How many sheets of plywood do I need?
Sheets = (area − openings) × (1 + waste) ÷ sheet area, rounded up
A 20 × 12 ft floor is 240 sq ft. With 10% waste that is 264 sq ft, or 8.25 sheets of 4 × 8, so you buy 9.
Thickness by use
| Use | Typical panel |
|---|---|
| Wall sheathing | 7/16" OSB or 1/2" plywood |
| Roof sheathing, rafters 24" o.c. | 1/2" or 5/8" |
| Subfloor, joists 16" o.c. | 23/32" (3/4") tongue and groove |
| Subfloor, joists 24" o.c. | 7/8" or 1-1/8" |
| Shed floor | 3/4" tongue and groove |
Sheets by area
A 4 by 8 ft sheet covers 32 sq ft. The table rounds up and shows a count with 10% extra for cuts.
| Area | Sheets | With 10% waste |
|---|---|---|
| 64 sq ft | 2.00 | 3 |
| 100 sq ft | 3.12 | 4 |
| 120 sq ft | 3.75 | 5 |
| 200 sq ft | 6.25 | 7 |
| 320 sq ft | 10.00 | 11 |
| 480 sq ft | 15.00 | 17 |
| 800 sq ft | 25.00 | 28 |
Plywood is thinner than its label, as the lumber dimensions chart shows. For board-foot priced stock, use the board foot calculator.
Frequently asked questions
How many sheets of plywood for a 12x12 room?
Five 4 × 8 sheets with 10% waste (144 sq ft × 1.1 ÷ 32 = 4.95).
How many sheets for a 10x12 shed floor?
Five sheets of 4 × 8 with waste, or four if the layout lines up exactly with the joists.
Is OSB cheaper than plywood?
Usually, and it is rated for the same structural uses. Plywood handles repeated wetting and holds fasteners near edges better.
How many square feet is a sheet of plywood?
A standard 4 by 8 ft sheet is 32 square feet.
How many sheets of plywood for a 10 by 12 ft floor?
The floor is 120 sq ft, which is 3.75 sheets, so buy 4, or 5 with waste for cuts.
Reference charts
More lumber and wood calculators
Board Foot Calculator
Board feet and cost for any stack of lumber.
Stud Calculator
Studs and plates for any wall.
Firewood Cord Calculator
Check a woodpile in cords and face cords.
Log Weight Calculator
Green weight and Doyle board feet by species.
Lumber Cost Calculator
Price per piece, board foot and linear foot, side by side.
Log Board Foot Calculator
Board feet in a log by two log rules.