2x4 Actual Size

How to use this lumber size chart

1. Pick your nominal size. The buttons are grouped by type — 1× boards, 5/4 decking, 2× dimensional lumber, and posts & timbers. Tap the size you buy it by (the “2×4” on the tag), and the card shows what it actually measures.
2. Read the real dimensions. You get the dressed size three ways: in fractions the way a tape reads it (1½ × 3½), in decimal inches, and in millimeters and centimeters for metric plans and tool setups.
3. See it to scale. The end-grain diagram draws the nominal size as a dashed outline and the actual board as the solid bar inside it — so you can see exactly how much gets planed away.
4. Set the length for board feet and weight. Choose a stock length (or type a custom one) to get the board-foot count for pricing and an estimated weight. Switch species and toggle kiln-dried vs. green, because a wet or treated board weighs far more.
5. Save or share it. Download a branded PDF with the full nominal-vs-actual reference table for the truck, or copy a link with your exact selection baked in to hand to a helper or the lumber desk.

Why this 2x4 size tool is different

Search “2x4 actual size” and you get a stack of static images, trade-association explainer articles, and Reddit threads — all of which tell you a 2×4 is 1½ × 3½ and stop there. This tool goes further:

• It’s interactive — the top results aren’t. Every size in one place: tap 2×6, 1×8, 4×4, or 5/4 decking and the numbers, the metric conversion, and the scale diagram all update instantly. No scrolling through a JPEG looking for your row.
• It shows the shrink to scale. The cross-section draws the actual board inside a dashed ghost of the nominal size, so the “where did my half inch go” question is answered visually, not just in a table.
• Metric built in. Inches, fractions, and millimeters/centimeters — the conversion woodworkers outside the US and anyone setting a metric tool fence actually need.
• It carries the numbers into the job. Board feet for pricing and estimated weight for hauling and load math are one click away, with a species and moisture toggle because a green pressure-treated 2×4 can weigh double a dry one.
• One printable, cited reference. The PDF is the whole nominal-vs-actual table on one page, sourced to the U.S. lumber standard — tape it inside a shop cabinet instead of bookmarking five different pages.
• Embeddable. If you run a woodworking blog, a shop-class site, or a building resource, the iframe at the bottom hosts the same interactive chart with attribution. Nobody else ranking for this term offers one.

Why a 2x4 isn’t 2×4 (and how the numbers work)

Lumber is named by its nominal size — the rough dimension when it’s first sawn from the green log. Before it’s sold, it’s dried and run through a planer (“surfaced four sides,” or S4S) to make it straight, smooth, and uniform. That planing shaves material off every face, so the finished actual size is smaller than the name. The amounts are standardized in the United States by Voluntary Product Standard PS 20, the American Softwood Lumber Standard, so a 2×4 measures the same 1½ × 3½ whether you buy it in Maine or Arizona.

The pattern is simple once you see it:

Nominal 1 in thick        ->  actual 3/4 in
Nominal 2 to 6 in         ->  actual 1/2 in smaller   (2->1.5, 4->3.5, 6->5.5)
Nominal 8 in and wider    ->  actual 3/4 in smaller   (8->7.25, 10->9.25, 12->11.25)
5/4 (five-quarter) deck   ->  actual a full 1 in thick

Millimeters   = actual inches x 25.4
Board feet    = nominal thickness x nominal width x length(ft) / 12
Weight (est.) = actual cross-section (in^2) / 144 x length(ft) x species density (lb/ft^3)

Two things trip people up. First, board feet use the nominal size, not the actual — a 2×4×8 is priced as 5.33 board feet even though it’s really 1½ × 3½. Second, weight depends on moisture as much as species: a kiln-dried SPF 2×4×8 is around 8–9 lb, but the same board green or pressure-treated can be 15–17 lb. That’s why the tool has a species picker and a kiln-dried/green toggle.

Full nominal vs. actual lumber size chart

The dressed (S4S, dry) sizes for every common softwood size, in inches and millimeters:

These are surfaced-dry sizes (≤19% moisture content), which is what you buy at a lumberyard or home center. Rough-sawn lumber from a sawmill runs full or nearly full size, and lengths (8, 10, 12, 14, 16 ft) are sold true — a 2×4×8 really is 8 feet long.

Three times the actual size matters

The 2×4 wall that’s really 3½ inches deep

Framing a stud wall, you plan drywall and wiring around a “4-inch” wall — but a 2×4 wall is 3½ inches of stud plus ½ inch of drywall each side, about 4½ inches finished. Electrical boxes, door jambs, and window bucks are all sized to that real 3½, not to 4. Get the nominal-vs-actual wrong and your jambs don’t reveal evenly. If you’re about to frame, our circular saw picks and miter saw guide cover the two saws that do 90% of stud work.

Stacking 2×10 joists to a real depth

Sizing a floor for headroom below, a 2×10 joist is not 10 inches deep — it’s 9¼. Across a doubled beam and subfloor, those missing three-quarter inches add up fast when you’re fighting a tight basement ceiling or matching an existing floor. The chart’s actual-depth number is the one that goes on your section drawing.

Hauling pressure-treated 6×6 posts

A 6×6 is a full-feeling 5½ × 5½, and treated posts are sold soaking wet. An 8-foot treated 6×6 can top 60 lb apiece — set the tool to Southern Yellow Pine, green, and you’ll see why you want a helper (and why the bed of the truck sits low). Cutting them clean to length is a job for a good sliding miter saw; a standard 10-inch saw won’t clear a 6×6 in one pass.

