Roof Sheathing Calculator
Calculate roof sheathing (plywood/OSB) sheet quantities from roof area. Enter dimensions and pitch for sheet count with waste and cut waste. Free, no signup.
Roof Area Calculator
Calculate actual roof surface area from plan dimensions and pitch
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Roof sheathing — did you know?
Standard sheet sizes
UK: 2440 × 1220mm (8 × 4 ft) = 2.98 m² per sheet. US: 4 × 8 ft = 32 sq ft. Thickness: 12mm (UK min for rafters at 400mm), 15mm (600mm centres), 18mm (UK general). US: 7/16" OSB standard, 1/2" or 5/8" for high wind.
Sheet calculation
Sheets = roof_area ÷ sheet_area × (1 + waste%). At 10% waste: 100 m² ÷ 2.98 × 1.10 = 36.9 → 37 sheets. For US: 2,236 sq ft ÷ 32 × 1.10 = 76.9 → 77 sheets.
Waste for sheathing
Standard: 10%. Hips/valleys: 15% (diagonal cuts waste more). Staggered pattern (recommended): 10-12%. H-clips between sheets on rafters for spacing and support.
Nailing schedule for sheathing
8d ring-shank nails at 150mm OC on edges, 300mm OC in field (UK: 50mm nails at 150mm edges, 300mm field). That is ~32 nails per 8×4 sheet. 1 box (5,000 nails) covers ~150 sheets.
Formulas used
Sheets needed
sheets = ceil(roof_area ÷ sheet_area × (1 + waste%))
Sheet area (metric)
2.98 m² per 2440×1220mm sheet
Sheet area (imperial)
32 sq ft per 4×8 sheet
Nails
nails = sheets × 32
Frequently asked questions
How many sheets of plywood do I need for a roof?
roof_area ÷ sheet_area × (1 + waste%). 100 m² at 10% waste: 100 ÷ 2.98 × 1.10 = 37 sheets. US: 2,236 sq ft ÷ 32 × 1.10 = 77 sheets.
What thickness for roof sheathing?
UK: 12mm min at 400mm centres, 15mm at 600mm. US: 7/16" OSB standard, 5/8" for high wind zones. Check span ratings on panel stamp.
How much waste for roof sheathing?
10% standard, 15% for roofs with hips/valleys (diagonal cuts). Staggered patterns: 10-12%.
Best free roof sheathing calculator?
One that calculates sheets, nails, and waste from roof area. This tool does all, free.