The 4×8 sheet is the unit of everything
Plywood, OSB, MDF and beadboard all ship in 4×8 sheets covering <strong>32 square feet</strong> — walls, subfloors and roof decks all convert the same way. The calculator adds 10% waste for the cuts around windows, doors and electrical boxes.
Orientation and thickness matter
Structural panels (subfloor, roof and wall sheathing) must run their long face perpendicular to supports with edges staggered — the waste percentage assumes that pattern. Thickness follows the use: 1/4 inch for cabinet backs, 23/32 tongue-and-groove for subfloors, 7/16 OSB or 1/2 ply for wall sheathing.