So what actually is the size of a 2x4? (2024)

The most well-known piece of lumber is the 2x4, pronounced two-by-four. It’s mostly used in the framing of houses but you’ll also see it in just about any other construction or DIY project.

But there is a caveat will calling a 2x4 a 2x4: It’s not really two inches by four inches as its name implies. A 2x4 is actually 3-½ inches by 1-½ inches. Many of you know this, but why is this a thing? You don’t go to Subway and pay for a $5-footlong expecting to get 11 inches (although many of you will argue this is the case). And it’s not just a 2x4: A 1x4 is actually ¾ inches by 3-½ inches; a 4x4 is actually 3-½ inches by 3-½ inches. Most of us that know about this dimensional discrepancy will say “This is how it has always been.”

So what actually is the size of a 2x4? (1)

But there is a reason. Put simply, the discrepancy in sizing comes from the need for the lumber industry to stay competitive with other market alternatives during times of scarcity.

Before mass production of lumber and wood started around 1870, trees were cut and made to order for carpenters. Sizes always varied, which left final sizing measurements up to the builders on site. Trees were grown and used locally and many people in the industry viewed lumber and forests as an unlimited resource in the U.S.

But as the population in the United States grew, so did building. And these once “unlimited” resources were starting to become scarce. Prime forestland was concentrated around major U.S. cities like New York, Boston, Baltimore, and Philadelphia as these areas were transportation hubs. But these forests around these cities were becoming clear.

With resources in these areas becoming scarce, other areas of the country saw this as an opportunity to enter the market. The advent of the railroad made it possible for other cities to ship lumber to different parts of the country. Cities like Chicago, Albany, NY, and Bangor, ME became lumber capitals of the country.

So what actually is the size of a 2x4? (2)

Competition occurred among regions, or more specifically, among species. For example, southern pine forests called “pineries” consisting of shortleaf pine, slash pine, longleaf pine, loblolly pine, and other less common species (collectively known as southern yellow pine, SYP) competed against western Douglas fir, western hemlock, and spruce forests.

At the turn of the 20th century, lumber was commonly sold as “free on board” or FOB, meaning the purchaser was responsible for shipping. According to the U.S. Department of Agriculture’s “History of Yard Lumber Size Standards,” shipping charges, determined by distance traveled and weight, doubled the cost of lumber. Thus, the density and moisture of wood began to have a big impact on forestry economics. People in the industry preferred thinner, lighter sizes for longer hauls. They produced optimal finished sizes of preferred species by kiln drying to control moisture content.

So what actually is the size of a 2x4? (3)

There were other factors that played a role in moving towards smaller sizes: The same technology used to power steam engine trains was now being used in the newly invented circular saw, made to achieve faster, continuous cuts in the sawmill. This development went hand-in-hand with the evolution of framing building. Wood was no longer cut from trees and shipped directly to a job site. Small dimension stock, like the 2x4, was now being used more and more.

And with the increased use of “common” lumber, the need for a uniformed sizing became apparent. As retail lumberyards pushed for more regulated measurements and standards, trade associations were formed. And in April 1919, attendees of the first American Lumber Congress called for size and terminology standardization. Although disagreement about specific language persisted for decades.

Then came World War II. The demand for pallets and crates for the war caused a shortage in wood for the lumber industry. Builders began to use alternatives to wood such as concrete block and engineered products (like plywood). People in the forest industry were under immense pressure to figure out how to become more efficient and compete. The lack of resources forced a compromise because thinner 2x4s were a way to compete with these alternatives in the industry.

So what actually is the size of a 2x4? (4)

In 1964, size standards, maximum moisture content, and naming were agreed upon. The nominal 2x4 thus became the actual 1-½ x 3-½ inch board. People in the industry were able to sell “2x4s” with 34% less volume at a lower price to compete with alternatives. Today, we still follow this standard and it is widely accepted in the building industry.

In 2017 and 2018, lawsuits against Home Depot and Menards challenged this standard, saying that the common lumber sizing was misleading for consumers. But a judge dismissed both claims.

So the next time you go to your local retail lumber spot (hopefully Nelson-Young) and order up a few 2x4s, take a moment to think about the actual dimensions you’re getting. You know this is how it has always been - but now you know why.

If you want to know common lumber dimensions, here’s a link to more information on our website:

So what actually is the size of a 2x4? (2024)


What size is a 2x4 actually? ›

The true measurement of a 2x4 is actually about 1.5″ x 3.5″. When the board is first rough sawn from the log, it is a true 2x4, but the drying process and planning of the board reduce it to the finished 1.5″ x 3.5″ size.

Why doesn t a standard 2x4 piece of wood actually measure 2 inches by 4 inches? ›

That means that a 2×4 piece of lumber was cut at the sawmill from a green log, and measured 2” by 4” at the time of cutting. However, as the wood dries out and cures, it shrinks. That means that the 2×4 cut green doesn't meet the same dimensions after it's cured due to shrinkage.

