Plywood and Sheathing Calculator

Thirty-two square feet a sheet, and the plan decides the rest. Area over 32 is the floor of the count; the layout is the ceiling. Sheets run with their long edge across the joists and stagger by half a sheet each row, so the last row and the last sheet in every row are cuts, and a floor whose width is not a multiple of 4 feet wastes a strip per row. The 10% here covers that on a plain rectangle; a roof with hips and valleys wants 15.

Fasteners are a schedule, not a guess. How many nails or screws a sheet takes depends on the spacing the structural notes or the panel manufacturer call for — commonly closer along the edges than in the field — and on the support spacing under it. Count one sheet from your schedule and enter it; the page multiplies. It offers no default because a default would be a structural claim.

Tongue-and-groove and 4 × 9. T&G subfloor loses about half an inch of width to the tongue, so the sheets cover a little less than 32 square feet; the page ignores that, and the waste allowance absorbs it. Wall sheathing on 9-foot walls is sold in 4 × 9 to avoid the horizontal joint; choose it above and the rows follow.