Plywood Calculator
Calculate how many sheets of plywood or OSB you need for subfloor, roof sheathing, wall sheathing, or cabinet projects. Get sheet count, square footage, and waste-adjusted totals.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Plywood Calculator | Sheets = Total Area / Sheet Area x (1 + Waste%) | 4x8 sheets |
Step-by-Step Examples
24x20 ft floor, 4x8 sheets, 10% waste.
- Area = 480 sq ft
- Sheets = (480/32) x 1.10 = 16.5 -> 17 sheets
- Standard 3/4-inch tongue-and-groove plywood for subfloor
30x25 ft plan area, pitched roof (pitch mult 1.118 for 6/12), 10% waste.
- Plan area = 750 sq ft
- Actual roof area = 750 x 1.118 = 838.5 sq ft
- Sheets = (838.5/32) x 1.10 = 28.8 -> 29 sheets
Perimeter of 40x28 ft house, 9 ft walls, subtract openings.
- Perimeter = 136 ft | Wall area = 136x9 = 1,224 sq ft
- Minus doors/windows (est 200 sq ft) = 1,024 sq ft
- Sheets = (1,024/32) x 1.10 = 35.2 -> 36 sheets
Real-World Applications
Common Mistakes to Avoid
A 6/12 roof has 11.8% more actual area than plan area. Always apply the pitch multiplier before calculating roof sheathing sheets.
Plywood sheets are 4x8 ft. If your room is 10 ft wide, each row requires 1.25 sheets (one full sheet + a strip from a second). Calculate actual layout, not just division by 32 sq ft.
Use Structural 1 or rated sheathing for roofs and floors. Cabinet-grade plywood for furniture and cabinets. Mixing grades can result in code violations for structural applications.