Subfloor Plywood Calculator

Calculate how many 4×8 sheets of plywood or OSB you need for a subfloor or sheathing job. Enter the area to cover and a waste allowance.

4 x 8 sheet
Sheets Needed
— 4×8 sheets
Rounded up.

Usage Tip

Add more waste for diagonal layouts, many obstructions, or complex room shapes.

THE MATH
sheets = round up( area × (1 + waste ÷ 100) ÷ 32 )
Each 4×8 sheet covers 32 square feet
A subfloor or wall-sheathing job is covered with 4-foot by 8-foot sheets, each spanning 32 square feet.
A waste allowance covers cuts, offcuts, and mistakes so you buy enough.
Enter the total area to cover and a waste percentage (10 percent is typical).
The result is rounded up to whole sheets.
For 4×12 sheets, divide the sheet count by 1.5.
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.