Roof Plywood / OSB Calculator

Sheets, Waste Factor & Decking Coverage

Use the Plywood / OSB Calculator to figure out how many 4x8 sheets of roof sheathing you need to deck a roof. Enter total roof area and a waste factor (typically 10% for simple roofs, 15%+ for cut-up roofs) and the tool returns the sheet count. Standard sheets cover 32 sq ft each. Building code typically requires 7/16" minimum OSB or 15/32" plywood for 24" rafter spacing. Combine the result with our Underlayment and Drip Edge calculators to fully scope a re-deck or new build.