Roof Sheathing Calculator
Estimate project materials from measurements and product coverage. Verify requirements before ordering.
Calculate materials
Planning estimate only; check local codes and product specifications.
Measure each roof plane along its slope
- Enter the length and slope width of one roof plane in feet. Do not substitute horizontal footprint width.
- Enter sheet coverage in square feet and a project-specific cutting allowance.
- Calculate each additional plane separately and combine quantities for panels of the same specification.
Roof Sheathing Calculator: formula and assumptions
Sheets = roof length × slope width × (1 + waste ÷ 100) ÷ sheet area, rounded up.
Worked calculation
One 40 × 20 ft roof plane, 32 ft² sheets and 10% waste requires 28 sheets. With zero waste it requires 25 sheets.
What this estimate includes
Measure width along the roof slope. Calculate each roof plane separately; the tool does not automatically double for two sides. Thickness, fastening and structural rating require separate verification.
Planning details that change the estimate
The tool does not automatically double the result for a gable roof. Hips, valleys, dormers and openings can increase cutting losses. Sheet area alone cannot specify thickness, span rating, edge support or fastening. Check these against the roof design before ordering panels.
Roof Sheathing Calculator FAQs
Does this include both sides of a roof?
Only if your entered dimensions already represent the combined measured area. Otherwise calculate each plane separately.
Should I enter horizontal width?
No. Use width measured along the sloping roof surface.
Does zero waste produce a usable order?
It gives an area-only minimum. Actual layout and cuts may require more panels.
Continue planning this project
Review roof geometry with the Roof Pitch Calculator and Rafter Calculator. Estimate the separate roof covering with the Shingle Calculator.
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