CalculatorEnter your measurements below and it works the answer out.
Area divided by the panel, plus 10% waste, rounded up to whole sheets. Plywood and OSB come in the same sizes, so the count is the same for either.
The arithmetic. Work out the area, divide by what one sheet covers, add 10% waste, round up. Nothing more than that — the value of the page is the coverage figures and the waste allowance, both of which are stated here rather than hidden inside the tool.
Why the waste allowance is 10%. Plywood and OSB are both sold as 4 × 8 sheets covering 32 square feet, so the count is the same whichever you use. Thickness changes the price and the span, not the sheet count.
How it is sold. Full sheets are 4 × 8 ft. Most stores also cut handy panels at 2 × 4 and 2 × 8, which cost more per square foot but fit in a car.
Think in whole sheets, and in which direction they run. Subfloor and sheathing are laid staggered so the joints do not line up, and that stagger is where the offcuts go. Deduct only large openings; a sheet cut around a normal opening is mostly still used.
Round up to how it is sold. The result below shows three numbers: the raw quantity, the quantity after the 10% allowance, and the whole sheets to buy. You can see exactly where the rounding happened rather than being handed one figure.
Divide your area in square feet by the coverage of one sheet, then add 10% and round up. At 32 sq ft each, a 200 sq ft job needs 7.
10% is what this calculator adds. Plywood and OSB are both sold as 4 × 8 sheets covering 32 square feet, so the count is the same whichever you use. Thickness changes the price and the span, not the sheet count.
144 sq ft divided by 32 sq ft a sheet is 4.5 sheets, so 5 with 10% waste. Subfloor is usually laid staggered, which is where the waste goes.
Free to use on any site, including commercial ones. Paste this where you want it to appear — it keeps working when we update the figures.