Wood Sizes Explained: Everything You Need To Know (2024)

Confused about all the wood sizing available in stores? This is your detailed guide to understanding everything you need to know about wood sizes.

As a beginner woodworker, one of the most confusing things can be the size of the wood.

Purchasing lumber at a home improvement store or lumber yard can be intimidating enough. Then you add in the wood sizes and everything is as confusing as ever!

Wood sizing can be extremely confusing because what you see is not the exact size you buy.

The woodworking plans called for 2×4 boards which means that the boards should be 2″ x 4″ right? Wrong! They are actually 1.5″ x 3.5″. But why?! Don’t worry, we’ll get into all the details about it!

And if you end up trying to buy hardwood from a lumber yard, there are 4/4 and S2S, etc!

What are wood sizes?

When you start working on projects and reading plans, you will see boards with numbers like 1×4 (spoken as one by four), 1×6 (spoken as one by six), 2×4 (spoken as two by four), etc.

This means that a 1×4 is 1″ in thickness and 4″ in width – at least it’s supposed to be.

However, unfortunately, it is a little more complicated than that.

1×4 is the nominal size of the board. The actual sizing can be different (because wouldn’t that just be too easy?). More on that is below.

A board can be available in different lengths. The most common being 8 feet but 6 feet, 10 feet, and 12 feet are also available.

What is dimensional lumber?

Dimensional lumber is lumber that has been cut to a specific size (and shape) for use in a construction project. Dimensional lumber is the most common form of lumber used in building structures, furniture, and other woodworking projects.

Unlike rough-sawn lumber cut directly from trees, dimensional lumber pieces are cut to standard sizes and grades. Dimensional lumber is typically identified by its nominal size, which is slightly larger than the actual profile size of the lumber.

Let’s talk about nominal and actual sizes.

Difference between Nominal and Actual lumber dimension

Nominal dimensions are the size of the board when it is first cut from a tree and the actual dimension is the size of the wood once it is dried (either air-dried or kiln-dried) and planed.

When lumber is first cut from a log it is cut to 2″ by 4″ (or whichever regular dimension it is supposed to be). But after it is cut, it dries and shrinks. Once it is dry, it goes through a planer tool which trims it to an actual dimension of 1 1/2″ x 3 1/2″ dimension.

You can still find nominal dimension lumber at a sawmill and dry and mill it down yourself using a planer and jointer.

For everyday woodworkers and DIYers, it is easier to pick up a board off the shelf in a big box home improvement store or lumber yard.

Also note – this sizing nomenclature is used for softwoods like fir, pine, redwood, cedar, etc. Softwoods come from coniferous trees and are sold by the piece or by linear foot (price per foot of the board).

Hardwoods like oak, cherry, maple, and walnut that come from deciduous trees are sold using a different nomenclature we will discuss below.

Nominal vs Actual Wood Size Chart

Here are the common nominal and actual sizes of dimensional boards you will see in woodworking plans:

Get a downloadable version of the size chart here.

Hardwood Sizes

While you can find some hardwood in home improvement stores that are sold using the nominal sizing discussed above, a lumber store typically sells them using different identifiers.

There are two types of identifiers you will see with hardwood lumber:

• The thickness is denoted by 4/4, 6/4, 8/4, etc.
• The number of planed sides – denoted by S1S, S2S, etc.

The thickness of hardwood lumber

Hardwood thickness is typically denoted by quarter. Each quarter is 1/4″ thick. So essentially, when we talk about the thickness of the board, we are talking about the number of quarters of an inch thick the board is.

For example:

• 4/4 (spoken as four quarter) is 4 x 1/4″ = 1″ thick.
• 6/4 (spoken as six-quarter) is 6 x 1/4″ = 1 1/2″ thick.
• 8/4 (spoken as eight-quarter) is 8 x 1/4″ = 2″ thick.

However, just like nominal and actual sizing for softwoods above, there is one more identifier that decides the actual thickness – the smoothness of the board.

Number of sides planed for hardwood lumber

The sawmill that cuts lumber from a log is very aggressive and results in “rough-sawn” lumber with very rough surfaces. The lumber needs to be planed to be smooth and flat before it can be used in a project.

Lumber yards may plane a few surfaces before selling the boards to give you a head start.

As a result of the surfacing, the board loses thickness which results in the actual size being slightly smaller than the nominal size.

For example, an S1S 4/4 board is 7/8″ in actual thickness. See the hardwood lumber thickness chart below for more details.

Hardwood widths

Hardwood is usually available in random widths, but you can potentially find widths that are close to the standard widths of dimensional lumber.

Hardwood Lumber Sizing Chart

Get a downloadable version of the size chart here.

Plywood Dimensions

Plywood sheets are available in thicknesses ranging from 1/8″ all the way to 1″.

1/8″, 1/2″, and 3/4″ are the most commonly available. Similar to dimensional lumber, sanding and smoothing plywood in the manufacturing process removes material reducing the actual thickness of the sheet of plywood.

Plywood comes in large sheets with the full sheet of plywood being 4 feet x 8 feet but you can also buy smaller sizes at home improvement stores.

Now you know exactly what lumber sizes mean – whether it is softwood or hardwood, home improvement store, or lumberyard. You also know that nominal sizes and actual sizes are different which means you always want the actual measurements of your boards before starting on a project so you can adjust for the differences accordingly and have the correct size and amount of lumber for your next project.

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