Roof Decking Calculator
Calculate roof decking (sheathing) panels needed for your roof. Accounts for roof pitch, waste, and standard 4ร8 sheet size.
๐ Roof Decking Calculator
Results
Flat Area720.00 sq ft
Pitch Multiplier1.118
Actual Roof Area804.98 sq ft
Total (+ waste)885.48 sq ft
4x8 Sheets28 sheets
๐ก How to Calculate Roof Decking
Roof decking area is larger than the footprint because of the pitch. Multiply the flat area by the pitch factor: โ(1 + (pitch/12)ยฒ). A 6/12 pitch increases area by 11.8%. Common decking is 4ร8 ft CDX plywood or 7/16-inch OSB (32 sq ft per sheet).
Add 10โ15% for waste โ more for complex roof shapes with valleys, hips, and dormers. Decking must be staggered (joints offset by at least 4 feet) and fastened with 8d nails every 6 inches on edges and 12 inches in the field.
A 30ร24 ft gable roof at 6/12 pitch: flat area = 720 sq ft ร 1.118 = 805 sq ft. With 10% waste = 886 sq ft รท 32 = 28 sheets of 4ร8 plywood or OSB.