What is 2x4 only 1.5 x3 5? ›

The 2x4 was originally called that because they were rough sawed at an actual 2x4 inches and air dried. As kiln drying became the norm they were sawed so as to be 1.625x3. 625 when they finished drying. Since the early 70s this has been reduced to 1.5x3.

What does the true size of lumber mean? ›

True or Actual Size Wood

Rough cut is when lumber has been cut to a specific size but has not been smoothed out during the milling process, and therefore has a rough surface with saw marks.

Are 2x4 actually 8 ft? ›

Typical 2x4 studs are 8 feet (96 inches, 2.44 meters) long, or somewhat shorter to make a finished wall just over 8 feet tall when combined with a single bottom plate and double top plate.

Is a 2x4 really 8 feet long? ›

If you see a third number (e.g. 2x4x8), that number is length. Thickness and width are measured in inches, while length is measured in feet. So 2x4x8 is two inches thick by four inches wide, and the board itself is eight feet long.

Why are 2x4 not true to size? ›

Newly-sawn lumber, such as a 2×4, is soaking wet before kiln drying. It then shrinks as it's dried and is further reduced in size after being planed from “rough” to “surfaced” lumber. As to lengths, an 8″, 10″, 12″ etc. foot length always measures as stated.

Why are 2x4 not actual size? ›

In 1964, size standards, maximum moisture content, and naming were agreed upon. The nominal 2x4 thus became the actual 1-½ x 3-½ inch board. People in the industry were able to sell “2x4s” with 34% less volume at a lower price to compete with alternatives.

Why is lumber not true to size? ›

Before it's ready to be sold, dimensional lumber is dried and then planed to make it smooth. Wood shrinks as it dries and the planing or surfacing process removes some of the original material. This means that the wood's actual measurements are now different from the nominal measurements.

Does a 2x4 actually measure 2x4? ›

Now, most timber is milled and planed to give it a little more of a finished look, and a little more of a consistent size and profile. Because of this extra milling, a 2x4 no longer measures a full 2 inches by four inches. Instead, a 2x4 is really only 1 1/2" by 3 1/2".

What is 2x4 nominal actual? ›

Lumber Dimensions
NominalActualActual - Metric
2" x 4"1-1/2" x 3-1/2"38 x 89 mm
2" x 6"1-1/2" x 5-1/2"38 x 140 mm
2" x 8"1-1/2" x 7-1/4"38 x 184 mm
2" x 10"1-1/2" x 9-1/4"38 x 235 mm
24 more rows

When did lumber stop being true to size? ›

When did lumber dimensions change from actual to nominal? The size of lumber before around 1970 was 3/8″ less than nominal (a 2x4 was 1 5/8″ x 3 5/8″), after around 1970 it became 1/2″ less than nominal (a 2x4 was 1 1/2″ x 3 1/2″).

What is the most common lumber size? ›

The most commonly used lumber, structural lumber, are the 2-inch x 4-inch and 4-inch x 4-inch boards used in everyday DIY and construction projects. Framing and structural lumber follows standard building dimensions (thickness and width). Standard dimensions allow for faster building as less cutting is needed on site.

Why is a 2x6 not 2x6? ›

2x4 and 2x6 boards lose 1/2 inch in thickness and 1/2 inch in width before leaving the mill. That means a 2 x 4 board is actually 1-1/2 inches by 3-1/2 inches. The larger 2x boards (2x8, 2x10, etc.) lose 3/4 inch in width.

Is a 2x4 really 2 inches? ›

A piece of surfaced (sanded smooth) 2x4 lumber actually measures 1½ inches thick and 3½ inches wide. In rough-cut condition, a 2x4 is slightly less than 2 inches thick and approximately 4 inches wide. When wood is milled from a rough to a smooth surface, it loses about ¼-inch from each of its four sides.

What are the actual dimensions of 2x4x8 lumber? ›

Actual Product Length (ft.)8 ft1.5 in
Actual Product Width (in.)3.5 in2x4
Nominal Product Length (ft.)8 ft2 in
Nominal Product Width (in.)4 in

What is the difference between nominal and actual size? ›

Lumber sizes are usually given in "nominal" measurements. The nominal measurements are a board's size before it has been planed smooth (surfaced) on all four sides. The actual measurements are the final size of your piece of lumber.


Top Articles
Latest Posts
Article information

Author: Van Hayes

Last Updated:

Views: 5430

Rating: 4.6 / 5 (46 voted)

Reviews: 93% of readers found this page helpful

Author information

Name: Van Hayes

Birthday: 1994-06-07

Address: 2004 Kling Rapid, New Destiny, MT 64658-2367

Phone: +512425013758

Job: National Farming Director

Hobby: Reading, Polo, Genealogy, amateur radio, Scouting, Stand-up comedy, Cryptography

Introduction: My name is Van Hayes, I am a thankful, friendly, smiling, calm, powerful, fine, enthusiastic person who loves writing and wants to share my knowledge and understanding with you.