Plywood and Sheathing Calculator

Figure how many sheets of plywood or OSB you need to sheathe walls, a floor or a roof, including openings, roof pitch and waste.

What Are You Sheathing?

Wall Length (Ft.)

Total of all walls: the building's perimeter for exterior walls.

Wall Height (Ft.)

Openings (Sq. Ft.)

Doors and windows. Many builders sheathe over openings and cut them out; enter 0 to do the same.

Sheet Size

Extra for Waste (%)

Price per Sheet

Name

Fractions work too: try 8 1/2.

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Sheets

Area to cover
Sheets before waste
Coverage bought
Cost: Add a price to estimate

Sheathing List

Areas you add are saved in this browser.

Name	What	Area	Sheets	Cost	Remove

How to Figure Sheathing

Find the area to cover in square feet and divide by the area of one sheet: 32 for 4×8, 36 for 4×9 and 40 for 4×10. For walls, multiply the total wall length by the height and subtract openings if you won't sheathe over them. For a roof, multiply the footprint by the slope factor for the pitch to get the true roof area.

Sheets = area ÷ sheet area × (1 + waste), rounded up

Roof area = footprint × √(pitch² + 144) ÷ 12

Worked Example

Sheets per 100 Square Feet

Sheet	Area	Sheets per 100 Sq. Ft.	With 10% Waste

Tips for Sheathing

Taller sheets (4×9 or 4×10) can cover a wall from the sill to the top plate in one piece, which cuts seams and blocking. Leave a ⅛″ gap at panel edges and ends so panels can expand. Roofs with hips, valleys and dormers waste more, so allow 15% or more. Thickness, span rating and nailing schedule should follow your plans and local code.