What Is Dimensional Lumber?

If you’d like to embark on a building project, it’s important to understand what dimensional lumber is and how to purchase it. With so many different types of lumber available on the market, it can be overwhelming to choose the right one for your needs. 

Fear not, as we’re here to break down the basics of dimensional lumber, provide examples of sizes, explain the different grades, and list some of the most common applications for this particular type of lumber.

Definition of Dimensional Lumber

Dimensional lumber is wood that has been cut and milled to specific standardized sizes. Unlike rough-sawn lumber, which is unprocessed and irregularly shaped, dimensional lumber is smooth and uniform in size. The most common sizes of dimensional lumber are 2×4, 2×6, 4×4, and 6×6, but it can be found in a variety of other sizes as well.

A Note on Dimensional Lumber Sizes

Please note that the sizes listed above are nominal sizes and don’t reflect the exact measurements of the lumber. For instance, a 2×4 piece of dimensional lumber actually measures around 1 ½  inches by 3 ½  inches. Here’s a cheat sheet: 

Nominal SizeActual Size
1×1¾” x ¾” 
1×2¾” x 1 ½”
1×3¾” x 2 ½”
1×4¾” x 3 ½”
1×6¾” x 5 ½”
1×8¾” x 7 ¼”
1×10¾” x 9 ¼”
1×12¾” x 11 ¼”
2×21 ½” x 1 ½”
2×31 ½” x 2 ½”
2×41 ½” x 3 ½”
2×61 ½” x 5 ½”
2×81 ½” x 7 ¼”
2×101 ½” x 9 ¼”
2×121 ½” x 11 ¼”

This discrepancy arises from the initial sizing process and the natural shrinkage that wood undergoes after being cut and dried. It’s crucial to keep these actual dimensions in mind when planning and designing your projects to ensure accurate fits and joints.

Dimensional Lumber Grades

Dimensional lumber is available in five different grades: 

  • Select is the highest quality, with few knots and a smooth surface.
  • #1 has more knots than select, but still has a smooth surface.
  • #2 has even more knots than #1 and may have some slight warping.
  • Stud is used for internal framing, and has even more knots and imperfections than #2. 
  • Utility is the lowest quality and is used for construction projects where appearance is not a concern.

What Is Dimensional Lumber Best Used For?

The applications of dimensional lumber are virtually limitless. From framing the skeleton of a building to creating load-bearing walls, floors, and roofs, this type of lumber forms the backbone of most construction projects. Its versatility extends to outdoor projects like decks, pergolas, fences, and even landscaping features.

Thanks to its standardized dimensions and reliable structural properties, dimensional lumber provides consistency and ease of use for builders, contractors, and savvy DIY homeowners. Its availability in a wide range of lengths also ensures compatibility with various project requirements.

How to Purchase Dimensional Lumber

When purchasing dimensional lumber, it’s important to choose the right length, width, and thickness for your specific project. Be sure to measure carefully, factor in any necessary cuts or waste, and remember what was mentioned earlier in the article — a 2×4 is not actually 2×4 inches! 

You’ll also want to consider the grade and type of wood you need, as well as any treatment or finish that may be necessary to protect it from the elements. For more information on types of lumber and lumber grades, read these two articles: 

Shop Dimensional Lumber at Standard 

We’ve been West Michigan’s trusted, local source for lumber for over 100 years. With five full-service lumber yards, we have the inventory you need in the convenient location you need it. Stop by one of our locations and let one of our specialists help you find the type, grade, and size of lumber you need for a successful project.