Quick answer: A standard 4x8 sheet of plywood or OSB covers 32 square feet. Divide your roof or wall area by 32 and add ~10% for waste to get the number of sheets.
This sheathing calculator finds how many 4x8 plywood or OSB sheets you need for roof or wall sheathing, plus fasteners and estimated cost, with a built-in waste factor.
Sheathing is the layer of structural panels — plywood or OSB — that covers your roof rafters or wall studs before the finish material goes on. Estimating it is simple: find your total area and divide by the coverage of one sheet.
Nail sheathing about every 6 inches along the panel edges and 12 inches in the field — roughly 60 nails per 4x8 sheet, or about 1 pound of nails for every 3 to 4 sheets. Leave a 1/8-inch gap between panels so they can expand with humidity without buckling.
Divide the total area you're covering by the coverage of one panel. A standard 4x8 sheet covers 32 square feet, so divide your square footage by 32 and add 10% for waste and cuts.
Divide the total roof area (including the pitch factor) by 32 square feet per sheet, then add about 10% for waste. A 1,600 sq ft roof needs roughly 50 sheets plus waste.
Roof sheathing is typically 7/16-inch OSB or 15/32-inch plywood for rafters 24 inches on center. Wall sheathing is usually 7/16-inch OSB. Subfloors use thicker 3/4-inch tongue-and-groove panels.
Roof and wall sheathing is nailed roughly every 6 inches along panel edges and 12 inches in the field, which works out to about 60 nails per 4x8 sheet, or roughly 1 pound of nails for every 3 to 4 sheets.
Yes. Leave about a 1/8-inch gap between panels (the thickness of an 8d nail) so they can expand with humidity without buckling. Many OSB panels have spacer lugs built into the edges.
Both are code-approved structural panels. OSB is cheaper and more uniform; plywood is lighter, dries faster if it gets wet, and holds fasteners slightly better. Most new construction uses OSB.
Every constant this calculator uses and where it comes from, so you can check it rather than take our word for it.
Local codes amend the model IRC and adopt different cycles — your building department governs. Manufacturers revise yields; where your product's data sheet disagrees with a default here, use the product's number. See our full methodology.