Plywood Sheathing Calculator
Enter the total area you're sheathing — a roof, wall, or subfloor — to calculate how many standard plywood or OSB sheets you need, including a waste allowance.
How the Plywood Sheathing formula works
A coverage-based calculation using a standard sheet size:
Sheet area = Sheet width × Sheet length (commonly 4×8 ft = 32 ft²) Sheets needed = ceil( Total area × (1 + Waste%) / Sheet area )
Step-by-step calculation
- Calculate the total area to be sheathed.
- Divide by a single sheet's area (commonly 32 ft² for a standard 4×8 sheet).
- Increase by a waste percentage for cuts and round up to a whole sheet.
Worked example
A roof section totaling 960 ft², using standard 4×8 (32 ft²) sheets, with 10% waste: Sheets = ceil(960 × 1.10 / 32) = ceil(33) = 33 sheets.
Frequently asked questions
What's the difference between plywood and OSB for sheathing?
Both are commonly used structural sheathing materials with similar coverage math — plywood is made of thin wood veneer layers, while OSB (oriented strand board) is made of compressed wood strands. They differ in cost, moisture behavior, and some installation details, but the area-based calculation here applies to either.
Does roof sheathing need a different waste allowance than wall sheathing?
Roof sheathing often needs a bit more waste allowance than flat wall sections due to angled cuts at hips, valleys, and ridges — 10-15% is a reasonable range depending on roof complexity.