Plywood calculator
Work out how many sheets of plywood or OSB an area needs, with an allowance for cut layout loss.
Plywood calculator
Work out how many sheets of plywood or OSB an area needs, with an allowance for cut layout loss.
Enter the area length and width to see how many sheets you need.
Sheets needed
Project summary
How it works
This is a coverage estimate for a standard 4 by 8 ft sheet with a cut layout waste allowance. Sheet thickness, span rating and fastening pattern depend on the application and local code.
Plywood calculator
Why sheet goods carry a bigger waste allowance
Plywood and OSB are sold as full 4 by 8 foot sheets, 32 square feet each, and a room or roof plane rarely divides evenly into that shape. Every sheet that runs into a wall, a corner or a penetration leaves an offcut that is often too small to reuse, which is why this calculator uses a larger default waste allowance than a poured material like concrete or gravel: the loss here is layout loss from cutting, not shrinkage or spillage.
Buying whole sheets
The result always rounds up to a whole sheet, since a supplier does not sell three quarters of a sheet. A project needing 300 square feet at 32 square feet per sheet and a 10 percent waste allowance needs just over 10 sheets on paper, so the calculator returns 11: the whole sheet count that actually covers the area once cutting is accounted for, along with how much coverage that buys and how much of it is overage.
Frequently asked questions
How many sheets of plywood do I need for a given area?
Multiply the area by your waste allowance, divide by 32 square feet (a standard 4 by 8 foot sheet), and round up to the next whole sheet. This calculator does that automatically once you enter the length and width of the area to cover.
Does a bigger room need more waste allowance than a small one?
Not proportionally, but layout matters more than size. A long, narrow area or one with many corners and penetrations wastes more per square foot than a simple rectangle, regardless of total size, so it can be worth allowing extra on an irregular layout even if the area itself is modest.
How many sheets of plywood do I need for a 12 by 12 room?
A 12 by 12 room has 144 square feet of floor area, which takes four sheets of 4 by 8 foot plywood. Add 10 percent waste and you need about five sheets. The calculator gives you the exact count based on your room dimensions.
What thickness of plywood do I need?
Subfloor underlayment is typically 3/4 inch for floors and 1/2 inch for walls. Roof sheathing is usually 1/2 inch or 5/8 inch. The calculator shows the square footage so you can select the appropriate thickness for your application.
How much does a sheet of plywood cost?
Plywood prices vary by grade and thickness. CDX structural plywood costs 30 to 50 dollars per sheet. Finished plywood costs more. The calculator gives you the sheet count so you can price materials at your local supplier.
Can I use plywood for concrete forms?
Yes, CDX plywood is commonly used for concrete formwork. 3/4 inch plywood is standard for walls and 1/2 inch for curved forms. The calculator helps you estimate the quantity needed.
How do I calculate plywood for a sloped surface?
Measure the actual surface area of the slope, not the horizontal footprint. The calculator handles rectangular areas, and for slopes you can measure the length and width of the inclined surface directly.
What is the waste factor for plywood?
A 10 percent waste factor accounts for cuts and edge pieces. Complex layouts or diagonal installations may need 15 percent. The calculator lets you set the waste percentage.