Plywood is a wood panel that is composed of several thin layers, or plies, of wood veneer. The veneers are glued perpendicular to each other, creating a cross-grain pattern that is much stronger than solid wood.
Plywood sheet goods are available in various thicknesses and sizes and are typically sold by their nominal thickness. While the length and width are often the actual dimensions, the nominal thickness is usually different than the actual thickness.
For example, a sheet of plywood with a nominal thickness of 3/4” is often less than 3/4” thick. This introduces challenges when precision measurements are needed, such as when selecting a router bit or sizing a dado saw blade.
What is the Actual Thickness of a Sheet of Plywood
Plywood is often sold in 1/4“, 1/2“, or 3/4” nominal thicknesses, but the actual thickness is often 1/32” thinner. Because the actual thickness may vary, measuring the plywood sheet using a caliper is the only accurate way to determine its thickness.
- A 3/4” sheet is actually 23/32” thick.
- A 1/2” sheet is actually 15/32” thick.
- A 1/4” sheet is actually 7/32” thick.
For some applications, such as sheathing a roof, the 1/32” difference is not important, but for fine carpentry, it may be critical to get grooves and cuts to be precisely the thickness of the plywood.
For example, a groove for cabinet door panel needs to be the exact thickness of the plywood, or the door will not be stable due to the loose fit of the parts, and it will likely rattle each time it’s opened or closed.
Precision is important for trim carpentry as well; when installing wainscoting panels, if a cut doesn’t match the exact plywood thickness the final result will have noticeable gaps.
Why is a 3/4” Sheet of Plywood Less Than 3/4” Thick?
There are a few reasons why the actual thickness of plywood varies. First, wood shrinks as it dries and moisture leaves the wood. This means that a sheet of plywood that started at 3/4” may shrink slightly after manufacturing.
It’s not just plywood; the actual size of dimensional lumber is also smaller than the advertised nominal dimensions for this reason as well.
Another reason for varying plywood thicknesses is the range of manufacturing tolerances. Sheets are available in hardwood or softwood veneers and in varying grades, including sanded and unsanded. These different grades have different manufacturing tolerances and may vary more or less from the 3/4” nominal thickness.
Plywood is almost always thinner than the nominal measurement due to the fact that most tooling in furniture and cabinet factories and manufacturing facilities can accommodate plywood that is thinner than expected but not thicker than expected. For this reason, it is very common to see actual thicknesses on the thinner side and rarely thicker than the nominal measurement.
A 3/4” (19 mm) sheet of plywood is typically 23/32” (18 mm).
Common Plywood Dimensions
Plywood is most often sold in 4′ x 8′ sheets, but may also be available in 4′ x 10′, 4′ x 12′, or 2′ x 4′ sheets. Hardwood plywood (e.g. birch, maple, oak, cherry, etc.) is often available in 4′ x 8′, 5′ x 5′, and 2′ x 4′ sheets.
MDF, or medium-density fiberboard, is another sheet good that is sold in 4′ x 8′ sheets. Usually, the actual dimensions of an MDF sheet are oversized by one inch, and the full sheet is typically 49″ x 97″.
You can use a plywood calculator to estimate the number of 4′ x 8′ sheets needed for a project.
Plywood is usually sold by the sheet, but in some rare cases, it may be sold by the board foot. Board footage is a measure of the volume of wood in the sheet, and to calculate it, you can use a board footage calculator or calculate the cubic inches and divide by 144.
Plywood Thickness Chart
|Nominal Thickness||Actual Thickness (inches)||Actual Thickness (millimeters)|
The weight of a panel will vary by thickness and type. Learn more about plywood weight for different types, including softwood, hardwood, marine-grade, OSB, MDF, MDO, and particle board.