Plywood Calculator

This plywood calculator was built to estimate the number of plywood sheets required for a project, whether you are sheathing a roof, covering a wall, or laying subfloor. Enter the length and width of the surface area to calculate your plywood needs.

How plywood is made & sold

Plywood is an extremely common building material incorporated into many types of construction projects. It is often used as roof sheathing, flooring, and exterior walls.

Plywood boards are made from compressed pieces of waste wood, or thinly sliced veneers. The pieces are layered with an alternating grain pattern and secured with adhesives to create a bond stronger than the wood itself. The alternating layers form a durable, shrink and warp-resistant building material.

However, not all plywoods are created equal. Variations in grading standards and quality are common between brands. Always make sure to check the specific properties of the plywood before you purchase it.

Common sizes

Plywood is measured in two dimensions: by length & width, and by thickness. The majority of plywood is used for roof sheathing, exterior walls, and subflooring. Because the spacing between trusses, joists, or studs is most often 16 in or 24 in, standard plywood is sized so the seams will fall on a support for fastening.

Width & length

Plywood is most commonly sold in sheets of 4 feet by 8 feet (about 1.2 by 2.4 meters), especially at home improvement stores. Wholesale or specialty suppliers often carry more sizes.

Common width & length:

• 4 ft x 8 ft (most common)
• 4 ft x 10 ft
• 4 ft x 12 ft
• 5 ft x 5 ft

Thickness

The thickness of plywood is also an important factor. Building codes will typically specify the thickness required for specific applications, with different thicknesses allowed depending on the spacing of the studs, joists, or trusses, the material used to cover it, and the fasteners used.

Common thickness:

• 1/4 in
• 3/8 in
• 1/2 in
• 5/8 in
• 3/4 in

For subflooring and roof sheathing -- especially asphalt shingle roofs -- 5/8 in is the most common (often sold as 23/32 in). Exterior walls are commonly 1/2 in (often sold as 15/32 in).

Exposure ratings

Depending on the materials, types of adhesives, and how it is engineered, plywood can be rated for different uses or exposure to the elements.

Plywood grades

Plywood is also graded based on its appearance. The grade is not typically a reflection of its structural integrity. There are four main grades of plywood: A, B, C, D, and CDX.

CDX is another popular grade, where one side of the sheet is C-grade, and the other is D-grade. The "X" indicates that it's designed for exposure to some moisture. It is typically the cheapest plywood available, and often used for applications where it won't be visible, like roof and wall sheathing or temporary jobsite structures.

Written by