.5".

Choose the Right Wood

Use 'Dimensional' (2x4) for framing. Use 'Hardwood' (4/4, 8/4) for fine furniture. Use 'Sheet Goods' for cabinets.

Measure for Projects

Always design with ACTUAL dimensions. Three 2x4s side-by-side measure 4.5", not 6". Use the chart to plan precise cuts.

Common Applications

Which wood goes where? A quick guide to standard uses.

🏠

Home Framing

Structural lumber sizes (2x4, 2x6, 2x10) are standard for wall studs, floor joists, and headers.

  • Studs: 2x4 or 2x6
  • Joists: 2x8, 2x10, 2x12
  • Posts: 4x4, 6x6
🪑

Furniture Making

Fine woodworking uses the 'Quarter' system for thickness. 4/4 is 1" rough, surfacing to ~13/16".

  • Tabletops: 5/4 (1-1/16" finished)
  • Face Frames: 1x2 (3/4" x 1-1/2")
  • Drawer Sides: 1/2" Plywood
☀️

Decking & Outdoor

Pressure-treated lumber is often swollen from moisture. A fresh 2x6 deck board might measure fuller than a kiln-dried one.

  • Deck Boards: 5/4 x 6
  • Posts: 4x4 or 6x6
  • Account for shrinkage gaps

Lumber Sizing Systems Explained

Different trades speak different languages. Here's how to translate them.

Construction

Dimensional (Softwood)

Used for construction (Pine, Fir). Nominal size (2x4) refers to rough cut. Actual size is always smaller (1.5 x 3.5).

Fine Woodworking

Hardwood (Quarter System)

Used for furniture (Oak, Walnut). Measured in quarters of an inch. 4/4 = 1 inch, 8/4 = 2 inches (Rough thickness).

Cabinetry

Sheet Goods (Plywood)

Sold as 4x8 sheets. Nominal 3/4" plywood is often 23/32" actual thickness. Always measure before cutting dados.

Frequently Asked Questions

Common questions about wood dimensions.

Is a 2x4 really 2 inches by 4 inches?
No. It is nominally 2x4 (rough cut), but after drying and surfacing, it measures 1-1/2" x 3-1/2". Always measure actual dimensions for construction.
What is a 'board foot'?
A volume measurement for pricing hardwood. 1 Board Foot = 144 cubic inches (e.g., 12" wide x 12" long x 1" thick).
Why is plywood 23/32" instead of 3/4"?
Sanding during manufacturing removes material. Most '3/4 inch' plywood is actually 23/32" or roughly 18mm. Cabinet makers must measure actual thickness for dado joints.
Does pressure-treated wood have different dimensions?
Theoretically no, but because it is infused with chemicals and water, it is often swollen and slightly larger/heavier until it dries out completely.
What does S4S mean?
Surfaced 4 Sides. It means the board has been planed smooth on all four faces (two faces, two edges). Dimensional lumber is typically S4S.
What are 4/4 and 8/4 dimensions?
This is the 'Quarter' system for rough hardwood thickness. 4/4 = 4 quarters of an inch (1 inch). 8/4 = 8 quarters (2 inches). Surfaced thickness will be about 3/16" to 1/4" less.