Plywood Sheet Calculator — How Many Sheets Do I Need?
Calculate the number of plywood or OSB sheets needed for any project — subfloor, wall sheathing, roof decking, or shelving. Enter total area or length × width.
How to Use This Calculator
- Enter your total project area in square feet, OR enter the length and width
- Select the sheet size you plan to purchase
- Adjust the waste factor (10% for simple projects, 15–20% for complex cuts)
- Click "Calculate Sheets" to see how many to buy
How the Calculation Works
sheet_area = sheet_length_ft × sheet_width_ft
// 4×8 = 32 sqft | 4×10 = 40 sqft | 4×12 = 48 sqft
sheets_needed = ceil((total_area / sheet_area) × (1 + waste_factor)) Divide your total project area by the sheet size to get the minimum number of sheets, then add a waste factor for cuts and trimming. The 4×8 sheet is the most common size at 32 square feet. Always round up to whole sheets since you cannot buy partial sheets.
Variables:
- sheet_area: Area of one sheet in square feet (4×8 = 32 sqft)
- total_area: Total project area in square feet
- waste_factor: Extra material percentage for cuts and waste (typically 10%)
- sheets_needed: Total sheets to purchase, rounded up to whole sheets
Pro Tips
- A standard 4×8 sheet covers 32 sq ft — always add 10% for cuts and waste
- For subfloors: use 3/4" tongue-and-groove plywood or OSB for spans up to 16" OC
- Stagger panel joints when sheathing walls or floors to improve racking resistance
- Store plywood flat and off the ground to prevent warping before installation
- OSB is more economical than CDX plywood for structural applications like sheathing and subfloor
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Frequently Asked Questions
How many sheets of plywood for a 12×16 room subfloor?
A 12×16 room is 192 square feet. With 4×8 sheets (32 sqft each): 192 ÷ 32 = 6 sheets exactly. Add 10% waste = 6.6, rounded up to 7 sheets. Always round up — you cannot buy half sheets.
What thickness plywood do I need for a subfloor?
For 16" OC joists: 3/4" (23/32") tongue-and-groove plywood or OSB. For 19.2" OC: 3/4" is still fine. For 24" OC: use 1-1/8" (29/32") T&G plywood. Check your local building code for specific requirements.
How much does a sheet of plywood cost?
Prices vary by type: 3/4" CDX plywood typically runs $40–$60/sheet. 3/4" OSB (subfloor grade) is often $30–$45/sheet. Sanded pine plywood for shelving runs $50–$80/sheet. Baltic birch (cabinet grade) can be $80–$150/sheet.
Is OSB as strong as plywood for sheathing?
For structural applications like wall sheathing, roof decking, and subfloor, OSB meets the same code requirements as plywood and costs less. For applications with moisture exposure or where edge swelling is a concern, plywood is more durable.
What is the difference between CDX and sanded plywood?
CDX has rough C and D face grades and is for structural, hidden applications (sheathing, subfloor, roof deck). Sanded plywood (AC, BC) has a smooth face for visible applications like shelving, cabinetry, and furniture.