Nominal vs. Actual Sizing
Kreg Tool Tips: Wood Buying by
Kreg Tool Company
When you’re buying lumber at a home center, whether it’s in the “outdoor,” “construction,” or “board” aisle, you need to understand that the stated size and the actual size of the boards are generally not the same. That’s because all construction lumber, along with essentially every type of “board” sold in a home center, has a stated or “nominal” thickness and width, and a slightly smaller “actual” thickness and width. For example, a 2x4 board actually measures 11/2" thick x 31/2" wide, as shown in the table below.
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Here’s what that means to you:
If you are using a project plan, like the ones that come with your DIY Project Kit, the materials list may say to buy a 1x4 (the nominal size), but the dimensions in the plan will base everything on that board’s actual size — 3/4" x 31/2" in this case.
If you are drawing your own project plan, make sure that you use the actual dimensions for all of the boards. If you accidentally design your project using the nominal dimensions, it may not go together as you had planned.