Subfloor / Plywood Calculator
Estimate plywood or OSB sheets for subfloors, wall sheathing, and roof decks.
Sheets needed
11 sheets
320 sq ft floor/wall area
- Area with waste
- 352 sq ft
- Coverage / sheet
- 32 sq ft
- Estimated cost
- $495.00
- Before waste
- 10
Buy panels rated for your span and exposure. Quantity math is the same for plywood and OSB.
How this calculator works
Sheet goods are ordered by counting how many 4×8 panels cover the area. One panel is 32 square feet.
Stagger seams and follow span ratings for the thickness you choose - this tool only handles quantity.
sheets = ceiling(sq ft ÷ 32 × waste)
- Subfloors often use 3/4" tongue-and-groove
- Add waste for rips at walls and closets
- Confirm thickness with joist spacing span charts
Frequently asked questions
How many sheets of plywood do I need?
Divide the floor or wall area by 32 for 4×8 sheets, then add waste. A 320 sq ft room needs 10 sheets before waste.
What thickness subfloor should I use?
It depends on joist spacing and finish floor. Many 16" OC floors use 23/32" or 3/4" T&G panels - check local code and manufacturer charts.
OSB or plywood?
Both can work as subfloor/sheathing when rated for the span. Choose based on price, moisture exposure, and what your plans specify.
Related calculators
Keep planning your project with these tools, or browse the Roofing & Framing category.