Plywood Calculator
A plywood calculator works out how many sheets you need by dividing the area you are covering by the area of one sheet. A standard 4 by 8 foot sheet covers 32 square feet, so divide your square footage by 32 and add waste. Enter your area below to get the plywood sheet count for subfloor, sheathing or roof decking.
Enter your area to see the sheets needed.
How Do You Calculate How Much Plywood You Need?
To calculate plywood, find the area you are covering (length times width), then divide by 32, the square footage of a standard 4 by 8 foot sheet, and add 10 percent waste. A 16 by 20 foot subfloor is 320 square feet, which is 10 sheets, or 11 with waste. The calculator works for floors, walls and roofs, and lets you choose other sheet sizes if your material differs.
What Size Is a Sheet of Plywood?
A standard plywood sheet is 4 feet by 8 feet, covering 32 square feet, and comes in thicknesses from 1/4 inch to 3/4 inch and more. The thickness depends on the use: 3/4 inch for subfloors, 1/2 inch for walls, and varying thickness for roof sheathing. The sheet area stays 32 square feet regardless of thickness, so the count is driven by area, which the calculator uses.
How Much Plywood Waste Should You Add?
Add about 10 percent waste for plywood, to cover cuts around openings, the offcuts at room edges, and the staggered seams that good installation requires. Complex layouts with many openings (doors, stairwells, vents) waste more, so 15 percent is safer there. The calculator defaults to 10 percent and lets you raise it, ensuring you have full sheets rather than coming up short mid-job.
Frequently asked questions
- How many sheets of plywood do I need?
- Divide your area by 32 (a 4 by 8 sheet) and add 10 percent waste. A 320 square foot subfloor needs about 11 sheets.
- What size is a sheet of plywood?
- A standard sheet is 4 by 8 feet, covering 32 square feet, in thicknesses from 1/4 to 3/4 inch and up. The area stays 32 square feet regardless of thickness.
- How much plywood waste should I add?
- About 10 percent for normal layouts, 15 percent for complex areas with many openings, to cover cuts and staggered seams.