Dimensional lumber is a construction term for wood that is cut to standard sizes for building or crafting purposes. Learn more about the different sizes and uses of dimensional lumber in this easy-to-understand guide!
If you’re getting into DIY projects like home renovations or crafting projects, you’re going to need to know the basics of dimensional lumber. Not all wood is interchangeable in different projects, and knowing the difference between dimensional lumber, rough-cut lumber, and other common lumber terms can help you nail your projects on the first try and make you more confident in designing projects of your own. Look at this as a beginner’s guide to dimensional lumber, including common dimensional lumber sizes and the actual sizes of dimensional lumber, hardwood versus softwood, and other stuff you should know before hitting the hardware store.
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What Is Dimensional Lumber?
Dimensional lumber is pre-cut wood that comes in a range of standard sizes. Unlike rough-cut or sawn lumber, it’s been processed by planing and sanding so the four sides are smooth and finished to the “final” thickness. What you see is what you get unless you decide to cut it down further to fit your project, whereas sawn lumber will have to be milled and will reduce in size before being used.
Dimensional lumber is typically referred to as its approximate width and length in inches, like a 2×4, for example.
This is important: A 2×4 IS NOT ACTUALLY 2″ x 4″!
Dimensional lumber can be made of treated or untreated and hard or soft woods. You’ll pick the type of wood based on what you’re using it for, like framing a wall, DIY home decor projects, garden boxes, etc. You can find it in nearly any home improvement store or lumber yard.
One thing that’s important to note is that dimensional lumber isn’t actually the size it’s named as – a 2×4 is actually closer to 1 ½ by 3 ½ inches. This can mess with your measurements, especially in a project that demands precision, so keep this in mind when you’re working with dimensional wood. You can find the actual dimensions of the lumber by using a tape measure or straight edge to measure it.
There are also a few general rules of thumb that you can use to guesstimate the actual dimensions of most standard dimensional lumber.
- For dimensional lumber less than 1” in thickness, subtract ¼ inch from the dimensions.
- Subtract ½ inch from dimensional lumber between 2-8”.
- If your lumber is 8” thick or larger, subtract ¾ inches.
You’ll want to double-check the measurements with a measuring tape to make sure they’re right for your project, especially for more technical projects, but knowing these estimates can help in a pinch. There are a mix of answers about the real size of a 8×10, for example, so the 8×10 may follow the 1/2″ rule in some cases.
Hardwood vs. Softwood Dimensional Lumber
Hardwood and softwood dimensional lumber are suited to different purposes. Hardwood dimensional lumber is made from hardwood trees and has a denser wood grain, making it more resistant to moisture, pests, and decay than softwood. Softwood is usually less expensive and can be a good choice for projects that aren’t exposed to as much wear, weight, or moisture. Both hardwood and softwood boards can be treated or untreated. Make sure to carefully read hardware store labels so you know what you’re taking home is right for you!
Standard Dimensional Lumber Sizes and Uses
There’s usually a large range of common dimensional lumber sizes available at your hardware store.
Here’s a quick introduction to some of the usual suspects and what you can use them for… please keep in mind that the ‘actual size’ is possibly not going to be accurate for your wood. You ALWAYS should check:
1×2 – Actual Size: 0.75×1.5″ – These are good for craft projects, as well as using for decorative elements such as cabinet trim or to cover the raw edges of 3/4″ plywood.
1×4 – Actual Size: 0.75×3.5″ – Another thin wood that’s good for craft projects and small furniture projects.
2×2 – Actual Size: 1.5 x 1.5″ – Small square posts like the 2×2 (or smaller posts starting at 1×1) can be used in furniture making, craft projects like picture frames, and smaller home and garden projects.
2×4 – Actual Size: 1.5 x 3.5″ – 2x4s are typically used for wall framing and other types of construction. The studs in your walls are often made of 2x4s. They’re also good for constructing things like decks, interior and patio furniture, garden boxes, shelving, framing, and various other projects.
2×6 – Actual Size: 1.5 x 5.5″ – You can use 2x6s to build decks, make table tops, construct boxes, and create nearly anything that requires sturdy, wide boards.
4×4 – Actual Size: 3.5 x 3.5″ – 4x4s make strong posts for small projects that require a sturdy base. Think deck posts, small sheds, heavy duty cabinets bases, retaining walls, and other similar projects.
4×6 – Actual Size: 3.5 x 5.5″ – Anything above a 4×6 can be used to create heftier versions of your 2×6 or 4×4 projects, like rustic farmhouse tables, outdoor structures, and more.
4×8 – Actual Size: 3.5 x 7.5″ – Large 4×8 beams can be used to build cabins, sheds, fireplace mantels, faux (or real) exposed roof beams, and other large-scale projects that require the wood to bear lots of weight.
6×6 – Actual Size: 5.5 x 5.5″ – These are sturdy square posts that can be used to make things like string light or lantern posts, large decks, pole barns, and other large-scale projects.
6×8 – Actual Size: 5.5 x 7.5″ – 6x8s are commonly used as support beams in basements, pergolas, large gazebos, barns, and more.
6×12 – Actual Size: 5.5 x 11.25″ – 6x12s are typically used in large construction projects like home building.
8×8 – Actual Size: 7.5 x 7.5″ – One of the heftiest square pieces of dimensional lumber, 8x8s are great for your heaviest construction projects.
8×12 – Actual Size: 7.5 x 11.25″ – 8×12 is one of the largest dimensional beam sizes available in normal home improvement stores like Home Depot. These boards can be used for big projects or “ripped” (cut) down to make smaller wood beams.
Standard Dimensional Lumber Chart
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