Plywood Calculator

A standard 4x8 foot sheet of plywood covers 32 square feet. This is the most common plywood size used in residential construction for subfloors, wall sheathing, and roof decking. Divide your total area by 32 and round up to find the number of 4x8 sheets needed. Always add a waste factor of at least 10% before dividing.

4x9 sheets (36 square feet each) are used when the floor-to-ceiling height or wall height is greater than 8 feet, particularly in rooms with 9-foot ceilings. They are also used for wall sheathing on taller walls to reduce the number of horizontal seams. 4x12 sheets (48 sq ft) are used for tall commercial walls. Check availability at your local lumber yard, as 4x9 and 4x12 are less commonly stocked than 4x8.

The most common subfloor plywood thickness is 3/4 inch (23/32 inch actual). For floor joists spaced 16 inches on centre, 3/4 inch plywood is standard. For joists at 24-inch centres, 3/4 inch or thicker is required. The American Plywood Association (APA) panel rating system indicates the recommended joist spacing on each panel. Always check local code requirements for your specific application.

No. OSB (oriented strand board) and plywood are both structural wood panel products, but they are made differently. Plywood is made from thin veneers glued at alternating grain angles. OSB is made from compressed wood strands. For most structural applications such as subfloor, wall sheathing, and roof sheathing, they are interchangeable per building codes. Plywood is generally more moisture-resistant and is preferred in wet applications.

A standard 3/4 inch, 4x8 foot plywood sheet weighs approximately 60 to 65 pounds (27 to 29 kg). Thinner 1/2 inch sheets weigh approximately 40 to 45 pounds. OSB of the same thickness weighs slightly more. Weight is an important consideration when working alone or in tight spaces. For large roofing or subfloor jobs, plan for multiple people or use mechanical assistance to lift panels into position.