While plywood is sold as "4×8," the actual dimensions are often slightly smaller due to manufacturing tolerances.
A standard 4×8 plywood sheet typically measures 47-7/8" x 95-7/8" instead of the nominal 48" x 96".
When buying plywood for construction or renovation, it’s important to understand that the dimensions listed on the label are nominal sizes. The actual size will often differ by a fraction of an inch. This can affect fit, cuts, and overall project measurements. Let’s explore why plywood sizes vary and how it impacts your construction or DIY project.
Is 1/2 inch plywood actually 1/2 inch?
1/2" plywood typically measures around 15/32" (0.468") instead of the nominal 1/2" (0.500") thickness.
The thickness of plywood is not exactly what it says on the label due to sanding and compression during production. Standard plywood sheets are manufactured with slight variations in thickness. For example, 1/2" plywood is often closer to 15/32" or 0.468", while 3/4" plywood is usually around 23/32" or 0.718". These small differences can add up in large projects, so always measure your plywood with calipers before cutting or installing.
What is the actual size of a 4×8 post?
A “4×8” post, as with plywood, is typically smaller than the labeled size.
A 4×8 post generally measures 3-1/2" x 7-1/4", with the nominal 4×8 size referring to the post’s intended dimensions.
The nominal sizes for lumber (such as 4×4, 2×6, etc.) are rough cuts made before the lumber is planed and finished. After drying and finishing, the actual size of the post is smaller than what’s listed. For example, the commonly used "4×8" post actually measures 3-1/2" x 7-1/4", not 4" x 8". Always account for these differences when planning cuts or making connections in framing.
What are the actual dimensions of plywood?
While sold as "4×8", plywood typically measures a bit smaller in both width and length.
The actual dimensions of plywood are generally 47-7/8" x 95-7/8" for a nominal 4×8 sheet.
Manufacturers of plywood sheets use slight tolerances to allow for changes during the manufacturing and drying process. As a result, a nominal 4×8 sheet will typically be 47-7/8" wide and 95-7/8" long. This 1/8" difference can make a difference in precise fitting, so always plan your cuts and measurements accordingly. For example, when designing a project or installing plywood sheets for subfloors, make sure to allow for this minor variance.
Is 4×8 OSB exactly 4×8?
A 4×8 sheet of OSB typically measures 47-7/8" x 95-7/8", just like plywood.
OSB sheets, used for sheathing and subflooring, are typically made to the same nominal dimensions as plywood. The actual size of a 4×8 sheet of OSB will usually be 47-7/8" by 95-7/8". The minor difference in size comes from the same production tolerances that apply to plywood. For most construction applications, this slight variation won’t impact your project, but it’s always good practice to double-check dimensions when precise fitting is needed.
Conclusion
When buying plywood or OSB, always be mindful of actual sizes—they are often smaller than the nominal measurements. Knowing these details can help ensure a better fit for your construction or DIY project.