What affects the real size

The standard sizes above are exact by definition, but a few things move the number in the real world:

• Moisture. Wood shrinks as it dries and swells when it takes on water. The 1½ × 3½ standard is set at ≤19% moisture; a board still wet from the yard can measure a hair over, and a kiln-dried board in a dry house a hair under.
• Rough-sawn vs. surfaced. Lumber straight off a sawmill blade (“rough” or “full-sawn”) is close to its nominal size — a rough 2×4 really can be near 2 × 4. Only surfaced (S4S) lumber follows the dressed sizes in the chart.
• Species and grade. The dimensions are the same across species, but denser species (Southern Yellow Pine, Douglas Fir) hold an edge better and weigh more than lighter SPF or cedar at the same size.
• Pressure treatment. Treatment forces liquid into the wood, so treated lumber leaves the store heavy and wet, then shrinks slightly as it dries in place. Buy it a touch oversized for critical fits.
• Nominal 5-inch-plus timbers. Large posts and beams (“5 inches and thicker”) are surfaced ½ inch under, so a 6×6 is 5½ × 5½ — not the ¾-inch reduction the wide boards get.

Frequently asked questions

What is the actual size of a 2x4?

A 2×4 actually measures 1½ inches by 3½ inches (1.5 × 3.5 in, or about 38 × 89 mm). The “2×4” is the nominal size — the rough dimension before the board is dried and planed smooth. The planing removes about a half inch from both the thickness and the width, and the result is standardized nationwide, so every S4S 2×4 is the same 1½ × 3½.

Is a 2x4 really 2 inches thick?

No. A 2×4 is 1½ inches thick, not 2. It starts near a full 2 inches when it’s rough-sawn from the green log, but drying and surfacing four sides shaves it down to the finished 1½-inch thickness you buy at the store. The only time a 2×4 is close to a true 2 inches is if it’s rough-sawn (unsurfaced) lumber from a sawmill.

Is a 2x4x8 actually 8 feet long?

Yes. Length is sold true — the “8” in a 2×4×8 means a full 8 feet (96 inches). Only the thickness and width are reduced by surfacing; the length is not. So a 2×4×8 is genuinely 1½ × 3½ inches by 8 feet. (Pre-cut wall studs are the exception — they’re cut to 92⅝ inches so that with plates they frame a standard 8-foot wall.)

How many board feet is a 2x4?

Board feet are figured from the nominal size: thickness × width × length-in-feet ÷ 12. A 2×4×8 is 2 × 4 × 8 ÷ 12 = 5.33 board feet, and a 2×4×10 is 6.67. Board footage always uses the nominal 2 × 4, not the actual 1½ × 3½ — that’s the lumber-industry convention for pricing, and it’s what the tool above calculates when you set a length.

Why are 2x4s smaller than 2x4?

Because the name refers to the size before finishing. Green lumber is sawn to a full 2 × 4, then dried to stabilize it and surfaced on all four sides to make it straight, smooth, and consistent — and that milling removes material. Keeping the “2×4” name after milling is a century-old convention; the actual dimensions were standardized in the U.S. so every mill’s 2×4 matches. It’s the same reason a 1× board is ¾ inch thick and a 4×4 is 3½ × 3½.

Can I embed this lumber chart on my site?

Yes — copy the iframe snippet at the bottom of this page. The embedded version is a streamlined interactive chart built for woodworking and DIY blogs, shop-class and vocational-education pages, building-science and maker resources, and forums. Required attribution is included in the snippet. Free, no signup, no analytics attached to the embed.

Related tools

• Lumber Calculator — counts the studs, plates, headers, joists, and board feet for a whole wall, floor, or deck, with a printable shopping list
• Fence Calculator — posts, rails, pickets, and concrete for any fence, using the real post and rail sizes
• Retaining Wall Calculator — full block, base, and drainage BOM for a segmental wall
• Roof Square Footage Calculator — area, squares, and bundles from your footprint and pitch
• Browse all free tools by Jake →

Gear for cutting lumber to size

Knowing the real dimensions is step one; cutting to them cleanly is step two. Here’s the kit Jake reaches for when a stack of 2×4s becomes a project:

• Best Circular Saws — the versatile first saw: breaks down sheet goods and crosscuts framing anywhere on the job, no bench required.
• Best Miter Saws — fast, dead-square cuts to length on studs, trim, and posts. A sliding model handles wide 2× stock and 6×6 timbers.
• Best Table Saws — for ripping boards to a precise, repeatable width, the accurate way to turn one wide board into several narrow ones.
• Best Hand Tool Sets — a quality tape, speed square, and marking knife are what make every cut land on the line. The foundation of accurate work.

New to all of this? Start with our beginner’s guide to power tools — it walks through which saws and drills to buy first and how to use them safely.

Sources & methodology

• U.S. DOC / NIST Voluntary Product Standard PS 20 — American Softwood Lumber Standard (dressed/S4S dry sizes)
• Western Wood Products Association (WWPA) — Lumber Sizes (nominal vs. dressed, dry)
• American Wood Council (AWC) — National Design Specification / dimensional lumber standard sizes
• USDA Forest Products Laboratory — Wood Handbook (Ch. 4, density & specific gravity by species)
• Inch Calculator — Lumber weight cross-check (green vs. kiln-dried)

Actual dimensions are the surfaced-dry (S4S) sizes standardized by U.S. DOC/NIST PS 20; board-foot and weight math is described in the “How it works” section above. Weight uses as-sold density values consistent with the USDA Wood Handbook and is an estimate. Reviewed against the standard annually. About Jake · Last reviewed July 10, 2026.

Embed this chart on your site

Free for woodworking and DIY blogs, shop-class and vocational sites, maker and building-science resources, and forums. Required attribution is built into the snippet. No fee, no account, no analytics attached to the embed.

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